The phone rang incessantly in Dr. Tamarra James-Todd’s office at Harvard’s T.H. Chan School of Public Health. “I’m sorry,” she said, excusing herself for the third time. “It’s happening a lot,” she explained after pausing to take another call, “with the F.D.A. thing.”

The research has finally begun to bear fruit: A robust body of scientific evidence has now shown that straighteners and other hair products marketed to Black girls and women have been linked to endocrine-disrupting substances associated with the early onset of menstruation and many of the reproductive-health issues that follow, from uterine fibroids, preterm birth and infertility to breast, ovarian and uterine cancer. Many of these hormone-health-related problems are more common in Black women than in other women, including an aggressive form of breast cancer that contributes to a death rate from the disease that is 28 percent higher than the rate for white women.

The evidence took a drastic turn in October 2022 when the Sister Study, which was led by the National Institute of Environmental Health Sciences and followed a cohort of nearly 34,000 women, found that those who frequently used chemical hair-straightening products, a majority of whom were Black women, were two and a half times as likely to develop uterine cancer as those who did not use the products. Uterine cancer is the most common cancer of the female reproductive system, and the most aggressive subtypes have been on the rise since 2000 — especially among Black women.

The Sister Study, and several studies that followed, including work from James-Todd’s lab, represents a significant step forward, offering compelling scientific evidence of what has been long suspected. Over the past year and a half, this research has prompted lawsuits involving nearly 9,000 plaintiffs across the country and at least the promise of new action from the federal government.

“I think we’re sitting in a moment in time,” James-Todd told me in her office as her phone continued to ring in the days after the news of the F.D.A. proposal, “where — even if it’s just for a second, because I’m not sure how long it’s going to last — we know that there’s value in doing health-disparities research. We know that there is value in focusing in on the health of women of color.” Until recently, she said, “it was always the sidelined topic.” But now the momentum was palpable: “There’s a real passion to do this work. And I do think it’s brought on by the coming together of policies, holding companies accountable through legal actions, holding the government accountable.”

Under the lax oversight by the American government, even the package labeling can’t be trusted. A 2018 scientific report conducted by Silent Spring Institute, an environmental-health research organization, was built on a list supplied by James-Todd of 18 different hair products marketed to and used by Black women; Silent Spring found dozens of chemicals that can disrupt hormones — but 84 percent of the toxic ingredients weren’t listed on the packaging. Several studies have found higher levels of endocrine-disrupting chemicals in the urine of Black women compared with that of white women.

This means that even as the evidence is increasingly harder to ignore or deny, consumers remain shockingly unprotected, leading to an entirely preventable continuing public-health crisis. Most of the studies have been published in science journals that never reach the general public. Many Black people have quietly wondered for years whether hair relaxers were safe, but burning scalps and even hair loss have been normalized as the price of desirably straight hair.

In his 2009 documentary “Good Hair,” Chris Rock memorably showed an aluminum soda can submerged in a beaker of sodium hydroxide, or lye, which was until fairly recently a main ingredient in relaxers: After four hours, it had disintegrated. In the 2022 Hulu series “The Hair Tales,” Oprah Winfrey recalled leaving a salon with a severely burned scalp after a relaxer treatment in 1977. Every time she combed or washed her hair, clumps of it fell out.

For this article, reported over more than a year, I interviewed dozens of people: scientists at universities, government agencies and nonprofit health organizations; subjects taking part in medical studies; plaintiffs in lawsuits; politicians; historians; activists; and lawyers. I created an extensive database of studies, articles and reports, dating to the 1990s, about Black hair products, hormonally related health issues and their intersection, ranging from a tiny observational study with only four subjects to longitudinal studies with tens of thousands of participants that compare risk factors and health outcomes over decades.

