Issues around listing chemicals under Prop 65

In 1986, California voters passed the Safe Drinking Water and Toxic Enforcement Act, most commonly referred to by its ballot title, “Prop 65.” Prop 65 is a statewide “right-to-know” act that prohibits businesses from exposing California citizens to carcinogens and reproductive toxicants without clear and reasonable warning, except when there is no significant risk of exposure to such chemicals. California’s Office of Environmental Health Hazard Assessment (OEHHA) has since been charged with the responsibility of implementing Prop 65.

One contentious issue presented by Prop 65 is the “authoritative body mechanism” by which chemicals may be listed as carcinogens and reproductive toxicants. This mechanism is one of four that OEHHA may employ when listing a chemical, and it is used often. Through the “authoritative body mechanism,” a chemical may be listed as a carcinogen or reproductive toxicant if it is deemed so by a designated agency, outside of California State government.

OEHHA has identified several agencies as authoritative bodies, including the International Agency for Research on Cancer (IARC), and the National Toxicology Program’s Center for the Evaluation of Risks to Human Reproduction (NTP-CERHR). If one of these agencies makes a determination that a chemical is a carcinogen or a reproductive toxicant, OEHHA will then conduct a limited evaluation to determine whether that chemical should be listed under Proposition 65. A second mechanism that is employed by Prop 65 is the “labor code mechanism,” which relies solely on IARC assessments when making a determination on a chemical.

Once a chemical is listed, businesses may be subject to the warning requirement if their product will expose a consumer to the chemical. To assist businesses in determining whether they are subject to the warning requirement, OEHHA may issue regulatory safe harbor levels for each chemical. For products containing chemicals known to cause cancer, this means that a business must give clear and reasonable warning (generally on the product’s label) to that effect unless the exposure level is below the “no significant risk level” (NSRL). For products containing chemicals listed as reproductive toxicants, a business must give clear and reasonable warning unless the exposure level is below the “maximum allowable dose level” (MADL).

While Prop 65 does not require OEHHA to issue safe harbor levels (i.e., NSRLs, MADLs), OEHHA may, and they are often helpful. Without regulatory safe harbor levels on which to rely, businesses often choose to include a Prop 65 warning on their products even if there is little or no exposure to the Prop 65 listed chemical so that they can be certain to avoid any risk of litigation.

OEHHA ironically discourages businesses from expounding on the content of product labeling, and so Prop 65 warnings often lack the specificity necessary to ensure the public receives useful information about potential risk from exposures. As a result, these warnings steer the consumer to focus more on identifying potential hazards without the necessary information to understand the actual risk of harm from exposure so that they make informed purchasing decisions. Hazard based warnings thus leave consumers confused. However, with proper safe harbor levels to guide businesses, some of this confusion can be eliminated.

As helpful as issuing safe harbor levels can be, OEHHA often issues them inconsistently, and rarely at the same pace as it lists chemicals. As of January 27, 2017, 970 chemicals have been listed under Proposition 65 since its enactment in 1986, and most of these chemicals were listed before 1991. Yet, only about 32% of these chemicals have regulatory safe harbor levels.

In the last 10 years, 134 chemicals were listed, but less than 10% have corresponding regulatory safe harbor levels. During this time period, it took on average approximately 16 months to issue a regulatory safe harbor level from the time the chemical was listed, but in some instances, it took 3 years to issue a regulatory safe harbor level.

Seemingly, in an effort to pick up the proverbial slack in assigning safe harbor levels to chemicals listed under Prop 65, OEHHA has issued safe harbor levels for at least six chemicals in the past two months. However, at least two of these chemicals, glyphosate and ethylene glycol, should not have been listed in the first place because their determinations under the authoritative body mechanism were flawed, thus raising the question:

Is OEHHA wasting valuable time and state resources by listing chemicals that are overwhelmingly recognized as safe? The answer is a resounding YES.                                                                          


OEHHA recently added glyphosate, the single most used chemical in agriculture and the main ingredient in the herbicide Roundup, to its list of chemicals “Known to the State to Cause Cancer.” Using the labor code mechanism, OEHHA based this decision on a monograph published by IARC. And because a decision based a labor code mechanism only uses data from IARC, no other outside agency’s finding were reviewed. On the same day as its listing, OEHHA also proposed to adopt a safe harbor level for the chemical.

