¹Division of Dermatology, McGill University, Montreal, QC, Canada
²Brunswick Dermatology Center, Fredericton, NB, Canada
³Division of Clinical Dermatology & Cutaneous Science, Dalhousie University, Halifax, NS Canada
⁴Probity Medical Research, Waterloo, ON, Canada
⁵Department of Dermatology, Discipline of Medicine, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL, Canada
⁶Department of Dermatology and Skin Science, University of British Columbia, Vancouver, BC, Canada
⁷Division of Dermatology, University of Ottawa, Ottawa, ON, Canada
⁸Division of Hematology, Department of Medicine, McGill University, Montreal, QC, Canada
⁹Division of Dermatology, University of Alberta, Edmonton, AB, Canada
¹⁰Division of Dermatology, University of Toronto, Toronto, ON, Canada

Conflict of interest: Elena Netchiporouk has received grants, research support from Novartis, Sanofi, Sun Pharma, AbbVie, Biersdorf, Leo Pharma, Eli Lilly; speaker fees/honoraria from Bausch Health, Novartis, Sun Pharma, Eli Lilly, Sanofi Genzyme, AbbVie, Galderma, Novartis, Sanofi Genzyme, Sun Pharma, Bausch Health and Leo Pharma and consulting fees from Bausch Health, Novartis, Sun Pharma, Eli Lilly, Sanofi Genzyme, AbbVie, Galderma, Novartis, Sanofi Genzyme, Sun Pharma, Bausch Health and Leo Pharma. Irina Turchin served as advisory board member, consultant, speaker and/or investigator for AbbVie, Amgen, Arcutis, Aristea, Bausch Health, Boehringer Ingelheim, Celgene, Eli Lilly, Galderma, Incyte, Janssen, Kiniksa, Leo Pharma, Mallinckrodt, Novartis, Pfizer, Sanofi, UCB. Wayne Gulliver received grants/research support from AbbVie, Amgen, Eli Lilly, Novartis and Pfizer; honoraria for advisory boards/invited talks from AbbVie, Actelion, Amgen, Arylide, Bausch Health, Boehringer, Celgene, Cipher, Eli Lilly, Galderma, Janssen, Leo Pharma, Merck, Novartis, PeerVoice, Pfizer, Sanofi-Genzyme, Tribute, UCB, Valeant and clinical trial (study fees) from AbbVie, Asana Biosciences, Astellas, Boehringer-Ingelheim, Celgene, Corrona/National Psoriasis Foundation, Devonian, Eli Lilly, Galapagos, Galderma, Janssen, Leo Pharma, Novartis, Pfizer, Regeneron, UCB. Gizelle Popradi has received honoraria or speaker fees from Jazz Pharma, Seattle Genetics, Abbvie, Kite Gilead, Pfizer, Taiho, Servier, Novartis, Merck, Kyowa Kirin, Abbvie, Avir Pharma, Mallinckrodt. Robert Gniadecki reports carrying out clinical trials for Bausch Health, AbbVie and Janssen and has received honoraria as consultant and/or speaker from AbbVie, Bausch Health, Eli Lilly, Janssen, Mallincrodt, Novartis, Kyowa Kirin, Sun Pharma and Sanofi. Charles Lynde was a consultant, speaker, and advisory board member for Amgen, Pfizer, AbbVie, Janssen, Novartis, Mallincrodt, and Celgene, and was an investigator for Amgen, Pfizer, AbbVie, Janssen, Lilly, Novartis, and Celgene. Ivan V. Litvinov received research grant funding from Novartis, Merck, AbbVie and Bristol Myers Squibb and honoraria from Janssen, Bausch Health, Galderma, Novartis, Pfizer, Sun Pharma, Johnson & Johnson and Actelion. Topics included in this article were based on, but not limited to, broad discussions at an advisory board meeting, which was sponsored and funded by Mallinckrodt, Inc. Consultancy fees were paid to meeting participants (EN, IT, WG, JD, MK, RG, CL and IVL). All other authors declare no existing competing interests.

Abstract:
Extracorporeal photopheresis (ECP) is an immunomodulatory therapy that has been used for over 35 years to treat numerous conditions. ECP was initially approved by the US FDA in 1988 for the treatment of Sézary syndrome, a leukemic form of cutaneous T-cell lymphoma (CTCL). Although CTCL remains the only FDA-approved indication, ECP has since been used off-label for numerous other conditions, including graft-versus-host disease (GvHD), systemic sclerosis, autoimmune bullous dermatoses, Crohn’s disease, and prevention of solid organ transplant rejection. In Canada, ECP is mainly used to treat CTCL, acute and chronic GvHD, and in some instances systemic sclerosis. Herein, we review the current concepts regarding ECP mechanism of action, treatment considerations and protocols, and efficacy.

Key Words:
extracorporeal photopheresis, cutaneous T-cell lymphoma, S.zary syndrome, systemic sclerosis, graft-versus-host disease, safety.

Introduction

Extracorporeal photopheresis (ECP) is an immunomodulatory therapy that has been used for over 35 years to treat numerous conditions (Figure 1).^1,2 ECP was initially approved by the Food and Drug Administration (FDA) in the United States in 1988 for the treatment of S.zary syndrome (SS), a leukemic form of cutaneous T-cell lymphoma (CTCL) with an aggressive clinical course, characterized by a triad of circulating neoplastic T-cells, erythroderma, and lymphadenopathy.¹ Although CTCL remains the only FDA-approved indication, ECP has since been used as an off-label treatment for numerous other conditions, including graft-versus-host (GvHD) disease, systemic sclerosis (SSc), autoimmune bullous dermatoses, Crohn’s disease, and to prevent solid organ transplant rejection.^1,2 In Canada, ECP is mainly used to treat CTCL, acute and chronic GvHD, and in some instances systemic sclerosis (Tables 1-2). The goal of this article is to review the current concepts regarding ECP mechanism of action, treatment considerations as well as suggested treatment protocols and efficacy in CTCL, GvHD, systemic sclerosis and other skin diseases.

Table 1. The use of ECP by hospital and by city in Canada in 2020.

Table 2. The use of ECP by city and by indication in Canada in 2020.

ECP involves placing a catheter to gain access to the venous circulation and collecting blood via continuous or discontinuous cycles, which is then centrifuged to create a leukocyte-rich buffy coat. The isolated leukocytes are then placed in a sterile treatment cassette, injected with liquid 8-methoxypsoralen (8-MOP) and exposed to ultraviolet A (UVA) radiation. Afterwards, the photochemically-altered white blood cells are returned to the patient’s venous circulation (Figure 1).^1,2 The Therakos^® ECP machine (the only available unit for this treatment) represents an automated closed system. Each treatment lasts approximately 1.5-3 hours, and the scheduling and frequency of treatments depend on the disease being treated.

The exact mechanism of action of ECP remains unknown, however, in CTCL, it is believed that the procedure leads to DNA-crosslinking and apoptosis of pathogenic T cells induced by 8-MOP with UVA exposure, the differentiation of monocytes to dendritic cell that present tumor antigens from apoptotic lymphocytes, stimulation of anti-tumor immune responses, and shifting of immunoregulatory cytokines to Th1 cytokine profile, such as interferon-gamma and tumor necrosis factor (TNF) alpha, thus restoring the Th1/Th2 balance.^1-4 In particular, ECP targets mostly tumor cells since the absolute number of normal T cells remains relatively stable after the procedure.¹ Given its therapeutic benefit in transplant rejection and autoimmune diseases, ECP is also believed to have unique immunomodulatory properties generating needed responses in an autoimmune setting, which are thought to be similarly mediated by DNA-crosslinking and apoptosis of autoreactive leucocytes (natural killer (NK) and T cells) and induction of T-regulatory cells after treatment, although this phenomenon was not observed in patients with SS.² However, unlike immunosuppressive therapies, ECP is not associated with an increased risk of opportunistic infections.² In fact, ECP is overall well-tolerated, with no reports of post-treatment Grade III or IV side effects, as per the World Health Organization classification.² In particular, ECP is not associated with side-effects that are observed with skin systemic psoralen with UVA (PUVA) therapy, since the psoralen is not ingested orally nor applied to the skin.² The side-effects are primarily related to fluid shifts and the need for a central catheter. Rare side-effects of ECP include nausea, photosensitivity, transient hypotension, flushing, tachycardia, congestive heart failure and thrombocytopenia.^1,2 Contraindications to the use of ECP are summarized in Table 3. Currently, ECP is available in over 200 treatment centers across the world treating numerous diseases.² The use of ECP by hospital, region and indication in Canada is summarized in Tables 1-2. Unfortunately, treatment access is limited in Canada and significant knowledge gaps are recognized (i.e., paucity of randomized clinical trials and real-world evidence) amongst physicians and patients. As a result, this treatment may be significantly underused in Canada.