The question remains: Why are hair products marketed aggressively to Black women still on the market with so little oversight, even amid growing documentation of the extent of the harm? When I asked an F.D.A. spokeswoman why the endocrine-disrupting chemicals called phthalates are not banned for use in cosmetics, including hair relaxers, in the United States as they are in Europe, she replied in an email that “at the present time, the F.D.A. does not have evidence that phthalates as used in cosmetics pose a safety risk.”

“I’m not saying that more research isn’t needed, but there’s study after study,” James-Todd said. “At some point you have evidence enough to start making recommendations that people reduce their use of these products or don’t use them at all.”

“I hate to say it,” she added, “but in the U.S., we don’t care. It’s about the money.”

Black people, and particularly Black women, have had a centuries-old, complicated relationship to our hair. It has been a source of style, creativity and pride, as well as pain, insult and discrimination. In the early 1900s, as hundreds of thousands of Black people migrated from the South to cities in the North to find employment in factories or as washerwomen and maids working in white homes, Black women made damaging efforts to straighten their hair in order to be perceived as presentable and professional rather than unsophisticated and “country.”

My grandmother migrated from Mississippi to Chicago in the late 1920s and refused to work as a domestic like her sisters. She couldn’t afford Walker’s school and instead went to Miss Lydia’s Beauty College, a less expensive knockoff. (I still remember the neighborhood women, decades later, sitting in our kitchen to get their hair shampooed, pressed and curled; the sight of the stovetop flames licking the hot comb as it went from black to red-hot; the acrid smell of burning hair.)

The African American inventor Garrett A. Morgan has been credited with developing the first chemical relaxer, but the products would not explode into wide use until the 1950s, when George E. Johnson, a Chicago chemist, invented a more effective formula using sodium hydroxide as the active ingredient. It worked by breaking down the protein structure of the hair in order to loosen the natural curls. Johnson and his wife, Joan, brought Ultra Sheen, a relaxer targeted to Black women, to the market in 1957, and it became a sensation.

Johnson Products became the first Black-owned company to be listed on the American Stock Exchange, controlling 60 percent of the Black hair-care market by 1975. Its success attracted a flood of competitors, most of them other Black-owned companies headquartered in Chicago. Johnson’s biggest rivals were Carson Products, the maker of the enormously popular Dark & Lovely, and SoftSheen, the manufacturer of Care Free Curl. But even as these Black companies were capitalizing on a societal standard, a counterculture was emerging.

The Black Power Movement of the 1960s and ’70s fostered a Black Is Beautiful ethos and a new silhouette and symbol: the Afro. Even so, the mainstream pressure to wear straight hair remained pervasive, and my grandmother stopped speaking to my mother, my sister and me for several weeks in the mid-’70s when we went natural with Angela Davis-style Afros.

In 1998, Carson Products bought Johnson Products for $70 million; in 2000, the French cosmetic company L’Oréal acquired Carson. L’Oréal also snapped up SoftSheen, paying a combined price estimated at $370 million for the two companies and absorbing 20 percent of the Black hair-care market. The industry was booming — and selling chemically relaxed hair to a new generation with kits that were themselves objects of desire, decorated in pastels, flowers, butterflies and photos of smiling little-girl models with their hair hanging in glossy dark sheets.

James-Todd grew up during this boom, and she remembers her Black-girl rite of passage at 8 years old: getting her hair relaxed for the first time. As she sat in the chair at a salon in Kansas City, Mo., in 1987, with thick white goo covering her head, she imagined herself with the long, straight hair she’d seen on family members. Then her scalp began to burn. As she squirmed, she recalls, her mother told her: “Hold still. This is how it’s supposed to feel.” That evening, as she brushed her hair, it fell out in handfuls.

As it turned out, several of the young models who became mini-celebrities as the faces of Pretty-n-Silky, Beautiful Beginnings, Just for Me and other relaxers targeted to children would reveal decades later that they never used the products themselves — or had long ago stopped chemically relaxing their hair — and instead straightened their hair with heat.Many Black women do use heat to straighten their hair, by blow drying, flat ironing or pressing the hair in salons or at home with instruments more advanced than the hot comb my grandmother used. But when the hair gets wet — when it is washed or during a rainstorm, in a swimming pool or after a vigorous workout — it reverts to its natural state. My mother didn’t learn to swim until her 70s, because as a child she wasn’t allowed to get her hair wet; it would “go back,” and my grandmother would have to start the time-consuming straightening process all over again.

