On October 17, 2022, an epidemiological study published in the Journal of the National Cancer Institute reported an increased risk of uterine cancer among women who used chemical hair straighteners and related products (e.g., dyes, bleach), relative to those who did not use such products. Specifically, Chang et al. (2022) reported a uterine cancer hazard ratio, or HR, of 1.80 (95% CI = 1.12-2.88) among women who had a history of hair straightener use in a cohort of 50,884 women followed from 2003 to 2009 (the “Sister Study”). Put simply, this means that, according to the study’s authors, women who had used hair straighteners had an 80% higher risk of developing uterine cancer than those who had not. Moreover, Chang et al. (2022) reported that one additional case of uterine cancer was expected for every 85 ever hair straightener users (women who used a product at least once) and one additional uterine cancer for every 42 frequent hair straightener users (women who used a product >4 times per year).

Numerous popular press outlets, as well as the NIH’s own website, reported on the findings from Chang et al (2022). Subsequently, an October 21, 2022, court filing alleged that a 32-year-old woman’s uterine cancer was caused by use of hair straightening products, including those produced under brand names L’Oreal, Strength of Nature, Soft Sheen, Dabur, and Namaste. Specific to the first court case, the plaintiff alleged that her uterine cancer was associated with exposure to unspecified endocrine disrupting chemicals (EDCs) and phthalates, including di-2-ethylhexyl phthalate (DEHP), present in hair straightening products. Scientifically, the claim lacks merit in that the latency period is far too short for the hair dye to be causal even if one believed that the dye posed a cancer risk.

The International Agency for Research on Cancer (IARC) classifies DEHP as “possibly carcinogenic to humans” based on limited evidence that exposure of adequate frequency, intensity, and duration may be attributed to liver cancers in test animals (IARC, 2018). The magnitude of risk to hair straightener end consumers is based on user absorbed dose, duration of exposure, and frequency of exposure. The likelihood that a specific compound can cause uterine cancer is also a function of latency between compound exposure and date of disease onset. It is important to note that the general population is exposed to various phthalates and other EDCs through many activities of daily life, such as contact with upholstery and clothing, lubrication oil and paint use, and leaching from food packaging (ATSDR, 2022; NIEHS, 2022).

It is noteworthy that Chang et al. (2022), as an epidemiological study, could not characterize the delivered dose among the women who alleged exposure. Instead, the authors simply categorized exposure based on frequency of product use (e.g., “1-2 times per year,” “every 3-4 months,” “every 5-8 weeks”). This, along with other study limitations such as small sample size for certain product subtypes and use of self-reported diagnostic data, limit the extent to which the results of Chang et al. (2022) can be generalized to hair products users nationwide.

How Paustenbach & Associates Can Help

Personal injury litigation associated with personal care products such as shampoos and hair straightening products has increased in recent years. Scientists at Paustenbach & Associates have over 40 years of experience in conducting risk assessments of trace contaminants, including phthalates, in the workplace, ambient environment, point source emissions, and consumer products, as well as foods. In the cases for which we were retained, we applied exposure science and the health risk assessment methodology embraced by the National Academy of Science to characterize the possible risks. We have published an analysis of the human health risks of hair straightener use (Pierce et al., 2011). We have also published numerous risk assessments of personal care products in scientific journals (Monnot et al., 2018; Fung et al., 2018; Drechsel et al., 2018a,b; Towle et al., 2018; Novick et al., 2013). Please contact Jonathan Heywood for more information regarding our capabilities at jheywood@paustenbachandassociates.com.

References

Agency for Toxic Substances Disease Registry (ATSDR). 2022. Toxicological Profile for Di(2-Ethylhexyl)Phthalate (DEHP).

Chang, C.J., K.M. O’Brien, A.P. Keil, S.A. Gaston, C.L. Jackson, D.P. Sandler, and A.J. White. 2022. Use of Straighteners and Hair Products and Incident Uterine Cancer. Journal of the National Cancer Institute, djac165.

Drechsel, D.A., K.M. Towle, E.S. Fung, R.M. Novick, D.J. Paustenbach, and A.D. Monnot. 2018. Chemical stability analysis of hair cleansing conditioners under high-heat-conditions experienced during hair styling processes. Cosmetics. 5(1):23. doi: 10.3390/cosmetics5010023.

Drechsel, D.A., K.M. Towle, E.S. Fung, R.M. Novick, D.J. Paustenbach, and A.D. Monnot. 2018. Skin sensitization induction potential from daily exposure to fragrances in personal care products. Dermatitis. 29(6)324-331.

Fung, E.S., R.M. Novick, D.A. Drechsel, K.M. Towle, D.J. Paustenbach, and A.D. Monnot. 2018. Tier-based skin irritation testing of hair cleansing conditioners and their constituents. Cutaneous Ocular Tox:1-4.

IARC Working Group on the Evaluation of Carcinogenic Risks to Humans. 2018. Benzene. International Agency for Research on Cancer. 

Monnot, A.D., K.M. Towle, E.M. Warshaw, E.S. Fung, R.M. Novick, D.J. Paustenbach, and D.A. Drechsel. 2018. Skin sensitization induction risk assessment of common ingredients in commercially available cleansing conditioners. Dermatitis. 30(2):116-128.

Novick, R.M., M.L. Nelson, K.M Unice, J.J. Keenan, and D.J. Paustenbach. 2013. Estimation of the safe use concentrations of the preservative 1,2-benzisothiazolin-3- one (BIT) in consumer cleaning products and sunscreens. Food Chem Tox. 56:60-66.

Towle, K.M., D.A. Drechsel, E.M. Warshaw, E.S. Fung, R.M. Novick, D.J. Paustenbach, and A.D. Monnot. 2018. A quantitative risk assessment of the skin sensitization induction potential of the Kathon CG preservative in rinse-off and leave-on personal care and cosmetic products. Dermatitis 29(3):132-138. doi: 10.1097/DER.0000000000000359.