Table 3. Summary of contraindications to the use of ECP

CTCL

CTCL represents a group of lymphoproliferative disorders where there is an accumulation of malignant T-cell clones in the skin.² The most commonly recognized forms of CTCL are mycosis fungoides (MF) and SS. There are currently no curative treatments for CTCL, except for allo-transplantation which has been successful in select patients.² ECP is often used as a first-line treatment for SS, as well as for patients with erythrodermic MF or advanced CTCL.¹ Its use in early stages of CTCL remains controversial and impractical in Canada as many other effective treatment modalities are available (Table 4).^5,6 ECP can be used as monotherapy or it can be safely given in combination with phototherapy (narrow band or broadband UVB), radiotherapy, total skin electron beam (TSEB), systemic retinoids, interferons, anti-CCR4 monoclonal antibodies, histone deacetylase inhibitors, methotrexate, and/or other treatments.^1,2 One meta-analysis of 400 patients with all stages of CTCL showed a combined overall response rate (ORR) of 56% both when ECP was used as monotherapy and in combination with other therapies.² The complete response (CR) rates were 15% and 18% for monotherapy and combination therapy, respectively.² However, the ORR and CR were 58% and 15%, respectively, in erythrodermic patients, and 43% and 10% in patients with SS.² The CR was defined as a complete resolution of clinical evidence of disease and for normalization of CD4/CD8 ratio for at least 1 month. The partial response (PR) was defined as greater than 25% but less than 100% decrease in lesions and no development of new lesions for at least 1 month. ORR was defined as a sum of PR and CR. Furthermore, the United Kingdom consensus statement analyzed 30 studies between 1987 to 2007 and determined that the mean ORR and CR rates were 63% (range 33-100%) and 20% (range 0-62%), respectively, with higher response rates observed in erythrodermic patients. Many factors can explain the variability in the results of these studies, such as patient selection bias, stage of the disease, ECP treatment schedule, prior treatments, and end-point definitions.² In addition, there is a significant amount of inter-subject variability in response rates to ECP and factors that predict treatment response, as summarized in Table 5.²

Table 4. Treatment options for CTCL (MF)

Table 5. Baseline parameters and predictors of response to ECP in the treatment of cutaneous T-cell lymphoma, as per the European Dermatology Forum.

Different countries have varying guidelines with respect to the use of ECP in CTCL. Most recently, the European Dermatology Forum (EDF) published new recommendations in 2020. They recommend considering ECP as first-line therapy in patients with MF clinical stages IIIA or IIIB (erythroderma), or MF/SS stages IVA1 or IVA2 (Tables 6-7). Treatments are recommended every 2 weeks for the first 3 months, then every 3-4 weeks, with a treatment period of at least 6 months or until remission is achieved, followed by a maintenance period (Table 8).² ECP can take 3-6 months before a clinical response is appreciated, and therefore, no conclusions regarding its success should be drawn before that timeframe in erythrodermic patients.^1,2

Table 6. TNMB classification of MF and SS

Table 7. Clinical staging for MF and SS.

Table 8. ECP recommendations by cutaneous disease, as per the revised guidelines by the European Dermatology Forum in 2020.

GvHD

GvHD can be either acute or chronic based on clinical presentation and time to disease development.¹ Classic acute GvHD (aGvHD) occurs within 100 days of the transplantation with typical features, whereas chronic GvHD (cGvHD) presents after 100 days. However, persistent, recurrent or lateonset aGvHD can occur after 100 days with typical features of aGvHD. If features of both aGvHD and cGvHD are present, it is considered an overlap syndrome.⁷ cGvHD occurs in 30- 50% of patients receiving an allogenic transplant, involves multiple systems and most commonly presents with mucosal, skin, gastrointestinal and liver involvement.² First-line therapy consists of systemic glucocorticosteroids with or without a calcineurin inhibitor. Second-line therapies include ruxolitinib, ECP, mycophenolate mofetil, mTOR inhibitors, methotrexate, calcineurin inhibitor. Second-line therapies include ruxolitinib, ECP, mycophenolate mofetil, mTOR inhibitors, methotrexate, imatinib, ibrutinib and rituximab.² Notably, phase III randomized clinical trials evaluating ruxolitinib versus best available therapy for steroid refractory or dependent cGvHD demonstrated superiority of this drug when compared to ECP and other agents (ORR 50% vs. 26%, p<0.001).⁸ The average response rate to ECP is approximately 60% and studies have shown ORR rates ranging from 36-83%. In addition, CR in the skin, oral disease, and liver ranged from 31-93%, 21-100% and 0-84%, respectively.² Best responses using ECP are seen in skin followed by gastrointestinal and then hepatic GvHD. The EDF recommends considering ECP as an additional secondline therapy in patients with cGvHD that is steroid-dependent, steroid-intolerant, or steroid-resistant, as well as for those with recurrent infections or with a high-risk of relapse (Table 8). Also, steroid-dependent patients (i.e., inability to reduce corticosteroid dose to <0.5 mg/kg/day without recurrence of Grade II or worse cGvHD) could benefit from ECP.

Similarly, systemic glucocorticoids are currently used as firstline therapy for aGvHD.² However, response rates are <50%.² In 2019, the US FDA approved ruxolitinib for steroid-refractory aGVHD in adult and pediatric patients ≥12 years of age. This approval was based on an open-label, single-arm, multicenter study of ruxolitinib that enrolled 49 patients with steroidrefractory aGVHD Grades II-IV occurring after allogeneic hematopoietic stem cell transplantation.⁹ Clinical trials have shown the superiority of ruxolitinib therapy when compared to ECP and other treatments (ORR 62% vs. 39%, p<0.001).¹⁰ In these patients, ECP may serve as an additional second-line treatment with ORR of 65-100% in the skin, 0-100% in the liver, and 40-100% in the gastrointestinal tract.² As such, the EDF recommends adjunct ECP, as second-line therapy, in patients not responding to appropriate doses of systemic corticosteroids (Table 8). Interestingly, it is also showing promising results as a prophylaxis therapy to prevent cGvHD.¹ This treatment option may be considered by dermatologists consulting on these patients in acute setting in the hospital especially at times when the diagnosis is uncertain, as ECP is recognized as not being an immunosuppressive therapy.

SSc

SSc is a multisystemic connective tissue disease characterized by collagen deposits in the skin and other visceral organs.^1,11 Although there are currently no FDA-approved treatments for cutaneous involvement in SSc, limited studies have investigated the use of ECP and have shown promising results.¹¹ For example, one multicenter trial showed that ECP was well-tolerated and improved disease severity, the mean percentage of skin involvement (-7.7% from baseline after 10 months, p=0.01) and the mean oral aperture measurements (+2.1 mm from baseline after 10 months, p=0.02).^11,12 Other studies have shown that ECP leads to improvement in dermal edema and skin elasticity, normalization of collagen synthesis, and improvement of extracutaneous symptoms, and that ECP-treated patients with SSc have a favorable long-term survival.^1,13 Further, one study found that, in most patients, ECP leads to a reduced usage of corticosteroids and other immunosuppressive agents, which have numerous adverse effects.¹⁴ The EDF currently recommends ECP as second-line or adjuvant therapy for SSc, either as monotherapy or in combination with other treatments (Table 8).¹¹

Other Cutaneous Conditions

ECP has been studied in numerous other cutaneous diseases, including atopic dermatitis (AD), immunobullous diseases, eosinophilic fasciitis and others. Although there are many other treatment options for AD, including emollients, topical therapies, phototherapy/photochemotherapy, immunosuppressive medications, targeted therapies¹⁵ and monoclonal antibodies, several small open-label trials have shown that ECP is beneficial in patients with severe AD, including erythrodermic AD, that are not responding to standard therapy. Although previous guidelines have not recommended routinely treating AD with ECP given the lack of consistent findings and the multiple other treatment options available, the EDF’s revised guidelines recommend its use as second-line therapy in patients that meet specific criteria (Table 8).¹¹ However, as new effective treatments are emerging for the treatment of AD, ECP should only be reserved for exceptional patients. Studies have also shown promising results for the use of ECP in pemphigus. One study of 11 patients with severe treatment-resistant pemphigus vulgaris or foliaceus showed an OR rate of 91% and CR rate of 73%.¹¹ As such, the EDF recommends ECP in patients with pemphigus vulgaris or foliaceus that is recalcitrant to conventional first- and second-line therapies.¹¹ Further, the EDF recommends considering ECP for severe epidermolysis bullosa acquisita (EBA) and erosive oral lichen planus that is refractory to conventional topical and/or systemic therapies.¹¹ Low level evidence suggests a possible role for ECP in the treatment of lupus erythematosus, however, further controlled clinical trials are needed to assess its efficacy. For this reason, no official recommendations for the use of ECP in lupus erythematosus have been published to date.¹¹ Studies have also investigated the use of ECP in other cutaneous diseases, including psoriasis, nephrogenic fibrosing dermopathy, morphea and scleromyxedema, however, the results have been inconclusive.¹¹

Pediatric Population

Many studies support the use of ECP in a pediatric population. It has been used as an off-label treatment for various conditions, including aGvHD and cGvHD.¹¹ In this patient population, the ECP protocol is adapted and can vary depending on the patient’s weight. Importantly, very few side effects are reported in this population, which further supports the favorable safety profile of ECP.¹¹

Conclusion

In conclusion, ECP has been used on- and off-label for decades to treat numerous diseases, including SS, CTCL, GvHD, and SSc, among others. Results from multiple studies have shown promising response rates, and ECP has an overall excellent safety profile with very few adverse events reported.^2,11 Unlike many other immunomodulatory therapies, an increased risk of infection has not been observed with ECP, which can be a significant cause of morbidity and mortality for patients on other immunosuppressive therapies.¹¹ Although ECP is still being studied for multiple diseases, in Canada clinicians should restrict its use to the diseases that have been extensively studied, as per the EDF guidelines.

Funding: The genesis of the paper was initiated at a meeting organized by a pharmaceutical company (Mallinckrodt Inc.) and EN, IT, WG, JD, MK, RG, CL and IVL were provided honoraria to attend that meeting. No funding bodies or other organizations had any role in data collection and analysis, decision to publish, or preparation of the manuscript.