Working women and busy mothers often feel that they don’t have the time or the money to spend on that laborious routine, making chemical relaxers an easier and much more affordable option. That helps explain why a vast majority of Black women have used relaxers at some point in their lives.

D. Wendy Greene, a professor and the director of the Center for Law, Policy and Social Action at the Drexel Kline School of Law in Philadelphia, points to social and financial penalties for Black hair that doesn’t conform to this standard. “Generally speaking, I have not seen any policy,” she notes, “that says you have to wear straight hair.” However, “you have policies that prohibit ‘extreme’ hairstyles or ‘unnatural’ or ‘unprofessional’ hairstyles. That creates a straight-hair expectation or mandate that affects gaining entry into the workplace or maintaining your employment.”

Five years ago, California became the first state to pass the CROWN Act (for Creating a Respectful and Open World for Natural Hair), legislation that makes this kind of hair discrimination illegal. Twenty-three other states and 50 cities have passed similar legislation, along with the House of Representatives, though that bill stalled in the Senate. Representative Ayanna Pressley, a Massachusetts Democrat and a sponsor of the federal CROWN Act, recalls the pressure she felt to straighten her hair as a young congressional aide in the mid-1990s. “I remember one time sitting in the chair, and I was being burned very aggressively,” Pressley recalls. (Pressley is now bald not because of relaxers but because of the autoimmune disease alopecia.) “But I said, ‘I’m going to grit my teeth and bear it,’ because I had bought fully into the idea that in order for me to appear professional, I needed my hair to be as straight as possible.”

Greene, who had her first relaxer applied when she was a young girl and her last 18 years ago at age 29, says: “Many people think hair is not that big of a deal — it’s harmless, it’s a choice. But it’s actually more complicated than that. If you do care about Black women’s and girls’ health, you have to care about our hair.”

Women have long been overlooked in scientific research, and Black women have been nearly invisible. The scientists who began to push against those barriers found that they were often met with skepticism and even outright resistance. It wasn’t until 1995 that a team at Howard and Boston Universities, frustrated by the lack of research that could explain the longstanding disproportionately poor health outcomes of Black American women, recruited 59,000 participants to participate in the newly created Black Women’s Health Study. (I joined in the first wave of volunteers.) Two years later, the investigators asked their first questions about chemical hair straighteners.

Dr. Yvette Cozier is now a principal investigator for the study and was at the time a doctoral student at Boston University who served as research coordinator in the early days of the project. She remembers the conversations as the group designed questionnaires that might illuminate why Black women were more likely to be diagnosed with an aggressive late-stage form of breast cancer at earlier ages.

Back then, it was assumed that Black women lacked education, information and access to health care, which led to a delay in diagnosis. But the scientists decided to also consider what kinds of substances their cohort of Black women might have been exposed to. “The external pressure to have straight hair came up,” Cozier recalls, “and the use of hair relaxers as something that was started so early in life, used over and over again. And there were some people who said, ‘Well, white women get perms.’ I said: ‘No, no, no. We’re not talking about the same thing, though. And if they want to keep their hair curly and decide they don’t want to keep their hair bone-straight,’” she explained to her colleagues, “ ‘society’s not going to yell at them.’”

Cozier told them that she was speaking from experience: “I said I got my first perm when I was 12.” Though she now shaves her head by choice, she continued relaxing her hair, she recalls, for years after recognizing the importance of the issue. “For a Black woman, we did not have as many acceptable options.”

The team added several questions about relaxers: age at first use, frequency of use, total number of years used, type of formulation and number of scalp burns during application. Burns and abrasions, caused when the product is applied to the scalp, give the chemicals an efficient entryway into the body. The researchers would follow 48,167 women for the next six years.

