Stories about the development of tumors in mice caused by styrene exposure concerned many in the composites industry when they first appeared. Since humans, like mice, are mammals, people started to worry that styrene might have a similar affect on industry employees and community members. At the March 2011 annual meeting of the Society of Toxicology in Washington, D.C., toxicologists presented new styrene study results based on the latest research, which uses genetically modified mice to test styrene’s potential carcinogenicity. This work—relying on techniques that won the Nobel Prize in physiology and medicine in 2007—belays fears that there is a link between styrene and tumors in humans.

Styrene, a component used to produce polyester resins for composites, polystyrene and many other common materials, has been the subject of scientific examination to determine human health affects, including cancer risk, from exposure to the chemical for over 20 years. Researchers have concluded from extensive data that a link to cancer in humans is not scientifically supportable, according to the Styrene Information and Research Center (SIRC), an industry group of styrene manufacturers and users, which has a long-standing commitment to health-effects research.

SIRC has commissioned more than $20 million in scientific research since its founding in 1987 to understand styrene’s potential health effects. Two recent expert weight-of-the-evidence reviews of the extensive styrene health effects database have shown that styrene is not likely to cause cancer in humans. Yet government regulators in the U.S. National Toxicology Program (NTP) have expressed concern that styrene exposure might be a cancer risk and have proposed to officially list it as “reasonably anticipated” to be a human carcinogen.

Styrene pathology slides

These four pathology slides show the differences in mouse lung sections both with and without styrene exposure for a normal mouse and a mouse that had been genetically modified by making the CYP2F2 gene inactive. The slide at top left (A) shows the terminal bronchioles in a normal mouse with zero exposure to styrene. Top right (B) is from a normal mouse exposed to 400 mg/kg of styrene for five days. Notice the widespread evidence of toxicity. In contrast, the slide at bottom left (C), from a modified mouse with no styrene exposure is essentially unchanged at bottom right (D) after 400 mg/kg of styrene exposure for 5 days.

The American Composites Manufacturers Association (ACMA) has been working closely with SIRC, receiving the latest research findings and scientific information from the organization and putting it before government policy makers to ensure that it gets heard, according to John Schweitzer, ACMA senior director of government affairs. A key mission of the ACMA is public sector advocacy, representing the composites industry before government regulators and legislators and before non-government organizations that promulgate codes and standards.