On June 19, 2015, the California Office of Environmental Health Hazard Assessment added ethylene glycol as a reproductive toxicant under Proposition 65 pursuant to the authoritative bodies listing mechanism. OEHHA based its listing on a 2004 monograph authored by the National Toxicology Program Center for the Evaluation of Risks to Human Reproduction (NTP-CERHR). In that monograph, NTP-CERHR concluded that ethylene glycol causes developmental effects at high doses in rodents. Significantly, OEHHA limited the listing to the oral ingestion route of exposure. The warning requirement for this chemical will become effective June 19, 2016.
A number of groups opposed the listing, and several groups submitted post-2004 studies demonstrating that no developmental effects are seen in rabbits (as opposed to rodents) even at high doses causing maternal toxicity. Further, significant physiological similarities between rabbit and human embryology strongly suggest that ethylene glycol would not cause developmental effects in humans either. Thus, the commenters argued that developmental effects of ethylene glycol exposure in humans is not biologically plausible, thereby precluding the listing under the authoritative bodies listing regulations.
OEHHA responded to those comments. The agency acknowledged that the post-2004 studies “are well-designed and provide scientifically valid data for consideration.” After summarizing those studies, however, OEHHA concluded that “these data have not established that developmental toxicity from high oral exposures to [ethylene glycol] is NOT biologically plausible.” (Emphasis in original.)
It remains to be seen whether this listing will trigger a legal challenge. Ethylene glycol is used in many consumer products, including automotive antifreeze, hydraulic brake fluids, plastics and films. Thus, this listing may result in a significant wave of enforcement actions across diverse industries. Absent a legal challenge reversing it, what may save the regulated community from frivolous enforcement may be the ingestion limitation on route of exposure and the high dose, acknowledged even by OEHHA, necessary to see effects even in the more sensitive rodent species.