James-Todd was at Boston University herself around this same time, as a student in the master’s program in public health. In 2000, she took an introductory environmental-health class taught by an associate professor named Nancy Irwin Maxwell. For research that would be published later that fall, Maxwell had combed through nearly 500 issues of women’s magazines dating from 1950 to 1994 and found that ads for hair-care products containing synthetic and natural hormones that can alter the body’s endocrine system appeared only twice in the sampled issues of Mademoiselle and never in Ladies’ Home Journal, mainly read by white women. In Essence and Ebony, well-known publications aimed at Black women, more than 70 such hair or scalp products were advertised.

Studies conducted over the previous decade suggested that the synthetic hormones or endocrine disrupters, a class of chemicals that can mimic hormones or block the action of natural hormones, were associated with premature puberty in children. A related study was published in 1998 by Dr. Chandra M. Tiwary, then the chief of pediatric endocrinology at Brooke Army Medical Center in San Antonio. He noticed breast development and pubic hair in four of his Black patients who were under 8 years old and could find no medical explanation until he asked their parents to bring in any cosmetics used on the children. He was alarmed to find high levels of female hormones in the hair products, which were explicitly marketed to Black children. Tiwary says he wrote to the F.D.A. sharing his concerns but never received a reply. “I was surprised,” he recalls, “that parents were using these products without knowledge that they contain very powerful hormones.”

Maxwell’s research — which cited Tiwary’s study in the footnotes — and a Time magazine cover story that October titled “Early Puberty: Why Girls Are Growing Up Faster” sparked what James-Todd calls “an ‘aha!’ moment” that would shift the course of her scientific career. The article mentioned a landmark study of 17,000 American subjects, which found that girls in the mid-1990s started to develop breasts, usually the first sign of puberty, around age 10, more than a year earlier than previously recorded. Even more striking: Black girls began developing breasts around age 9. A more recent study found that Black girls exhibit signs of early puberty more than twice as frequently as white girls and also earlier than girls of other ethnicities.

James-Todd began to wonder what might be missing from the research. “I thought back to that shop full of people getting relaxers every few months, using chemicals powerful enough to make my scalp burn like crazy and take my hair out,” she recalls. “Could these products be exposing people to hormonally active ingredients that could increase their risk of early onset of puberty?”

Over the next few years, as a Columbia University doctoral candidate in epidemiology, James-Todd conducted her own study of several hundred subjects in New York City that established that those who used relaxers and other hair products marketed to Black women were more likely to experience early puberty, which can trigger a cascade of reproductive-health problems that plague Black women more often than others.

For the project that would become her dissertation, James-Todd spent two years interviewing 300 women she recruited from nail and hair salons, churches, workplaces, restaurants and laundromats. She asked them which hair oils and hair relaxers they had used, the age at which they began to use the products and how long and how frequently they used them. James-Todd also asked each subject how old she was when she started menstruating. She found that hair products containing endocrine-disrupting chemicals, more likely to be used by Black women in childhood, were associated with early puberty.

It would take several years for James-Todd’s dissertation, which she finished in 2008, to be published in the journal Annals of Epidemiology. “I had a baby,” she says. “I got married. I moved.” But that wasn’t all. “There was a lot of pushback on: ‘This doesn’t make sense, to look at personal-care products. It’s only care products; you’re talking about things that are readily rinsed out.’” The message received from some advisers and editors, she says, was clear: “People not feeling like this was valuable science.” It would have been easy to be discouraged. But she wasn’t.

“I don’t think we know all the answers,” James-Todd says, “but I am going to spend my career finding out.”

Laced through many of the accounts of this network of Black female scientists is a sense of frustration at having to fight, over and over, for recognition, publication and funding for their work, even as their insights and insistence on the right research have led to increasing breakthroughs.