Acknowledgment: We thank RBC Consultants for editorial support, facilitating the preparation of tables, and coordinating the review of the manuscript.

Purchase Article PDF for $1.99

¹Skin Centre for Dermatology, Peterborough, ON and Queen’s University, Kingston, ON, Canada
²Associate Professor, University of Toronto, ON, Canada
³Lynde Institute for Dermatology, Markham, ON, Canada
⁴Clinical Instructor, Department of Dermatology and Skin Science, University of British Columbia, Vancouver, BC, Canada
⁵Assistant Professor in Clinical Teaching faculty of medicine, Sherbrooke University, Sherbrooke, QC, Canada
⁶Assistant Professor, Division of Dermatology, University of Ottawa, Ottawa, ON, Canada
⁷Dermatology, CHU de Québec-Université Laval, Quebéc, QC, Canada
⁸Centre hospitalier universitaire Dr-Georges-L.-Dumont, Moncton, NB, Canada
⁹Assistant Professor, Department of Internal Medicine, University of Manitoba, Winnipeg, MB, Canada
¹⁰Queen’s University, Kingston, ON, Canada
¹¹Clinical Associate Professor, Memorial University of Newfoundland, St. John’s, NL, Canada
¹²Clinical Assistant Professor, Discipline of Medicine, Memorial University of Newfoundland, St. John’s, NL, Canada
¹³Associate Clinical Professor Dermatology, University of Calgary, AB, Canada
¹⁴Associate Professor, Dalhousie University, Halifax, NS, Canada
¹⁵Université de Montréal, Montréal and Dermatologie Sima Recherches, Verdun, QC, Canada
¹⁶Dermatology, CHU de Québec-Université Laval, Québec, QC, Canada
¹⁷Ottawa, ON, Canada
¹⁸Sunnybrook Health Sciences Centre and University of Toronto, Toronto, ON, Canada
¹⁹Division of Dermatology, Department of Medicine, University of Calgary, Calgary, AB, Canada

Introduction

Chronic hand dermatitis (CHD) can affect up to 10% of the population and have a significant impact on quality of life (QoL).^1-3 It presents as a chronic, recurrent, inflammatory condition with erythema, scaling, fissuring, pruritus and lichenification of the hands. The etiology is multi-factorial and includes both genetic and environmental factors.¹Treatment is notoriously difficult as symptoms frequently recur despite standard therapy. Undertreated CHD can lead to a substantial burden on patients as well as an economic burden on society due to reduced work productivity and many work-related compensation claims.^2-5

Recently, practical guidelines for the management of CHD were published in the Skin Therapy Letter, Family Practice Edition (October 2016).⁶ This series of cases using alitretinoin (Toctino®, GlaxoSmithKline and distributed by Actelion, Laval, QC) is a follow on to that publication to put the guidelines into context.

Abbreviations: AEs – adverse events, CHD – chronic hand dermatitis, ENT – ear, nose, and throat, HD – hand dermatitis, QoL – quality of life

Diagnosing HD – Important points to cover

• Determine if the patient has eczema, or a childhood history of eczema (erythematous, scaling patches with some fissuring in typical locations).
• Ask about a personal or family history of atopy, including asthma, seasonal ENT allergies, nasal polyps.
• Ask about a history of psoriasis and comorbidities such as psoriatic arthritis.
• Does the patient have occupational exposures that could lead to allergic or irritant contact dermatitis?
• Has the patient had any recent exposures to irritants? Frequent handwashing?
• Do a skin scraping for fungal KOH and culture to rule out tinea manuum, as needed.

Case

Case 1:

A 39-year old dairy farmer presented with a 15-year history of redness, scaling and painful fissuring of the hands. He has used multiple potent topical steroids over the years with only temporary benefit. Despite the continued use of topical steroids he reported that his symptoms always return. After a skin scraping for fungal culture was taken and reported negative, he was referred to a dermatologist for assessment.

A diagnosis of CHD was confirmed. Given the failure of potent topical steroids for >8 weeks and inability to attend regular phototherapy sessions, his dermatologist started him on alitretinoin 30 mg PO QD for a 6-month course. By week 12, his hands were almost clear and by week 24, his hands were clear. He stopped the medication after a 6-month course of alitretinoin and entered into remission. At follow up appointments at year 5 and year 11, his hands remained clear. (Figure 1 and 2)

• Alitretinoin (9-cis retinoic acid) is an endogenous retinoid (physiological vitamin A derivative) and is the only systemic agent approved for CHD. It has proven to be safe and effective for the treatment of CHD in controlled clinical trials7-10 and in real-world experience.^11-15
• In the pivotal BACH trial, 1032 patients with CHD were treated with alitretinoin (10 mg, 30 mg) or placebo for up to 24 weeks. The group that received alitretinoin 30 mg QD had up to a 75% median reduction in signs and symptoms and 48% were clear or almost clear at the week 24 time point.⁸
• In patients who were clear/almost clear, 67% did not relapse within 24 weeks off therapy. In those patients who did relapse, 80% of those re-treated with 30 mg QD recaptured their response.⁹
• Approximately half of those patients receiving 10 mg QD and 40% of those receiving 30 mg QD who did not initially respond to alitretinoin, did respond to retreatment with the 30 mg QD dose for an additional 24 weeks.¹⁰
• The majority of patients do not require long-term management with alitretinoin as some patients enter a remission period with 24 weeks of therapy. For those who relapse and require re-treatment, the majority recapture their response⁹ and in those patients who require ongoing therapy, there are no safety concerns with continuous dosing.^10,12,13

Figure 2. No further prescribed systemic or topical treatments since 2005. (2A) Year 5, (2B) Year 11.Photos courtesy of Dr. Yves Poulin

Case 2:

A 52-year old female teacher presented with a 15-year history of recurrent CHD. She had tried numerous moisturizers and mild to superpotent topical steroids over the years without relief. She tried 6 months of narrowband UVB phototherapy with only partial resolution. She was frustrated and looking for a better solution. Her past medical history is significant for obesity and hypothyroidism. Her dermatologist started her on alitretinoin 30 mg PO QD with excellent response. However, her baseline liver enzymes were 1.5 times the upper limit of normal and 2 months after initiating therapy, increased to 3 times the upper limit so the alitretinoin was discontinued.

Ultrasound demonstrated fatty liver and further work up revealed diabetes. After initiation of metformin and 10 kg of weight loss, the patient’s transaminases returned to within the normal range but her CHD flared. A repeat course of phototherapy and superpotent topical steroids failed again. Slow re-introduction of alitretinoin at 10 mg, followed by 20 mg and then 30 mg led to recapture of response and her transaminases have remained within normal range throughout a continued 3-year course of therapy with alitretinoin.

• In clinical trials, alitretinoin was well tolerated by the majority of patients, although a dose dependent effect was noted with the AE of headache (up to 21.6% with 30 mg dose, 11.6% with 10 mg dose) and with mucocutaneous side effects.^8-10
• Laboratory abnormalities consistent with a retinoid class effect were noted in the trials, with dose dependent elevations in serum cholesterol and triglycerides most commonly noted; reduced thyroid stimulating hormone was reported, but there were no cases of clinical hypothyroidism.^8-10
• A hepatic effect of alitretinoin was not identified in the clinical trials^8-10 or in real-world studies,^11,14 however transient and reversible increases in transaminases have been noted in the product monograph.¹⁶ In the case presented, her transaminitis was likely related to her underlying fatty liver; she had no further issues with ongoing alitretinoin use, once she had proper management of her comorbid conditions (obesity, diabetes). If persistent elevations in transaminases are noted, reduction of the dose or discontinuation should be considered.¹⁶
• Post-marketing surveillance of the use of alitretinoin has identified AEs of special interest in the retinoid class that were not identified in clinical trials. Depression has been reported as well as very rare cases of inflammatory bowel disease and benign intracranial hypertension.¹⁴
• Work-up and monitoring for patients taking alitretinoin is similar to other commonly used retinoids (isotretinoin, acitretin) and should include: baseline hepatic transaminases and lipid profiles, repeated at one month, and then every 2-3 months during therapy. Beta-HCG should be done in women of child-bearing potential prior to initiation of therapy and repeated monthly during therapy and one month after discontinuation.¹⁶
• Retinoids are potent teratogens so practitioners should follow the Pregnancy Prevention Program,¹⁶ and women of child-bearing potential should be counselled on strict pregnancy prevention, use of two highly effective forms of birth control simultaneously and be monitored monthly with a serum pregnancy test.¹⁶
• Of 2 pregnancies reported in the clinical trials and 12 in post-marketing reports, 13 pregnancies were terminated early (elective or spontaneous abortion) and one healthy baby was born. No congenital abnormalities have been reported to date.¹⁴

Case 3:

A 68-year old retired woman had been suffering from hand dermatitis for the past 3 years since she had been at home caring for her elderly husband. She had been applying emollients throughout the day and trying to avoid frequent hand washing. Neither the potent topical corticosteroid nor the topical calcineurin inhibitor prescribed for her have helped. She was finding chores at home difficult with fissured finger tips and could not enjoy her hobbies of knitting or gardening because of the painful fissures. She was started on alitretinoin at 30 mg PO QD and noted good response, however she suffered from frequent headaches. Her dose was reduced to 10 mg PO QD with partial return of her CHD symptoms. Addition of a potent topical steroid and a course of narrowband UVB phototherapy to the alitretinoin 10 mg QD provided an effective combination regimen to control her CHD.

