Some ingredients used in nail products have been tied to cancer, miscarriages, lung diseases and other ailments. The industry has long fought regulations.

Each time a customer pulled open the glass door at the nail shop in Ridgewood, Queens, where Nancy Otavalo worked, a cheerful chorus would ring out from where she sat with her fellow manicurists against the wall: “Pick a color!”

Ms. Otavalo, a 39-year-old Ecuadorean immigrant, was usually stationed at the first table. She trimmed and buffed and chatted about her quick-witted toddler, or her strapping 9-year-old boy. But she never spoke of another dreamed-for child, the one lost last year in a miscarriage that began while she was giving a customer a shoulder massage.

At the second table was Monica A. Rocano, 30, who sometimes brought a daughter to visit. But clients had never met her 3-year-old son, Matthew Ramon. People thought Matthew was shy, but in fact he has barely learned how to speak and can walk only with great difficulty.

A chair down from Ms. Rocano was another, quieter manicurist. In her idle moments, she surfed the Internet on her phone, seeking something that might explain the miscarriage she had last year. Or the four others that came before.

Similar stories of illness and tragedy abound at nail salons across the country, of children born slow or “special,” of miscarriages and cancers, of coughs that will not go away and painful skin afflictions. The stories have become so common that older manicurists warn women of child-bearing age away from the business, with its potent brew of polishes, solvents, hardeners and glues that nail workers handle daily.

A growing body of medical research shows a link between the chemicals that make nail and beauty products useful — the ingredients that make them chip-resistant and pliable, quick to dry and brightly colored, for example — and serious health problems.

Whatever the threat the typical customer enjoying her weekly French tips might face, it is a different order of magnitude, advocates say, for manicurists who handle the chemicals and breathe their fumes for hours on end, day after day.

The prevalence of respiratory and skin ailments among nail salon workers is widely acknowledged. More uncertain, however, is their risk for direr medical issues. Some of the chemicals in nail products are known to cause cancer; others have been linked to abnormal fetal development, miscarriages and other harm to reproductive health.

A number of studies have also found that cosmetologists — a group that includes manicurists, as well as hairdressers and makeup artists — have elevated rates of death from Hodgkin’s disease, of low birth-weight babies and of multiple myeloma, a form of cancer.

But firm conclusions are elusive, partly because the research is so limited. Very few studies have focused on nail salon workers specifically. Little is known about the true extent to which they are exposed to hazardous chemicals, what the accumulated effect is over time and whether a connection can actually be drawn to their health.

The federal law that regulates cosmetics safety, which is more than 75 years old, does not require companies to share safety information with the Food and Drug Administration. The law bans ingredients harmful to users, but it contains no provisions for the agency to evaluate the effects of the chemicals before they are put on shelves. Industry lobbyists have fought tougher monitoring requirements.

Industry officials say their products contain minuscule amounts of the chemicals identified as potentially hazardous and pose no threat.

“What I hear are insinuations based on ‘linked to,’” said Doug Schoon, co-chairman of the Professional Beauty Association’s Nail Manufacturers Council on Safety. “When we talk about nail polish, there’s no evidence of harm.”

Health advocates and officials disagree, pointing to the accumulated evidence.

“We know that a lot of the chemicals are very dangerous,” said David Michaels, the assistant labor secretary who heads the federal Occupational Safety and Health Administration, which oversees workplace safety. “We don’t need to see the effect in nail salon workers to know that they are dangerous to the workers.”

So many health complaints were cropping up among the mostly Vietnamese manicurists in Oakland, Calif., that workers at Asian Health Services, a community organization there, decided on their own to investigate about a decade ago.

“It was like, ‘Oh wow, what’s happening in this community?’” said Julia Liou, who is now the health center’s director of program planning and development and a co-founder of the California Healthy Nail Salon Collaborative. “We are seeing this epidemic of people who are sick.”

The organization helped form a coalition in California that pushed for restrictions on chemicals used in nail salons, but the cosmetics industry succeeded in blocking a ban.

In recent years, in the face of growing health concerns, some polish companies have said that they have removed certain controversial chemicals from their products. But random testing of some of these products by government agencies showed the chemicals were still present.

Some states and municipalities recommend workers wear gloves and other protection, but salon owners usually discourage them from donning such unsightly gear. And even though officials overseeing workplace safety concede that federal standards on levels of chemicals that these workers can be exposed to need revision, nothing has been done.

So manicurists continue to paint fingertips, swipe off polish and file down false nails, while absorbing chemicals that are potentially hazardous to their health.

“There are so many stories but no one that dares to tell them; no one dares to tell them because they have no one to tell,” Ms. Otavalo said in an interview on a day off from the Ridgewood salon, babysitting for her colleague’s developmentally disabled son, Matthew. (Ms. Otavalo left her job at the salon a few months ago.) “There are thousands of women who are working in this, but no one asking: ‘What’s happening to you? How do you feel?’ We just work and work.”