Cozier and her colleagues at the Black Women’s Health Study were disappointed by the initial inconclusive results of their investigation into a connection between relaxers and breast cancer. They decided to create a new study with the relaxer data, focused on a condition that was more common: uterine fibroids, which affect more than 80 percent of Black American women by age 50. Though rarely cancerous, these growths can cause painful periods, heavy bleeding and infertility — and are the leading reason for hysterectomies, which are more common in Black women than in others.

This time the researchers struck scientific gold. In their study, published in The American Journal of Epidemiology in 2012, they pinpointed an association between hair-relaxer use and the 7,146 subjects who developed fibroids — with a higher risk for women who had used the products for at least 10 years compared with those who used them rarely or not at all.

The Women’s Circle of Health Study was the next large, long-term project to examine hair-relaxer use and disease. It was established in 2003 to track breast cancer, and the earliest study questionnaire asked participants, half of whom had been diagnosed with breast cancer, about relaxer use. But the answers were not analyzed for more than a decade, after Dr. Adana Llanos, a cancer and molecular epidemiologist, became an investigator on the project. “My hypothesis was that Black women that use chemical relaxers and hair dyes would have increased risk of breast cancer and also more aggressive tumor features,” says Llanos, now on the faculty of Columbia’s Mailman School of Public Health.

Llanos was surprised when her study, published in 2017 in the journal Carcinogenesis, didn’t find an association between relaxer products and breast cancer in Black women. But she decided to take a closer look at the data with her own experience in mind. When she was growing up in West Orange, N.J., her mother used chemical relaxers on her hair and her sister’s to make it more manageable. Llanos continued using relaxers until, as a trained scientist in 2010, she grew concerned about the environmental agents and cosmetic chemicals that Black women were exposed to.

For her next study of nearly 3,000 subjects, most of them Black, rather than comparing women who had used relaxers and hair dyes with those who had never used them, she and her colleagues went deeper, adding questions about the age at which subjects began relaxing and dyeing their hair and how long they had done so. That investigation, published in the journal Environmental Research in 2022, found that women who used relaxers before age 12 and those who used the products for longer than 10 years — whether at home or in salons — were more prone to larger and more aggressive breast tumors.

“Black women are the largest consumers of hair products, but there has never been a major focus on their safety,” Llanos says. “What’s most scary to me is using these strong chemicals on children. No one wants to harm their child, but we didn’t know. I’m sure if my mom knew what we know now, we would never have had our hair relaxed.”

“I think sometimes it requires a certain accumulation of data to occur,” James-Todd says. “I don’t know if I can say that it wasn’t believed before, but sometimes it feels that way a bit.” But more scientists were now arriving in the field who brought with them the lived experience that convinced them that there were investigative clues to follow. “Thank goodness,” she says, “for Chandra Jackson and Symielle Gaston.”

The National Institute of Environmental Health Sciences, part of the National Institutes of Health, has run the federal Sister Study since 2003, recruiting more than 50,000 women ages 35 to 74 whose sisters had breast cancer. The initial study questionnaire asked about chemical-relaxer use but didn’t run the data for a connection to breast cancer until 2017.

That was the year Dr. Chandra L. Jackson joined the study as an investigator and hired Dr. Symielle Gaston as her postdoc fellow. Jackson, who is 43, says she doesn’t remember life before relaxers; she stopped using chemical straighteners 20 years ago. Gaston, who is now an N.I.E.H.S. staff scientist, says she got her first relaxer in early elementary school and used chemical straighteners into her mid-20s. “My scalp felt like it was on fire,” she recalls. “The end result made me feel like the painful experience, and the future experiences about every six weeks, were worth it. But deep inside, I knew something wasn’t right.”

As part of the interview process for fellowships, applicants are required to propose research they would work on if given the opportunity and funding. Gaston said she wanted to include hair-product-related questions in studies about racial health disparities. “It was because of our lived experience that we wanted to start pursuing that line of research that wasn’t being pursued before,” Jackson says.