• Although clinical trials excluded concomitant therapy with topical medications or phototherapy, these concomitant treatments are often continued or added in real-world practice.^11,13
• Narrowband UVB phototherapy has been shown to be effective in CHD.¹⁷
• We know from vast experience in treating psoriasis, the combination of retinoids and UVB phototherapy is a very safe and effective way to optimize treatment outcomes and can reduce the cumulative dose of UVB exposure.^18,19
• According to expert opinion based on the experiences of the authors, combination of alitretinoin with topical corticosteroids or phototherapy is safe, can improve responses and may be a good option for patients who can only tolerate the 10 mg QD dose or who have not reached clear/almost clear status with the 30 mg QD dose.¹³
• Regardless of the combination of treatments selected, always remember to assess adherence and counsel each patient on appropriate prevention and avoidance strategies, regular moisturization and proper use of medications.⁶ (see Figure 3)

Case 4:

A 34-year-old mechanic presented with a 3.5-year history of CHD. His job is dependent on the use of his hands and he has a young family to support. He responded poorly to multiple courses of mid to superpotent topical steroids and a topical calcineurin inhibitor. Contact dermatitis was suspected and he was referred to a dermatologist for patch testing.

Patch testing with the North American Contact Dermatitis Group standard series revealed a positive reaction to methylisothiazolinone, which happened to be an ingredient in the citrus hand scrub he used at work and in the wet wipes he used when changing his child’s diaper. Modification of his home and work place environment to avoid this allergen has improved his CHD somewhat but it is not clear and is still causing problems at work. He was fearful of jeopardizing his employment and requested further treatment. A course of alitretinoin at 30 mg QD was initiated with good response and he continued to avoid methylisothiazolinone at work and home.

• CHD may be related to a contact dermatitis, which can be either irritant contact dermatitis or in some cases allergic contact dermatitis.²⁰ Many times patients also have an underlying atopic diathesis putting them at increased risk of developing hand dermatitis.²¹
• Contact dermatitis should be suspected when patients are not responding to treatment or worsening despite therapy; these patients should be referred for patch testing.^20,21
• Many different allergens can be responsible for the onset or exacerbation of CHD. In this particular patient’s case, methylisothizolinene, a common preservative in personal care products,^21-23 was a factor. This outlines the importance of patch testing, and considering contact dermatitis in the differential diagnosis.
• Whether the patient has CHD of unknown etiology or due to irritant contact dermatitis, allergic contact dermatitis or underlying atopic dermatitis, alitretinoin is still an option for management as second line therapy after failure of potent or superpotent topical steroids. Patch testing can help determine if an allergen should be avoided as part of the management plan, although lengthy wait times for this test in some jurisdictions should not delay therapy. In some cases, once identified, allergen avoidance may be all that is necessary for symptom resolution.
• In the real-world observational study, PASSION, it was shown that treating CHD with alitretinoin resulted in significant and rapid improvement in symptoms, increased QoL and reduced work impairment. The number of patients rated as ‘disabled’ was reduced from 12.4% at baseline to 2.2% at week 24, and those reporting no work impairment increased from 2.7% at baseline to 63.7% at week 24, showing that alitretinoin can significantly reduce work incapacity.¹⁵

Conclusions

CHD is a common condition causing a significant impact on quality of life and an economic burden due to reduced productivity and cause for disability. Many patients do not respond to standard treatments, making it a challenging condition to manage. This case series is a follow on to a recent publication of practical guidelines for the general practitioner on the management of CHD, to put the use of alitretinoin in context. The addition of alitretinoin to our therapeutic armamentarium has changed the way we are able to manage patients who suffer from this condition, providing a safe and effective treatment option to improve QoL and reduce work impairment. When managing patients with CHD, we must always remember to confirm the diagnosis, assess adherence, counsel our patients on prevention and avoidance strategies, encourage moisturization and proper use of medications and refer patients for patch testing if a contact allergy is suspected.

Patient Resources:
https://eczemahelp.ca/
http://www.eczemacanada.ca/

Acknowledgement

The authors wish to acknowledge Evert Tuyp, MD, FRCPC for his editorial assistance in the preparation of this manuscript.

References

1. Thyssen JP, et al. Contact Dermatitis. 2010 Feb;62(2):75-87.
2. Lynde C, et al. J Cutan Med Surg. 2010 Nov-Dec;14(6):267-84.
3. Kouris A, et al. Contact Dermatitis. 2015 Jun;72(6):367-70.
4. Augustin M, et al. Br J Dermatol. 2011 Oct;165(4):845-51.
5. Cvetkovski R, et al. Br J Dermatol. 2005;152(1):93-8.
6. Gooderham M, et al. Skin Therapy Letter, Family Practice Edition. 2016 Oct;11(1):1-5.
7. Ruzicka T, et al. Arch Dermatol. 2004 Dec;140(12):1453-9.
8. Ruzicka T, et al. Br J Dermatol. 2008 Apr;158(4):808-17.
9. Bissonnette R, et al. Br J Dermatol. 2009 Feb;162(2) :420-6.
10. Lynde C, et al. Clin Exp Dermatol. 2012 Oct;37(7):712-7.
11. Diepgen TL, et al. Acta Derm Venereol. 2012 May;92(3)251-5.
12. Gulliver WP, et al. J Cutan Med Surg. 2012 May;92(3):251-5.
13. Ham K, et al. J Cutan Med Surg. 2014 Oct;18(5):332-6.
14. Morris M, et al. J Dermatolog Treat. 2016;27(1):54-8
15. Thaçi D, et al. J Dermatolog Treat. 2016 Nov;27(6):577-83.
16. Toctino® (alitretinoin) soft capsules (product monograph on the Internet). Mississauga (ON): GlaxoSmithKline Inc, Distributed by Actelion Pharmaceuticals Canada, 2016 [revised 04 APR 2016].
17. Sezer E, Etikan I. Photodermatol Photoimmunol Photomed. 2007 Feb;23(1):10-4.
18. Green C, et al. Br J Dermatol. 1992 Jul;127(1):5-9.
19. Ruzicka T, et al. Arch Dermatol. 1990 Apr;126(4):482-6.
20. Diepgen TL, et al. JDDG. 2015 Jan;13(1):77-85.
21. Mowad C, et al. J Am Acad Dermatol. 2016 Jun;74(6):1029-40.
22. Ham K, et al. Dermatitis. 2015 Jul-Aug;26(4):166-9.
23. Cahill JL, et al. Med J Australia. 2014 Mar;200(4):208

¹Department of Dermatology and Skin Science, University of British Columbia, Vancouver, BC, Canada
²Division of Dermatology, St. Paul’s Hospital, Vancouver, BC, Canada

ABSTRACT

Parabens are preservatives used in a variety of personal care, cosmetic, pharmaceutical and food products. Studies have confirmed the ubiquitous presence of parabens, with levels detected in wastewater, rivers, soil and house dust. Parabens have also been detected in human tissues and bodily fluids, but it is the discovery of these chemical compounds in the breast tissue of patients with breast cancer that has raised public concern over their use. It is hypothesized that the estrogenic properties of parabens may play a role in breast cancer development. However, studies investigating the health effects of parabens are conflicting. At this point, there is an insufficient amount of data suggesting serious consequences from paraben use and exposure to warrant drastic avoidance measures or government regulations.

Key Words:
parabens, preservatives, cosmetic products, breast cancer, spermatotoxicity, regulations, environment

Introduction

Parabens are preservatives that are used in a wide range of cosmetic, pharmaceutical and some food products. Parabens are esters of para-hydroxybenzoic acid and commonly include methylparaben, ethylparaben, propylparaben and butylparaben.¹ The recent health concerns regarding parabens stem from a study published in 2004 that detected parabens in breast tissue from patients with breast cancer.² Public pressure has persuaded several governments to introduce regulations on the use of parabens in consumer products. In this review, we examine the data regarding the health effects of parabens to provide physicians and patients with a better understanding of this issue.

Consumer Products and Parabens

Parabens have been used in food, cosmetic and pharmaceutical products since the 1930s. Their use in cosmetic consumer products is more prevalent than their utility elsewhere. Products found to contain parabens include hand soap, body lotion, shampoo, conditioner, face lotion, facial cleansers, foundation, lipstick, mascara, hair spray/mousse/gel, toothpaste and sunscreen.^1,3,4 One study identified parabens in 44% of cosmetics tested.³ In personal care products tested in the US, concentrations of methylparaben up to 1.0% were found, with lipsticks containing the highest concentration ranging from 0.15% to 1.0%.¹ The other parabens are used at concentrations lower than methylparaben in personal care products. Methylparaben and propylparaben are the most commonly used parabens in pharmaceutical products at concentrations of up to 20%;¹ both of these preservatives are also used in food products such as jams, jellies, fillings and toppings at concentrations of up to 0.1%.^1,5

Parabens in the Environment

Parabens have been found in urban streams into which treated or untreated effluent from wastewater treatment plants flows.^6,7 Consequently, these chemical compounds have been identified in rivers and drinking water sources.^6,8 Parabens have been detected in soil from agricultural fields, possibly from irrigation or fertilization practices.^9,10 The dust in houses has also been found to contain parabens.^11,12 Although commercially used parabens are of synthetic origin, some parabens are produced by living organisms, specifically by plants and microbes, e.g., a marine bacterial strain belonging to the genus Microbulbifer.¹³ Plants such as blueberries, carrots, olives, strawberries and others produce parabens (mainly methylparaben) for its presumed antimicrobial activity.^14-16 Overall, the concentrations of parabens within the environment are low with water concentrations around 7 ng/L and effluent concentrations up to 6 µg/L, soil concentrations range from 0.5 to 8 ng/g while house dust contained up to 2400 ng/g.7-11

Parabens in the Human Body

Parabens can enter the human body through the skin and parenterally. The average daily total personal paraben exposure is estimated to be 76 mg, with cosmetics and personal care products accounting for 50 mg, 25 mg from pharmaceutical products, and 1 mg from food.^17-19 Parabens applied to the skin are metabolized by keratinocyte carboxylesterases and the conjugated metabolites are excreted in urine and bile.^20,21 Oral or intravenous parabens are metabolized by esterases within the intestine and liver.¹ Parabens have been detected in urine, serum, breast milk and seminal fluid, but most worrisome has been the detection in breast tissue from patients with breast cancer.^2,22-26 Some have hypothesized that the higher concentration in the upper lateral breast near the axilla correlates with exposure from underarm deodorant and an increased incidence of breast cancer development in the area.^27,28 Still absolute concentrations indicate that levels of paraben within human fluids and tissue are low with average urine concentrations reported in the US ranging from 0.5 to 680 ng/mL and breast tissue concentrations ranging from 0 to 5100 ng/g of breast tissue (the median being 85.5 ng/g).^25,26 These low concentrations should be interpreted in the context of known estrogenic effects of parabens, which are discussed in the next section.