IARC is the only known scientific organization to conclude that glyphosate is “probably carcinogenic” to humans. Organizations such as the United States EPA, New Zealand EPA, German Federal Institute for Occupational Safety and Health to the European Chemicals Agency, United Nations Food and Agriculture Organization, the European Food Safety Authority, the Canadian Pest Management Regulatory Agency, and the Australian Pesticides and Veterinary Medicines Authority have concluded that glyphosate is not a carcinogen.

In listing glyphosate, OEHHA ceded virtually all authority to IARC. The monographs that OEHHA may ultimately rely on for a listing under Proposition 65 are developed by an IARC Monographs Programme “Working Group” — a small group of scientists, hand selected by IARC itself through a “call for experts” — that summarize existing scientific studies and mechanistic data to determine whether an agent (including chemicals) is carcinogenic to humans. Based on this determination, the agent is assigned one of five categories. This approach lacks transparency, and provides limited opportunity for stakeholder engagement.

Furthermore, when relying on IARC Monograph program designations, OEHHA only invites comments that address “whether IARC has identified the specific chemical or substance as a known or potential human or animal carcinogen.” This means that it offers no administrative recourse to challenge the scientific basis of IARC’s conclusions on glyphosate, effectively allowing a completely foreign body to determine California state law.

Because of this, a business could be subject to labeling in California for a Proposition 65 cancer listing despite never having an opportunity to submit scientific data or comments to OEHHA refuting IARC’s cancer classification decision. This procedural deficiency is particularly striking in the case of glyphosate because the overwhelming scientific evidence supports the safety of glyphosate. If the public cannot offer evidence to dispute the studies considered by IARC, then why have a process for notice and comment at all?

Ethylene glycol

Ethylene glycol (EG) was also listed under the authoritative body mechanism, though as a reproductive toxicant (by ingestion). OEHHA announced its intent to list ethylene glycol in 2014 based on the conclusions of a 2004 NTP-CERHR report that evaluated EG. It was officially listed in 2015, and two years later, was assigned a regulatory safe harbor level.

NTP-CERHR initially evaluated EG because: (1) “it is  high production volume chemical,” (2) “there is widespread human exposure,” and (3) “the toxicology database on ethylene glycol includes recent data on its mechanism of action and occupational exposure information.” Ultimately, NTP-CERHR concluded that there is “negligible concern” of adverse reproductive toxicity in humans exposed to EG. However, because NTP-CERHR also concluded that “oral exposure to high doses of EG can adversely affect development in mice and rats,” OEHHA listed EG as a human reproductive toxicant.

Since the 2004 NTP-CERHR report, there have been at least 11 studies that demonstrate the flaws in relying solely on the mice studies reviewed in 2004. In sum, the studies show that there are not enough toxicokinetic similarities between mice embryos and humans to conclude that ingestion of ethylene glycol can cause reproductive toxicity in humans. The 11 more recent studies instead use other animals (namely rabbits and rats), and in vitro testing. These studies show that, rabbits, rats, and likely humans, are “less sensitive to adverse developmental outcomes.”

OEHHA was made aware of these studies, as well as determinations from Environment Canada that developmental toxicity has never been reported in human exposure. However, OEHHA dismissed evidence that suggested humans are less sensitive than rodents to the developmental toxicity of ethylene glycol. Moreover, most products with the potential to contain ethylene glycol have only trace amounts of EG that do not pose a risk to humans. These products therefore would likely never need to have an EG Prop 65 warning. Even for EG-based antifreeze and other coolants that contain relatively high levels of ethylene glycol, any adverse developmental effects in humans would only occur after ingestion of a lethal dose.

Data from the American Association of Poison Control Centers National Poison Data System show that nearly every instance of oral exposure to ethylene glycol is intentional, i.e., the result of suicide or attempted suicide. It follows that such exposure will likely not be abated by warning that ingestion of the substance may result in reproductive effects (which is all that Proposition 65 requires), since a lethal dose would have to be ingested for any reproductive effects to present themselves. Requiring a warning that ingesting antifreeze could cause reproductive harm therefore provides no public health benefit.

Finally, federal law already requires labeling of products containing significant amounts of ethylene glycol; any product containing 10% or more by weight of ethylene glycol (antifreeze typically has 50% ethylene glycol by weight) must be labeled with the signal “warning” and the statement “harmful or fatal if swallowed.” This requirement should be sufficient because, as stated above, reproductive effects would only occur if a lethal dose was ingested.

In adding glyphosate and EG to the Prop 65 list, OEHHA expended valuable resources on pointlessly listing two chemicals that do not pose any real threat to public health. Instead, OEHHA should develop regulatory safe harbor levels for the many Prop 65 chemicals already listed.

, , , , , , ,

Pin It on Pinterest