In 2020, with questions about relaxer products analyzed, an association between relaxers and breast cancer emerged in the Sister Study. The research, published in The International Journal of Cancer, found a higher breast-cancer risk associated with any straightener use — and the more frequent the use, the higher the risk. Those who used straighteners at least every five to eight weeks had a 31 percent higher breast-cancer risk, compared with 18 percent for less frequent use. Hair dye also proved more dangerous for Black women: Those who used permanent hair dye within the past year had a 45 percent higher breast-cancer risk, compared with 9 percent for all women in the study. The following year, the Sister Study researchers expanded the map, co-authoring a new study in Carcinogenesis finding that frequent use of hair relaxers — more than four times a year — was also associated with ovarian cancer.

Now it was as if a dam was breaking. The landmark 2022 Sister Study investigation linking relaxer use and uterine cancer, published in The Journal of the National Cancer Institute, has since been cited by more than 570 media outlets. This time the evidence — building on decades of work that began in earnest with James-Todd’s dissertation — was much stronger: The investigators observed an 80 percent higher risk of uterine cancer among users of hair-straightening products, with the risk two and a half times as high among frequent users. An editorial by Llanos and three other Black female scientists praised the study but criticized the small sample of Black participants, who made up less than 8 percent of the cohort.

Last year, the Black Women’s Health Study built on those findings in a much larger group of Black subjects: nearly 45,000 women with no history of cancer and an intact uterus. Compared with women who never or rarely used hair relaxers, postmenopausal women who reported using hair relaxers more than twice a year or for more than five years had a greater than 50 percent increased risk of uterine cancer.

In interviews, the scientists took pains to emphasize that just because an individual woman has relaxed her hair at some point in her life, that doesn’t mean she will end up with cancer. “But what we know,” Llanos says, “is that endocrine-disrupting chemicals are in these products that are marketed to Black communities and that we use more of. And Black women are disproportionately experiencing poor outcomes from reproductive-hormone-related conditions.” She continues, “This is the red flag, the flashing light.”

The first lawsuit was filed in October 2022, just after the Sister Study research was published. Since then, advertisements on billboards, on the internet and on television blaring “Hair Straightener Uterine Cancer Lawsuit” and “Call Right Now” have recruited thousands of Black women across the country.

In February 2023, as the cases multiplied, the lawsuits were brought together into a class-action multidistrict litigation, or MDL, a federal legal procedure designed to speed the processing of complex cases, like air-disaster litigation or product-liability suits. The suit, registered as Hair Relaxer Marketing, Sales Practices and Products Liability Litigation, claims that L’Oréal USA, Revlon and other companies that make chemical straighteners knew, or should have known, that their products increased the risk of ovarian, uterine and endometrial cancer — the diseases for which the scientific evidence of a link is strongest — but manufactured and distributed them anyway, while giving no warning to consumers that they carried such risks.

This spring, eight other companies were added to the suit, which now includes more than 8,900 plaintiffs and is in the discovery phase. The litigation is being led by the ubiquitous civil rights and personal-injury lawyer Ben Crump, who has represented the families of Trayvon Martin, Breonna Taylor, Ahmaud Arbery, George Floyd and other Black people killed in high-profile violent encounters. Crump’s firm also represented plaintiffs in the Johnson & Johnson baby-powder lawsuit, which has resulted in a $6.475 billion proposed settlement following 15 years of litigation alleging that the company failed to warn customers about talcum powder’s connection to ovarian cancer.

Diandra Debrosse, a managing partner of the DiCello Levitt office in Birmingham, Ala., is leading the new case alongside Crump. “When you think about some of those chemicals in the products, there’s no question about the health issues,” Debrosse says. “But if you look at the packaging, they say ‘organic’ and ‘natural.’ We think with the hair-relaxer case will come one of the biggest reckoning moments that the cosmetics industry has had about the dangerous nature of what they’re selling to people and not disclosing.”

