Since the 1980s, in fact, a variety of state, national and international organizations have assessed the health effects of styrene and deemed it not harmful to humans if managed using the accepted guidelines.
However, in 2004, the U.S. National Toxicology Program (NTP), under the U.S. Department of Health and Human Services (HHS), received a recommendation from an unidentified private individual to assess the health effects of styrene. The resulting decision, in June 2011, was to list styrene in the 12th Report on Carcinogens (RoC), officially labeling it as “reasonably anticipated to be a human carcinogen.”
Chemical and composites industry trade associations responded swiftly, petitioning the Obama Administration and HHS Secretary Kathleen Sebelius to delist styrene.
Summarizing succinctly all of the reasons that the NTP chose to list styrene in the RoC is nearly impossible (but see “Learn More” for online assistance toward that end). But it can be noted here that the NTP listed the styrene-butadiene data in the Delzell study, leukemia risk in the Kolstad study, DNA damage in rat studies and lung tumors in the mouse study, among other correlations as the reasons for its listing.
The RoC also says: “Studies in the reinforced-plastics industry provided evidence that suggests a possible association between styrene exposure and cancer of the esophagus or pancreas.”
Lunn says that under current NTP policy, delisting a material from the RoC is possible, but doing so requires new scientific data that, when evaluated under the NTP’s criteria, is sufficient to remove the chemical as a carcinogenic threat. “If you want to nominate a material for delisting, which can be done at any time, there must be new data,” she says.
Since 1980, eight chemicals have been delisted from the RoC, the last one being Saccharin, in 1998. Lunn could not comment on the possibility of a delisting of styrene via political or other avenues.