Toxicity and Adverse Effects of Parabens

Human and animal studies have failed to show that parabens have any acute toxicity by various routes of administration. As such, many of the studies examining paraben toxicity have focused on the long-term effects of chronic exposure.

The estrogenic activity of parabens was first identified in 1998 and has since been validated in vitro and in vivo.^1,29,30 Parabens bind human estrogen receptors, although with affinities 10,000 to 1,000,000 times less than estradiol.^29,31 Butylparaben and propylparaben have higher estrogenic activity than methylparaben or ethylparaben, but butylparaben and propylparaben are detected at concentrations 10 to 1000 times less than methylparaben in humans.³² The estrogenic effects in vivo have been demonstrated by uterotrophic (uterine growth) assays in mice and rats.^1,33 However, this effect did not prevent implantation of a fertilized egg, which is considered the most sensitive measure of estrogen toxicity.^33,34 As mentioned, it has been hypothesized that the estrogenic activity of parabens may promote breast cancer development. The concentration of estradiol in normal human breast tissue is 55.3 pg/g, suggesting there is a safety margin of 10 to 1000 times for parabens to approximate normal estradiol activity.^1,25,32 The paraben breast cancer data shows no or low parabens in a subset of patients and there are no comparisons with normal controls.^2,25 Hence, having not established a clear correlation, it is difficult to put forth a causal relationship between parabens and breast cancer development.

Another major area of study has been the effect of parabens on the male reproductive system, but findings are conflicting.³⁵ One in vitro study found that human sperm were not viable when exposed to parabens at concentrations of 1 mg/mL.³⁶ In vivo studies in mice did not replicate this result, with no spermatotoxic effects at paraben concentrations of 1%.³⁷ Conflicting results have also been reported in rats, with one study showing decreased sperm number and activity while another study found no adverse reproductive effects.^35,38 In humans, men with fertility problems including low sperm count and decreased motility were assayed for paraben exposure by measuring urine paraben levels.²³ No correlation between sperm count or motility and parabens levels was found.

Parabens, as is the case for many preservatives, can be allergenic in a small subset of the population. This sensitization commonly manifests as an eczematous rash. The rates of reported sensitization to parabens range from 0.5% to 3.5%.¹⁷ These rates of sensitization are amongst the lowest of all preservatives.^17,18 In addition, there are reports of immediate immunoglobulin Emediated allergic reactions to parabens resulting in urticaria and, in one case, bronchospasm.^39,40 However, these immediate allergic reactions are extremely rare.

Government and Regulatory Control of Parabens

Government regulatory boards have examined parabens and most have agreed that current concentrations of parabens are safe for consumer use. The European Union (EU) has set up limits on paraben use that have also been reviewed by the European Scientific Committee on Consumer Products (SCCP). In 2006, the SCCP concluded that parabens can be safely used in cosmetic products at concentrations of 0.4% for any individual paraben and 0.8% for total paraben concentrations.^1,41 These limits echo the legislative limits put in place by the EU. The Danish government went further in 2011 by banning the use of parabens in personal care products intended for children younger than 3 years of age. This decision is based on the possibility of high systemic absorption from an immature metabolism and skin barrier dysfunction.⁴² In the United States, the Cosmetic Ingredient Review (CIR) assesses ingredients for safety and is reviewed by the US Food and Drug Administration (FDA). The CIR has recommended the same maximum paraben concentrations as suggested by the SCCP and as legislated by the EU.¹ However, it should be noted that the CIR recommendations are only guidelines and manufacturers are not required to follow them. Likewise in Canada, there are no laws regulating paraben concentrations, but Health Canada agrees with the FDA and the CIR in regards to the safety of parabens and the adoption of maximum concentration guidelines.⁴³

Alternatives to Parabens

There are numerous preservatives that could be used in place of parabens. Some other commonly used preservatives include formaldehyde, quaternium-15, imidazolidinyl urea, diazolidinyl urea and dimethyloldimethyl hydantoin.¹⁸ These preservatives more commonly cause allergic reactions and some pose more serious health implications, such as formaldehyde and its causal link with cancer.¹⁸ The use of “natural” preservatives has been advocated, including grapefruit seed extract (GSE).⁴⁴ Unfortunately, GSE can interact with medications due to its ability to inhibit CYP3A4, an important enzyme involved in drug metabolism.⁴⁵ Other natural preservatives include thymol, cinnamaldehyde, allyl isothiocyanate, citric acid, ascorbic acid and rosemary extract.^46,47 These natural preservatives inhibit microbial growth in vitro, but the few studies testing antimicrobial activity in food products have provided equivocal results.^46,48,49 Therefore, further studies to determine their efficacy, safety and toxicology are warranted before widespread use.

Conclusion

The expectation of long shelf lives and microorganism-free consumer products mandates the use of preservatives. Ideally, preservatives should be active at low concentrations against a wide variety of microorganisms without interfering with other ingredients in the product, while also remaining nontoxic to humans and available at low cost to manufacturers. Parabens have been used for over 80 years and, despite reports of adverse reactions, they have proven to be amongst the safest and most well tolerated preservatives. Although the possible association of parabens with decreased sperm quality and breast cancer does warrant continued examination, the current data does not support drastic regulations or personal restrictions to exposure. Other recently regulated chemicals, such as phthalates and bisphenol A, may serve as archetypes for continued vigilance and investigation.^50,51

