How Large is the Hair Relaxer Potential Claimant Pool?

In this study, we will present an analysis to estimate the size of the potential pool of African-American claimants for the hair relaxer multi-district litigation. We did not use other ethnicities such as Hispanics, Hispanic-Black or Jewish as we did not have data to estimate usage of chemical hair straighteners among these populations.

Census Data

We start with decennial US Census data from 2000¹, 2010 and 2020² in addition to the 1-Year American Community Survey data for 2011-2019, 2021-2022³ to estimate the size of the non-Hispanic Black (as defined by US Census) female population for the past 5, 10, and 20 years. Since 2020 the number of Americans identifying solely as Black alone has decreased, while the number of Americans identifying as Black-Hispanic or multiracial has increased⁴.

National Cancer Institute’s SEER Data

Next, we use the National Cancer Institute’s Surveillance Epidemiology and End Results (SEER) to determine uterine & ovarian cancer rates for non-Hispanic Blacks^{5 6}.

How Many Non-Hispanic Black Women Were Diagnosed with Uterine or Ovarian Cancer?

We apply the National Cancer Institute’s SEER incidence data for non-Hispanic Blacks to the population estimates derived from US Census data.

Time Frame	# of Years	Uterine Cancer Cases	Ovarian Cancer Cases
2008-2022	5	31,858	2,359
2013-2022	10	62,126	13,840
2003-2022	20	108,792	39,931

How Many Cases Qualify Based on Medical Criteria?

Our next step is to reduce the potential claimant pool by using the medical criteria provided by MDL leadership. We estimate that 90% of uterine cancers are type I endometrial, and 25% of ovarian cancers are non-serous.

Up to 10% of uterine body cancers are sarcomas, so the actual numbers for endometrial cancer cases and deaths are slightly lower than these estimates.

https://www.cancer.org/cancer/types/endometrial-cancer/about/key-statistics.html

. . around a quarter of cases consist of non-serous epithelial ovarian cancer (EOC), which is a heterogeneous group of malignancies that includes endometroid, mucinous, clear cell carcinoma (CCC), and carcinosarcoma.

https://pubmed.ncbi.nlm.nih.gov/32787339/

This reduces the number of potential claimants based on injuries to the following number.

Time Frame	# of Years	Uterine Cancer Cases	Ovarian Cancer Cases
2018-2022	5	28,672	2,359
2008-2022	10	55,914	3,460
2003-2022	20	97,913	9,983

How Many Injuries Qualify Based on Usage Criteria?

The most recent criteria provided by MDL leadership appears to be based on the Use of Straighteners and Other Hair Products and Incident Uterine Cancer research paper authored by K. The study defines “frequent use” (>4 times per year), compares it to the “no use” population and finds an association with increased incidence of uterine cancer.

The recently released Hair relaxer use and risk of uterine cancer in the Black Women’s Health Study in the Environmental Journal concludes that long-term use of chemical hair relaxers was associated with increased risk of uterine cancer among postmenopausal women. I believe this study provides a stronger statistical basis for the association of chemical hair straighteners and uterine cancer than the paper based on the NIEHS Sister Study.

The BWHS uterine cancer paper also gives more insight into chemical hair straightener usage in the non-Hispanic Black community and defines:

• • 10%: “never/light” reported using them for <4 years and <= 2 times per year.

• • 37%: “heavy” reported >= 15 years of use and >= 5 times/year.

• • 53%: “moderate” was reported for all other users.

Focusing only on heavy users of chemical hair straighteners, we estimate the lower boundary of the potential claimant pool as follows:

Time Frame	# of Years	Uterine Cancer Cancers	Ovarian Cancer Cancers
2018-2022	5	10,609	873
2013-2022	10	20,688	1,280
2003-2022	20	36,228	3,694

This analysis focuses solely on the non-Hispanic Black population and serves as a lower bound for estimating the size of the potential claimant pool.

“Moderate” use in the report was defined as any participant that did not fit into “never/light” or “heavy” use categories. The report further breaks usage by Duration of Use and Frequency of Use as measured by Person Years. For copyright reasons, I am not providing data tables, but will summarize the information:

• • 57% of non-Hispanic Black women in the study used hair relaxer more than 5 times a year.

• • 86% of non-Hispanic Black women in the study used hair relaxer for a duration more than 5 years.

It seems plausible that individuals using hair relaxers more than five times a year would correlate to a longer overall duration of usage over time. Let’s assume that frequency and duration of use are are positively correlated. Using this assumption, we come up with our final estimates. We use 37% for our low estimate, the definition of “heavy” usage in the study, 57% for our medium estimate, usage of hair relaxer more than five times a year, and 86% our high estimate for usage longer than five years for low, medium, and high estimates.

Time Frame	# of Years	Low Estimate	Medium Estimate	High Estimate
2018-2022	5	10,609	16,343	24,658
2013-2022	10	20,688	31,871	48,086
2003-2022	20	36,228	55,810	84,205

1. 2000 The Black Population ↩︎
2. Population by Race 2010 & 2020
   ↩︎
3. 1-Year American Community Survey: ↩︎
4. The Growing Diversity of Black America ↩︎
5. SEER Explorer Uterine Cancer Incidence Rates for Non-Hispanic Black Females ↩︎
6. SEER Explorer Ovarian Cancer Incidence Rates for Non-Hispanic Black Female ↩︎
7. Use of Straighteners and Other Hair Care Products and Incident Uterine Cancer, Bertrand, et al. ↩︎