The research in Windsor buttresses other recent work on breast cancer and chemicals. A French study in 2011, for example, found elevated risks among women who worked in plastics, rubber and textile manufacturing. A study from Mexico in 2010 found that the presence of metabolites of phthalates—softening agents for plastics that have endocrine-disrupting properties—in urine was "positively associated" with the disease. A 2007 paper from US researchers identified 216 chemicals that had been associated with mammary gland tumors in animals.
The lone American coauthor of the Windsor study, Robert Park of the National Institute for Occupational Safety and Health, said he was "surprised by how strong the findings were. There was a lot of confirmation of prior concerns, which is always the goal but not always achieved by these kinds of studies."
"Race to the Bottom"
The Canadian plastics workers say they have little faith in their country's system of workplace regulation. Factory inspections are haphazard, they say, and chemical standards in many cases are weak, meaning few overexposures—by the legal definition, anyway—are cited. Conditions improve incrementally, if at all.
"We're sitting here after three decades, and you see the weight of the evidence that these substances pose serious health problems, yet there's nary a mention of the risk that blue-collar workers bear, particularly women. They're just not on the radar."
"It's a race to the bottom," said Sari Sairanen, national health and safety director for the Canadian Auto Workers union, which represents about 4,000 workers in parts plants, some of which make plastics. "For the worker, there's the fear of losing your job or the fear of retribution from your employer if issues are raised."
Bristow, a union member, said that many workers seem unwilling to confront their bosses with health questions. Too often, she said, a woman disappears from the factory floor and her coworkers don't learn until much later that another case of breast cancer has been diagnosed.
The Ontario Ministry of Labor is committed to the prevention of work-related diseases, a spokesman said in a statement. The ministry uses a multifaceted approach that includes health and safety inspection "blitzes" and the updating of exposure limits, the spokesman wrote. "We make decisions on the latest science and we welcome any report that will bring a better understanding of occupational exposures to ensure that workers are protected from unsafe exposure levels."
There is also deep dissatisfaction with workplace regulation in the United States. Adam Finkel, former director of health standards programs for OSHA, said the vast majority of exposure limits enforced by the agency in American workplaces are based on scientific data from the 1960s or earlier, even though an estimated 150 workers die each day of work-related diseases.
Limits for only 16 substances have been updated, a consequence of industry challenges and hesitancy on OSHA's part. There are no limits for BPA. The limits that do exist for chemicals used in plastics—say, vinyl chloride, an ingredient in PVC—were designed to address cancer and acute symptoms, not the sort of hormonal damage that can occur when women of childbearing age receive low-level exposures. Only 18 percent of OSHA inspections last year focused on potential health, as opposed to safety, hazards.
"It's a terrible record, and I'm getting more pessimistic as the years go by," said Finkel, who runs the Penn Program on Regulation, a research center at the University of Pennsylvania Law School.
In its statement, OSHA acknowledged, "Many of our current Permissible Exposure Limits are out of date and inadequately protective, and we do not have limits for many other chemicals. OSHA is currently examining ways to strengthen our efforts related to workplace chemical exposures, as well as ways to respond to the identification of new, emerging hazards."
The US Environmental Protection Agency's record on chemicals—like OSHA's—is thin.
Chemicals found in the workplace—among them BPA and phthalates—also may pose health risks to the general public. Of the more than 80,000 chemicals registered for use today, however, the EPA has required only about 2 percent to undergo even basic testing. At the root of the problem is the Toxic Substances Control Act of 1976, which puts the onus on the EPA to prove that a chemical is harmful before it can be banned or its use restricted. This burden is almost insurmountably high; the EPA has banned narrow uses of only five chemicals since the law was passed.
The Obama EPA has begun to disallow claims of "confidential business information" that for decades enabled companies to conceal the identities of chemicals when they submitted health and safety data, even if significant risks had been flagged.
Industry, however, is fighting an attempt by the EPA to extend its anti-secrecy policy to new chemicals; a proposed rule has been under review by the White House Office of Management and Budget for nearly a year.
A proposal to add BPA, phthalates and a certain class of flame retardants to an EPA "chemicals of concern" list has been at the OMB for more than 900 days. The EPA says that these chemicals "may present an unreasonable risk to human health and/or the environment" and wants to use its authority under the law to list them, a step that would, among other things, require producers to notify the EPA when they exported the chemicals, and the EPA to notify the recipient governments.
Industry groups such as the US Chamber of Commerce oppose the action, saying it amounts to an unwarranted blacklisting.
An EPA spokesman did not respond to requests for comment. An OMB spokesman declined to comment.
The US Food and Drug Administration no longer allows the use of BPA in baby bottles or infant-training cups. The FDA acted, however, only after receiving a petition from the American Chemistry Council, which said that manufacturers of these products had already abandoned the chemical to meet consumer preference. "The agency continues to support the safety of BPA for use in products that hold food," an FDA spokeswoman said in a written statement.
The Canadian government didn't wait for an industry petition. It banned BPA in baby bottles two years ago, based on concerns about the chemical's toxicity.
Brophy, one of the researchers in Windsor, approves of the ban. But he worries about the women in the plastics plants, who soak up BPA and other chemicals on the job.
"There seems to be widespread concern about consumer exposures but almost no concern for the most highly exposed population—the blue-collar workers," he said. "These women remain invisible and their cancer risk largely ignored."
The Center for Public Integrity is a nonprofit, independent investigative news outlet in Washington, DC. For more of its stories go to publicintegrity.org.