References

1. Cosmetic Ingredient Review Expert Panel. Final amended report on the safety assessment of Methylparaben, Ethylparaben, Propylparaben, Isopropylparaben, Butylparaben, Isobutylparaben, and Benzylparaben as used in cosmetic products. Int J Toxicol. 2008;27(Suppl 4):1-82.
2. Darbre PD, Aljarrah A, Miller WR, et al. Concentrations of parabens in human breast tumours. J Appl Toxicol. 2004 Jan;24(1):5-13.
3. Yazar K, Johnsson S, Lind ML, et al. Preservatives and fragrances in selected consumer-available cosmetics and detergents. Contact Dermatitis. 2011 May;64(5):265-72.
4. Witorsch RJ, Thomas JA. Personal care products and endocrine disruption: A critical review of the literature. Crit Rev Toxicol. 2010 Nov;40(Suppl 3):1-30.
5. Wang L, Zhang X, Wang Y, et al. Simultaneous determination of preservatives in soft drinks, yogurts and sauces by a novel solid-phase extraction element and thermal desorption-gas chromatography. Anal Chim Acta. 2006 Sep;577(1):62-7.
6. Yamamoto H, Tamura I, Hirata Y, et al. Aquatic toxicity and ecological risk assessment of seven parabens: individual and additive approach. Sci Total Environ. 2011 Dec;410-411:102-11.
7. Gonzalez-Marino I, Quintana JB, Rodriguez I, et al. Simultaneous determination of parabens, triclosan and triclocarban in water by liquid chromatography/ electrospray ionisation tandem mass spectrometry. Rapid Commun Mass Spectrom. 2009 Jun;23(12):1756-66.
8. Pedrouzo M, Borrull F, Marce RM, et al. Ultra-high-performance liquid chromatography-tandem mass spectrometry for determining the presence of eleven personal care products in surface and wastewaters. J Chromatogr A. 2009 Oct;1216(42):6994-7000.
9. Ferreira AM, Moder M, Laespada ME. Stir bar sorptive extraction of parabens, triclosan and methyl triclosan from soil, sediment and sludge with in situ derivatization and determination by gas chromatography-mass spectrometry. J Chromatogr A. 2011 Jun;1218(25):3837-44.
10. Perez RA, Albero B, Miguel E, et al. Determination of parabens and endocrinedisrupting alkylphenols in soil by gas chromatography-mass spectrometry following matrix solid-phase dispersion or in-column microwave-assisted extraction: a comparative study. Anal Bioanal Chem. 2012 Mar;402(7): 2347-57.
11. Ramirez N, Marce RM, Borrull F. Determination of parabens in house dust by pressurised hot water extraction followed by stir bar sorptive extraction and thermal desorption-gas chromatography-mass spectrometry. J Chromatogr A. 2011 Sep;1218(37):6226-31.
12. Wang L, Liao C, Liu F, et al. Occurrence and human exposure of p-hydroxybenzoic acid esters (parabens), bisphenol A diglycidyl ether (BADGE), and their hydrolysis products in indoor dust from the United States and three East Asian countries. Environ Sci Technol. 2012 Nov 6;46(21):11584-93.
13. Peng X, Adachi K, Chen C, et al. Discovery of a marine bacterium producing 4-hydroxybenzoate and its alkyl esters, parabens. Appl Environ Microbiol. 2006 Aug;72(8):5556-61.
14. Kang YH, Parker CC, Smith AC, et al. Characterization and distribution of phenolics in carrot cell walls. J Agric Food Chem. 2008 Sep;56(18):8558-64.
15. Sellappan S, Akoh CC, Krewer G. Phenolic compounds and antioxidant capacity of Georgia-grown blueberries and blackberries. J Agric Food Chem. 2002 Apr;50(8):2432-8.
16. Huang WY, Zhang HC, Liu WX, et al. Survey of antioxidant capacity and phenolic composition of blueberry, blackberry, and strawberry in Nanjing. J Zhejiang Univ Sci B. 2012 Feb;13(2):94-102.
17. Cashman AL, Warshaw EM. Parabens: a review of epidemiology, structure, allergenicity, and hormonal properties. Dermatitis. 2005 Jun;16(2):57-66.
18. Sasseville D. Hypersensitivity to preservatives. Dermatol Ther. 2004;17(3): 251-63.
19. Soni MG, Carabin IG, Burdock GA. Safety assessment of esters of p-hydroxybenzoic acid (parabens). Food Chem Toxicol. 2005 Jul;43(7): 985-1015.
20. Darbre PD, Harvey PW. Paraben esters: review of recent studies of endocrine toxicity, absorption, esterase and human exposure, and discussion of potential human health risks. J Appl Toxicol. 2008 Jul;28(5):561-78.
21. Pedersen S, Marra F, Nicoli S, et al. In vitro skin permeation and retention of parabens from cosmetic formulations. Int J Cosmet Sci. 2007 Oct;29(5):361-7.
22. Frederiksen H, Jorgensen N, Andersson AM. Parabens in urine, serum and seminal plasma from healthy Danish men determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS). J Expo Sci Environ Epidemiol. 2011 May;21(3):262-71.
23. Meeker JD, Yang T, Ye X, et al. Urinary concentrations of parabens and serum hormone levels, semen quality parameters, and sperm DNA damage. Environ Health Perspect. 2011 Feb;119(2):252-7.
24. Ye X, Bishop AM, Needham LL, et al. Automated on-line column-switching HPLC-MS/MS method with peak focusing for measuring parabens, triclosan, and other environmental phenols in human milk. Anal Chim Acta. 2008 Aug;622(1-2):150-6.
25. Barr L, Metaxas G, Harbach CA, et al. Measurement of paraben concentrations in human breast tissue at serial locations across the breast from axilla to sternum. J Appl Toxicol. 2012 Mar;32(3):219-32.
26. Calafat AM, Ye X, Wong LY, et al. Urinary concentrations of four parabens in the U.S. population: NHANES 2005-2006. Environ Health Perspect. 2010 May;118(5):679-85.
27. Darbre PD. Environmental oestrogens, cosmetics and breast cancer. Best Pract Res Clin Endocrinol Metab. 2006 Mar;20(1):121-43.
28. Harvey PW. Parabens, oestrogenicity, underarm cosmetics and breast cancer: a perspective on a hypothesis. J Appl Toxicol. 2003 Sep;23(5):285-8.
29. Routledge EJ, Parker J, Odum J, et al. Some alkyl hydroxy benzoate preservatives (parabens) are estrogenic. Toxicol Appl Pharmacol. 1998 Nov;153(1):12-9.
30. Harvey PW, Darbre P. Endocrine disrupters and human health: could oestrogenic chemicals in body care cosmetics adversely affect breast cancer incidence in women? J Appl Toxicol. 2004 May;24(3):167-76.
31. Blair RM, Fang H, Branham WS, et al. The estrogen receptor relative binding affinities of 188 natural and xenochemicals: structural diversity of ligands. Toxicol Sci. 2000 Mar;54(1):138-53.
32. Golden R, Gandy J, Vollmer G. A review of the endocrine activity of parabens and implications for potential risks to human health. Crit Rev Toxicol. 2005 Jun;35(5):435-58.
33. Shaw J, deCatanzaro D. Estrogenicity of parabens revisited: impact of parabens on early pregnancy and an uterotrophic assay in mice. Reprod Toxicol. 2009 Jul;28(1):26-31.
34. Daston GP. Developmental toxicity evaluation of butylparaben in Sprague- Dawley rats. Birth Defects Res B Dev Reprod Toxicol. 2004 Aug;71(4):296-302.
35. Kang KS, Che JH, Ryu DY, et al. Decreased sperm number and motile activity on the F1 offspring maternally exposed to butyl p-hydroxybenzoic acid (butyl paraben). J Vet Med Sci. 2002 Mar;64(3):227-35.
36. Song BL, Li HY, Peng DR. In vitro spermicidal activity of parabens against human spermatozoa. Contraception. 1989 Mar;39(3):331-5.
37. Oishi S. Effects of butyl paraben on the male reproductive system in mice. Arch Toxicol. 2002 Jul;76(7):423-9.
38. Oishi S. Lack of spermatotoxic effects of methyl and ethyl esters of p-hydroxybenzoic acid in rats. Food Chem Toxicol. 2004 Nov;42(11):1845-9.
39. Grzanka A, Misiolek H, Filipowska A, et al. Adverse effects of local anaesthetics – allergy, toxic reactions or hypersensitivity. Anestezjol Intens Ter. 2010 Oct;42(4):175-8.
40. Kajimoto Y, Rosenberg ME, Kytta J, et al. Anaphylactoid skin reactions after intravenous regional anaesthesia using 0.5% prilocaine with or without preservative–a double-blind study. Acta Anaesthesiol Scand. 1995 Aug;39(6):782-4.
41. U.S. Food and Drug Administration. Parabens. Available at: http://www. fda.gov/cosmetics/productandingredientsafety/selectedcosmeticingredients/ ucm128042.htm. Updated: October 31, 2007. Accessed: October 4, 2012.
42. Boberg J, Taxvig C, Christiansen S, et al. Possible endocrine disrupting effects of parabens and their metabolites. Reprod Toxicol. 2010 Sep;30(2):301-12.
43. Health Canada. Consumer product safety: Safety of cosmetic ingredients.
44. von Woedtke T, Schluter B, Pflegel P, et al. Aspects of the antimicrobial efficacy of grapefruit seed extract and its relation to preservative substances contained. Pharmazie. 1999 Jun;54(6):452-6.
45. Brandin H, Myrberg O, Rundlof T, et al. Adverse effects by artificial grapefruit seed extract products in patients on warfarin therapy. Eur J Clin Pharmacol. 2007 Jun;63(6):565-70.
46. Schirmer BC, Langsrud S. Evaluation of natural antimicrobials on typical meat spoilage bacteria in vitro and in vacuum-packed pork meat. J Food Sci. 2010 Mar;75(2):M98-M102.
47. Kunicka-Styczynska A, Sikora M, Kalemba D. Antimicrobial activity of lavender, tea tree and lemon oils in cosmetic preservative systems. J Appl Microbiol. 2009 Dec;107(6):1903-11.
48. Fratianni F, De Martino L, Melone A, et al. Preservation of chicken breast meat treated with thyme and balm essential oils. J Food Sci. 2010 Oct;75(8):M528-35.
49. Hakkim FL, Mathiraj, Essa MM, et al. Evaluation of food protective property of five natural products using fresh-cut apple slice model. Pak J Biol Sci. 2012 Jan;15(1):10-8.
50. Erler C, Novak J. Bisphenol a exposure: human risk and health policy. J Pediatr Nurs. 2010 Oct;25(5):400-7.
51. Kamrin MA. Phthalate risks, phthalate regulation, and public health: a review. J Toxicol Environ Health B Crit Rev. 2009 Feb;12(2):157-74.

¹Department of Dermatology and Skin Science, University of British Columbia, Vancouver, BC, Canada
²Division of Dermatology, St. Paul’s Hospital, Vancouver, BC, Canada

ABSTRACT

Parabens are preservatives used in a variety of personal care, cosmetic, pharmaceutical and food products. Studies have confirmed the ubiquitous presence of parabens, with levels detected in wastewater, rivers, soil and house dust. Parabens have also been detected in human tissues and bodily fluids, but it is the discovery of these chemical compounds in the breast tissue of patients with breast cancer that has raised public concern over their use. It is hypothesized that the estrogenic properties of parabens may play a role in breast cancer development. However, studies investigating the health effects of parabens are conflicting. At this point, there is an insufficient amount of data suggesting serious consequences from paraben use and exposure to warrant drastic avoidance measures or government regulations.

Key Words:
parabens, preservatives, cosmetic products, breast cancer, spermatotoxicity, regulations, environment

Introduction

Parabens are preservatives that are used in a wide range of cosmetic, pharmaceutical and some food products. Parabens are esters of para-hydroxybenzoic acid and commonly include methylparaben, ethylparaben, propylparaben and butylparaben.¹ The recent health concerns regarding parabens stem from a study published in 2004 that detected parabens in breast tissue from patients with breast cancer.² Public pressure has persuaded several governments to introduce regulations on the use of parabens in consumer products. In this review, we examine the data regarding the health effects of parabens to provide physicians and patients with a better understanding of this issue.