The companies argued last year in a motion to dismiss the litigation that the suit is “devoid of any facts” showing that they “knew or should have known that some ingredient” in the products “could cause injury.” L’Oreal, the biggest player, said in a statement that “we are confident in the safety of SoftSheen-Carson’s products and believe the allegations made in these lawsuits have neither legal nor scientific merit.” In a separate statement, Revlon said, “We do not believe the science supports a link between chemical hair straighteners or relaxers and cancer.” The judge overseeing the litigation dismissed some charges and defendants but allowed the suit to proceed.

Jenny Mitchell, a 34-year-old Black woman, is Crump and Debrosse’s lead plaintiff. She was diagnosed with uterine cancer at age 28, after using relaxer products nearly all her life. In August 2018, Mitchell, who had always wanted to have children, went to a fertility specialist. But what she thought would be a new beginning led to heart-stopping news. “During the ultrasound, the physician said, ‘I see something; I think we need to do a biopsy right now,’” she recalls. “He did a biopsy that day, and then three days later, I got a call saying that I had uterine cancer.”

A month later, to preserve her life, she had a full hysterectomy, followed by chemotherapy and radiation treatments. “When you’re diagnosed with cancer,” she says, “it’s like your world just flashes before you, and I said, ‘Dang, I’m never going to have kids.’”

Four years later, while watching the news, Mitchell heard about the study linking relaxer use to uterine cancer. She thought back to her childhood in rural Georgia, where she didn’t know any girl or woman — at school, in her family, at church — whose hair wasn’t straightened. “It was the societal norm,” she says. “Make sure your hair is neat, pressed, laid and all that stuff.”

Mitchell’s mother relaxed her hair at home. “Everybody started off with Just For Me,” Mitchell says. Aggressively marketed to children and their parents, the kit came with a cassette tape that played a bouncy theme song and claimed to be created by mothers for their daughters. “The tape was white with pink lettering on it,” Mitchell says. “I remember that vividly.”

After high school, Mitchell joined the Army. Though not explicitly required, straight hair was expected for Black women. “In the military, your hair has to lay a certain way — a bun, neat and slicked back,” Mitchell says. “When you have a certain texture of hair like mine, it’s hard to meet that standard without relaxing. To maintain that image, I had to relax my hair. A lot of people did that.”

Even after she left the military, she continued using hair relaxers. After her hysterectomy, as she continued to grieve the loss of her uterus and ability to bear children, she was watching the “Today” show and learned about the lawsuit. “Grief comes in stages, right? And so does anger,” Mitchell says. “These products never said, ‘Hey, may cause cancer.’ Millions of African American women have used this product. We have to shine the light and hold these people accountable.”

Crump says he was drawn to this case because of the women in his own family who used straightening products. “It is a tragedy,” he says, “that unbeknownst to us, this poison we put on our scalps we now know was causing cancer.”

For James-Todd, this is a moment of validation but also one of possibility. “I think two things are happening at the same time,” she says. “One is this litigation.” The other, she says, is a rising interest in what she and her network of fellow scientists have highlighted: “that the federal regulation is very poor.” “It’s not just that there’s harm done,” she says, “but the process in the system that we use is problematic, because it doesn’t protect consumers in the way that consumers think it does. And why is the U.S. so different than other countries?”

In April, the F.D.A. missed its own deadline to advance its proposed ban of formaldehyde in hair relaxers; an agency spokeswoman said in an email in May that “the proposed rule continues to be a high priority and is still in the rule-making process.” Even if the ban is approved, it could take months to go into effect. In the meantime, the products still fill shelves and salons and in recent months have even enjoyed something of a revival on social media, where TikTok videos hashtagged #relaxerisback have received more than 24 million views. A top video with more than 71,000 likes shows a young Black woman with bone-straight hair, captioned “creamy crack, I’m back — I don’t regret going back to relaxer one bit.” In another video, a woman offers a before-and-after relaxer tutorial, showing the goop being slathered onto her natural hair and ending with swingy, straight hair and a smile.