Excess breast cancer risk among women employed in automobile plastics facilities

A recently published case-control study involving more than 2,100 women in southern Ontario, Canada reported a strong association between being employed in the automotive plastics industry and breast cancer. The researchers recruited the 'case' subjects between 2002-2008 among newly diagnosed breast cancer patients and the randomly-selected controls from the same geographic area.  The researchers examined a variety of risk factors for breast cancer (e.g., reproductive history, age) and collected data on the women's employment history.  Elevated odds of breast cancer were found among women employed in several occupations (e.g., canned food manufacturing, laundry/dry cleaning and bars/gambling establishments) but the highest and most robust finding was among women who worked in automotive plastics manufacturing.  Depending on the statistical model used, these women had between two and five times the risk of breast cancer compared to the reference groups.

The authors, including James T Brophy, PhD and Margaret Keith, PhD, of the University of Stirling’s Occupational and Environmental Health Research Group, hypothesized that chemicals used in plastics and their downstream production may be a critical link to breast cancer risk.  Many plastics contain and release compounds that mimic estrogens and/or are endocrine disrupting compounds (EDCs).  Plastics also contain known human carcinogens including vinyl chloride, styrene, formaldehyde and butadiene.   The authors report that the women who participated in the study were involved primarily in plastics injection molding, in which:

"molten mixtures of resins, monomers, multiple additives and sometimes lamination films are formed into plastic pieces of defined dimensions and configuration.  Emissions of vapors or mists from these hot processes can include plasticizers, ultraviolet-protectors, pigments, dyes, flame-retardants, un-reacted components and decomposition products.  Further exposure comes from skin contact in handling and performing finishing tasks."

The Toronto Sun and the Center for Public Integrity (CPI) reported first on these study results (here, here) in mid-November.  CPI's Jim Morris spoke to the affected workers who describe conditions in the plants, especially in the past:

"Hot plastic would be removed from the molding machines and dumped on the floor, where it might lie for up to an hour.  ...the lack of local ventilation...is still the norm at many facilities."

The experiences of these workers and other insights from the study authors are presented in a companion paper, "Chemical exposures of women workers in the plastics industry with particular references to breast cancer and reproductive hazards," published in New Solutions.  The lead author, Robert DeMatteo and his colleagues, note that in southern Ontario, Canada---across the river from the Detroit, Michigan-based auto industry----the small auto plastics manufacturing plants are dominated by women workers.

"75 percent of the small manufacturing plants have fewer than 20 employees, are not unionized, are economically marginal with low technological development, and have precarious employment as a result of the restructuring of manufacturing in the global economy."

The workers paint of picture of the ubiquitous sources of exposure in their workplaces to the plastic compounds and other toxic substances:

"I looked behind the mold and I could see a big cloud of smoke and then there was a fire and...the smoke is clearing and here is one of our workers in the middle of it.  You couldn't even see here and it was just plastic burning."

"...the parts were frequently spray-painted with gray paint.  Since we were close-by, we could also get a dose of spray paint all over us.  It was everywhere.  We would look like the 'Tin Man' in the Wizard of Oz."

DeMatteo and his colleagues describe the ineffective regulatory system that is charged with protecting workers' health and safety.

  "Although inspection reports and workers' observations indicate that dust and fumes were constant problems and ventilation was inadequate, hygiene sampling did not find levels above the occupational exposure limits."

Moreover, neither the Canadian nor U.S. worker safety systems are equipped to address the complex mixtures of chemical in this type of manufacturing.  As one woman workers said to the authors:

"We are pretty much being exposed to different materials every day... like one machine was ABS, another machine was nylon and they were ten feet away from each other."

Another woman added:

"What's the synergistic effect of everything being mixed together?"

The authors conclude their New Solutions paper with these observations:

• The working conditions for plastics workers is "very poor" and enforcement is "an unmitigated failure."
• Plastics workers are chronically exposed to compounds and mixtures of chemicals that are potential carcinogens and endocrine disruptors.
• Workers carry a body burden of plastics-related contaminants that far exceed those found in the general public.
• Women in the plastics industry are developing breast cancer and experiencing adverse reproductive effects as a result of exposures in their workplaces.
•  Many plastics-related compounds are endocrine disruptors with adverse effects at very low levels.  The ability of these materials to  "disrupt the endocrine system at low levels lends biological plausibility to the link between workplace exposures and increased risk of breast cancer and reproductive problems for women working in the plastics industry."

Both the case-control study published in Environmental Health and the review appearing in New Solutions were supported by the Canadian National Network on Environments and Women's Health, with funding from the federal agency Health Canada.