Consumer Products and Parabens

Parabens have been used in food, cosmetic and pharmaceutical products since the 1930s. Their use in cosmetic consumer products is more prevalent than their utility elsewhere. Products found to contain parabens include hand soap, body lotion, shampoo, conditioner, face lotion, facial cleansers, foundation, lipstick, mascara, hair spray/mousse/gel, toothpaste and sunscreen.^1,3,4 One study identified parabens in 44% of cosmetics tested.³ In personal care products tested in the US, concentrations of methylparaben up to 1.0% were found, with lipsticks containing the highest concentration ranging from 0.15% to 1.0%.¹ The other parabens are used at concentrations lower than methylparaben in personal care products. Methylparaben and propylparaben are the most commonly used parabens in pharmaceutical products at concentrations of up to 20%;¹ both of these preservatives are also used in food products such as jams, jellies, fillings and toppings at concentrations of up to 0.1%.^1,5

Parabens in the Environment

Parabens have been found in urban streams into which treated or untreated effluent from wastewater treatment plants flows.^6,7 Consequently, these chemical compounds have been identified in rivers and drinking water sources.^6,8 Parabens have been detected in soil from agricultural fields, possibly from irrigation or fertilization practices.^9,10 The dust in houses has also been found to contain parabens.^11,12 Although commercially used parabens are of synthetic origin, some parabens are produced by living organisms, specifically by plants and microbes, e.g., a marine bacterial strain belonging to the genus Microbulbifer.¹³ Plants such as blueberries, carrots, olives, strawberries and others produce parabens (mainly methylparaben) for its presumed antimicrobial activity.^14-16 Overall, the concentrations of parabens within the environment are low with water concentrations around 7 ng/L and effluent concentrations up to 6 µg/L, soil concentrations range from 0.5 to 8 ng/g while house dust contained up to 2400 ng/g.7-11

Parabens in the Human Body

Parabens can enter the human body through the skin and parenterally. The average daily total personal paraben exposure is estimated to be 76 mg, with cosmetics and personal care products accounting for 50 mg, 25 mg from pharmaceutical products, and 1 mg from food.^17-19 Parabens applied to the skin are metabolized by keratinocyte carboxylesterases and the conjugated metabolites are excreted in urine and bile.^20,21 Oral or intravenous parabens are metabolized by esterases within the intestine and liver.¹ Parabens have been detected in urine, serum, breast milk and seminal fluid, but most worrisome has been the detection in breast tissue from patients with breast cancer.^2,22-26 Some have hypothesized that the higher concentration in the upper lateral breast near the axilla correlates with exposure from underarm deodorant and an increased incidence of breast cancer development in the area.^27,28 Still absolute concentrations indicate that levels of paraben within human fluids and tissue are low with average urine concentrations reported in the US ranging from 0.5 to 680 ng/mL and breast tissue concentrations ranging from 0 to 5100 ng/g of breast tissue (the median being 85.5 ng/g).^25,26 These low concentrations should be interpreted in the context of known estrogenic effects of parabens, which are discussed in the next section.

Toxicity and Adverse Effects of Parabens

Human and animal studies have failed to show that parabens have any acute toxicity by various routes of administration. As such, many of the studies examining paraben toxicity have focused on the long-term effects of chronic exposure.

The estrogenic activity of parabens was first identified in 1998 and has since been validated in vitro and in vivo.^1,29,30 Parabens bind human estrogen receptors, although with affinities 10,000 to 1,000,000 times less than estradiol.^29,31 Butylparaben and propylparaben have higher estrogenic activity than methylparaben or ethylparaben, but butylparaben and propylparaben are detected at concentrations 10 to 1000 times less than methylparaben in humans.³² The estrogenic effects in vivo have been demonstrated by uterotrophic (uterine growth) assays in mice and rats.^1,33 However, this effect did not prevent implantation of a fertilized egg, which is considered the most sensitive measure of estrogen toxicity.^33,34 As mentioned, it has been hypothesized that the estrogenic activity of parabens may promote breast cancer development. The concentration of estradiol in normal human breast tissue is 55.3 pg/g, suggesting there is a safety margin of 10 to 1000 times for parabens to approximate normal estradiol activity.^1,25,32 The paraben breast cancer data shows no or low parabens in a subset of patients and there are no comparisons with normal controls.^2,25 Hence, having not established a clear correlation, it is difficult to put forth a causal relationship between parabens and breast cancer development.

Another major area of study has been the effect of parabens on the male reproductive system, but findings are conflicting.³⁵ One in vitro study found that human sperm were not viable when exposed to parabens at concentrations of 1 mg/mL.³⁶ In vivo studies in mice did not replicate this result, with no spermatotoxic effects at paraben concentrations of 1%.³⁷ Conflicting results have also been reported in rats, with one study showing decreased sperm number and activity while another study found no adverse reproductive effects.^35,38 In humans, men with fertility problems including low sperm count and decreased motility were assayed for paraben exposure by measuring urine paraben levels.²³ No correlation between sperm count or motility and parabens levels was found.

Parabens, as is the case for many preservatives, can be allergenic in a small subset of the population. This sensitization commonly manifests as an eczematous rash. The rates of reported sensitization to parabens range from 0.5% to 3.5%.¹⁷ These rates of sensitization are amongst the lowest of all preservatives.^17,18 In addition, there are reports of immediate immunoglobulin Emediated allergic reactions to parabens resulting in urticaria and, in one case, bronchospasm.^39,40 However, these immediate allergic reactions are extremely rare.

Government and Regulatory Control of Parabens

Government regulatory boards have examined parabens and most have agreed that current concentrations of parabens are safe for consumer use. The European Union (EU) has set up limits on paraben use that have also been reviewed by the European Scientific Committee on Consumer Products (SCCP). In 2006, the SCCP concluded that parabens can be safely used in cosmetic products at concentrations of 0.4% for any individual paraben and 0.8% for total paraben concentrations.^1,41 These limits echo the legislative limits put in place by the EU. The Danish government went further in 2011 by banning the use of parabens in personal care products intended for children younger than 3 years of age. This decision is based on the possibility of high systemic absorption from an immature metabolism and skin barrier dysfunction.⁴² In the United States, the Cosmetic Ingredient Review (CIR) assesses ingredients for safety and is reviewed by the US Food and Drug Administration (FDA). The CIR has recommended the same maximum paraben concentrations as suggested by the SCCP and as legislated by the EU.¹ However, it should be noted that the CIR recommendations are only guidelines and manufacturers are not required to follow them. Likewise in Canada, there are no laws regulating paraben concentrations, but Health Canada agrees with the FDA and the CIR in regards to the safety of parabens and the adoption of maximum concentration guidelines.⁴³

Alternatives to Parabens

There are numerous preservatives that could be used in place of parabens. Some other commonly used preservatives include formaldehyde, quaternium-15, imidazolidinyl urea, diazolidinyl urea and dimethyloldimethyl hydantoin.¹⁸ These preservatives more commonly cause allergic reactions and some pose more serious health implications, such as formaldehyde and its causal link with cancer.¹⁸ The use of “natural” preservatives has been advocated, including grapefruit seed extract (GSE).⁴⁴ Unfortunately, GSE can interact with medications due to its ability to inhibit CYP3A4, an important enzyme involved in drug metabolism.⁴⁵ Other natural preservatives include thymol, cinnamaldehyde, allyl isothiocyanate, citric acid, ascorbic acid and rosemary extract.^46,47 These natural preservatives inhibit microbial growth in vitro, but the few studies testing antimicrobial activity in food products have provided equivocal results.^46,48,49 Therefore, further studies to determine their efficacy, safety and toxicology are warranted before widespread use.

Conclusion

The expectation of long shelf lives and microorganism-free consumer products mandates the use of preservatives. Ideally, preservatives should be active at low concentrations against a wide variety of microorganisms without interfering with other ingredients in the product, while also remaining nontoxic to humans and available at low cost to manufacturers. Parabens have been used for over 80 years and, despite reports of adverse reactions, they have proven to be amongst the safest and most well tolerated preservatives. Although the possible association of parabens with decreased sperm quality and breast cancer does warrant continued examination, the current data does not support drastic regulations or personal restrictions to exposure. Other recently regulated chemicals, such as phthalates and bisphenol A, may serve as archetypes for continued vigilance and investigation.^50,51

References

1. Cosmetic Ingredient Review Expert Panel. Final amended report on the safety assessment of Methylparaben, Ethylparaben, Propylparaben, Isopropylparaben, Butylparaben, Isobutylparaben, and Benzylparaben as used in cosmetic products. Int J Toxicol. 2008;27(Suppl 4):1-82.
2. Darbre PD, Aljarrah A, Miller WR, et al. Concentrations of parabens in human breast tumours. J Appl Toxicol. 2004 Jan;24(1):5-13.
3. Yazar K, Johnsson S, Lind ML, et al. Preservatives and fragrances in selected consumer-available cosmetics and detergents. Contact Dermatitis. 2011 May;64(5):265-72.
4. Witorsch RJ, Thomas JA. Personal care products and endocrine disruption: A critical review of the literature. Crit Rev Toxicol. 2010 Nov;40(Suppl 3):1-30.
5. Wang L, Zhang X, Wang Y, et al. Simultaneous determination of preservatives in soft drinks, yogurts and sauces by a novel solid-phase extraction element and thermal desorption-gas chromatography. Anal Chim Acta. 2006 Sep;577(1):62-7.
6. Yamamoto H, Tamura I, Hirata Y, et al. Aquatic toxicity and ecological risk assessment of seven parabens: individual and additive approach. Sci Total Environ. 2011 Dec;410-411:102-11.
7. Gonzalez-Marino I, Quintana JB, Rodriguez I, et al. Simultaneous determination of parabens, triclosan and triclocarban in water by liquid chromatography/ electrospray ionisation tandem mass spectrometry. Rapid Commun Mass Spectrom. 2009 Jun;23(12):1756-66.
8. Pedrouzo M, Borrull F, Marce RM, et al. Ultra-high-performance liquid chromatography-tandem mass spectrometry for determining the presence of eleven personal care products in surface and wastewaters. J Chromatogr A. 2009 Oct;1216(42):6994-7000.
9. Ferreira AM, Moder M, Laespada ME. Stir bar sorptive extraction of parabens, triclosan and methyl triclosan from soil, sediment and sludge with in situ derivatization and determination by gas chromatography-mass spectrometry. J Chromatogr A. 2011 Jun;1218(25):3837-44.
10. Perez RA, Albero B, Miguel E, et al. Determination of parabens and endocrinedisrupting alkylphenols in soil by gas chromatography-mass spectrometry following matrix solid-phase dispersion or in-column microwave-assisted extraction: a comparative study. Anal Bioanal Chem. 2012 Mar;402(7): 2347-57.
11. Ramirez N, Marce RM, Borrull F. Determination of parabens in house dust by pressurised hot water extraction followed by stir bar sorptive extraction and thermal desorption-gas chromatography-mass spectrometry. J Chromatogr A. 2011 Sep;1218(37):6226-31.
12. Wang L, Liao C, Liu F, et al. Occurrence and human exposure of p-hydroxybenzoic acid esters (parabens), bisphenol A diglycidyl ether (BADGE), and their hydrolysis products in indoor dust from the United States and three East Asian countries. Environ Sci Technol. 2012 Nov 6;46(21):11584-93.
13. Peng X, Adachi K, Chen C, et al. Discovery of a marine bacterium producing 4-hydroxybenzoate and its alkyl esters, parabens. Appl Environ Microbiol. 2006 Aug;72(8):5556-61.
14. Kang YH, Parker CC, Smith AC, et al. Characterization and distribution of phenolics in carrot cell walls. J Agric Food Chem. 2008 Sep;56(18):8558-64.
15. Sellappan S, Akoh CC, Krewer G. Phenolic compounds and antioxidant capacity of Georgia-grown blueberries and blackberries. J Agric Food Chem. 2002 Apr;50(8):2432-8.
16. Huang WY, Zhang HC, Liu WX, et al. Survey of antioxidant capacity and phenolic composition of blueberry, blackberry, and strawberry in Nanjing. J Zhejiang Univ Sci B. 2012 Feb;13(2):94-102.
17. Cashman AL, Warshaw EM. Parabens: a review of epidemiology, structure, allergenicity, and hormonal properties. Dermatitis. 2005 Jun;16(2):57-66.
18. Sasseville D. Hypersensitivity to preservatives. Dermatol Ther. 2004;17(3): 251-63.
19. Soni MG, Carabin IG, Burdock GA. Safety assessment of esters of p-hydroxybenzoic acid (parabens). Food Chem Toxicol. 2005 Jul;43(7): 985-1015.
20. Darbre PD, Harvey PW. Paraben esters: review of recent studies of endocrine toxicity, absorption, esterase and human exposure, and discussion of potential human health risks. J Appl Toxicol. 2008 Jul;28(5):561-78.
21. Pedersen S, Marra F, Nicoli S, et al. In vitro skin permeation and retention of parabens from cosmetic formulations. Int J Cosmet Sci. 2007 Oct;29(5):361-7.
22. Frederiksen H, Jorgensen N, Andersson AM. Parabens in urine, serum and seminal plasma from healthy Danish men determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS). J Expo Sci Environ Epidemiol. 2011 May;21(3):262-71.
23. Meeker JD, Yang T, Ye X, et al. Urinary concentrations of parabens and serum hormone levels, semen quality parameters, and sperm DNA damage. Environ Health Perspect. 2011 Feb;119(2):252-7.
24. Ye X, Bishop AM, Needham LL, et al. Automated on-line column-switching HPLC-MS/MS method with peak focusing for measuring parabens, triclosan, and other environmental phenols in human milk. Anal Chim Acta. 2008 Aug;622(1-2):150-6.
25. Barr L, Metaxas G, Harbach CA, et al. Measurement of paraben concentrations in human breast tissue at serial locations across the breast from axilla to sternum. J Appl Toxicol. 2012 Mar;32(3):219-32.
26. Calafat AM, Ye X, Wong LY, et al. Urinary concentrations of four parabens in the U.S. population: NHANES 2005-2006. Environ Health Perspect. 2010 May;118(5):679-85.
27. Darbre PD. Environmental oestrogens, cosmetics and breast cancer. Best Pract Res Clin Endocrinol Metab. 2006 Mar;20(1):121-43.
28. Harvey PW. Parabens, oestrogenicity, underarm cosmetics and breast cancer: a perspective on a hypothesis. J Appl Toxicol. 2003 Sep;23(5):285-8.
29. Routledge EJ, Parker J, Odum J, et al. Some alkyl hydroxy benzoate preservatives (parabens) are estrogenic. Toxicol Appl Pharmacol. 1998 Nov;153(1):12-9.
30. Harvey PW, Darbre P. Endocrine disrupters and human health: could oestrogenic chemicals in body care cosmetics adversely affect breast cancer incidence in women? J Appl Toxicol. 2004 May;24(3):167-76.
31. Blair RM, Fang H, Branham WS, et al. The estrogen receptor relative binding affinities of 188 natural and xenochemicals: structural diversity of ligands. Toxicol Sci. 2000 Mar;54(1):138-53.
32. Golden R, Gandy J, Vollmer G. A review of the endocrine activity of parabens and implications for potential risks to human health. Crit Rev Toxicol. 2005 Jun;35(5):435-58.
33. Shaw J, deCatanzaro D. Estrogenicity of parabens revisited: impact of parabens on early pregnancy and an uterotrophic assay in mice. Reprod Toxicol. 2009 Jul;28(1):26-31.
34. Daston GP. Developmental toxicity evaluation of butylparaben in Sprague- Dawley rats. Birth Defects Res B Dev Reprod Toxicol. 2004 Aug;71(4):296-302.
35. Kang KS, Che JH, Ryu DY, et al. Decreased sperm number and motile activity on the F1 offspring maternally exposed to butyl p-hydroxybenzoic acid (butyl paraben). J Vet Med Sci. 2002 Mar;64(3):227-35.
36. Song BL, Li HY, Peng DR. In vitro spermicidal activity of parabens against human spermatozoa. Contraception. 1989 Mar;39(3):331-5.
37. Oishi S. Effects of butyl paraben on the male reproductive system in mice. Arch Toxicol. 2002 Jul;76(7):423-9.
38. Oishi S. Lack of spermatotoxic effects of methyl and ethyl esters of p-hydroxybenzoic acid in rats. Food Chem Toxicol. 2004 Nov;42(11):1845-9.
39. Grzanka A, Misiolek H, Filipowska A, et al. Adverse effects of local anaesthetics – allergy, toxic reactions or hypersensitivity. Anestezjol Intens Ter. 2010 Oct;42(4):175-8.
40. Kajimoto Y, Rosenberg ME, Kytta J, et al. Anaphylactoid skin reactions after intravenous regional anaesthesia using 0.5% prilocaine with or without preservative–a double-blind study. Acta Anaesthesiol Scand. 1995 Aug;39(6):782-4.
41. U.S. Food and Drug Administration. Parabens. Available at: http://www. fda.gov/cosmetics/productandingredientsafety/selectedcosmeticingredients/ ucm128042.htm. Updated: October 31, 2007. Accessed: October 4, 2012.
42. Boberg J, Taxvig C, Christiansen S, et al. Possible endocrine disrupting effects of parabens and their metabolites. Reprod Toxicol. 2010 Sep;30(2):301-12.
43. Health Canada. Consumer product safety: Safety of cosmetic ingredients.
44. von Woedtke T, Schluter B, Pflegel P, et al. Aspects of the antimicrobial efficacy of grapefruit seed extract and its relation to preservative substances contained. Pharmazie. 1999 Jun;54(6):452-6.
45. Brandin H, Myrberg O, Rundlof T, et al. Adverse effects by artificial grapefruit seed extract products in patients on warfarin therapy. Eur J Clin Pharmacol. 2007 Jun;63(6):565-70.
46. Schirmer BC, Langsrud S. Evaluation of natural antimicrobials on typical meat spoilage bacteria in vitro and in vacuum-packed pork meat. J Food Sci. 2010 Mar;75(2):M98-M102.
47. Kunicka-Styczynska A, Sikora M, Kalemba D. Antimicrobial activity of lavender, tea tree and lemon oils in cosmetic preservative systems. J Appl Microbiol. 2009 Dec;107(6):1903-11.
48. Fratianni F, De Martino L, Melone A, et al. Preservation of chicken breast meat treated with thyme and balm essential oils. J Food Sci. 2010 Oct;75(8):M528-35.
49. Hakkim FL, Mathiraj, Essa MM, et al. Evaluation of food protective property of five natural products using fresh-cut apple slice model. Pak J Biol Sci. 2012 Jan;15(1):10-8.
50. Erler C, Novak J. Bisphenol a exposure: human risk and health policy. J Pediatr Nurs. 2010 Oct;25(5):400-7.
51. Kamrin MA. Phthalate risks, phthalate regulation, and public health: a review. J Toxicol Environ Health B Crit Rev. 2009 Feb;12(2):157-74.