On November 19, 2014, California’s OEHHA will conduct a meeting to determine whether a group of chemicals known as Dibenzanthracenes (DBAs) should be listed as known  to cause cancer. For those of you not familiar with the OEHHA, it describes its authority and function thusly:

The California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment (OEHHA) is the lead agency for the implementation of the Safe Drinking Water and Toxic Enforcement Act of 1986 (Proposition 65). The Carcinogen Identification Committee (CIC) advises and assists OEHHA in compiling the list of chemicals known to the State to cause cancer as required by Health and Safety Code section 25249.8. The Committee serves as the State’s qualified experts for determining whether a chemical has been clearly shown through scientifically valid testing according to generally accepted principles to cause cancer.

OEHHA’s treatment of DBAs lends some insight into the workings of this agency with far-reaching authority.  It is OEHHA that mandates the use of the ubiquitous “Prop. 65 Warnings” that adorn products and buildings throughout the Golden State.

First, DBAs are five-ring polycyclic aromatic hydrocarbons (PAHs) that contain an anthracene core (three linear benzene rings). DB[a,h]A has been listed by Prop. 65 since 1988.  The same chemical was listed as “probably carcinogenic to humans” by the International Agency for Research on Cancer in 1987.  The National Toxicology Program classified DB[a,h]A as “reasonably anticipated to be a human carcinogen” in its Second Report on Carcinogens in 1981, and the U.S. Environmental Protection Agency listed it as a “probable human carcinogen” based on experimental animal evidence.   But none of these authorities have so listed DB[a,c]A or DB[a,j]A, which OEHHA now proposes to add to its list of carcinogens.

Like many other PAHs, DBAs are produced as products of incomplete combustion or pyrolysis of organic matter (e.g., cigarette and marijuana smoke, gasoline engine exhaust, and industrial emissions such as fuel combustion, coke oven operations, and coal-tar distillation) and during high temperature cooking (e.g., grilling, broiling, roasting, baking, frying).  DBAs are known to be included in the smoke of forest fires and even the campground fires one might use to toast marshmallows.

With the exception of smokers and occupationally exposed workers, most individuals are exposed to PAHs predominately from dietary sources.  DBAs are present in the air (ambient and indoor, in occupational settings and cooking fumes); in water (drinking and fresh); in dried sediments; and in food (fresh and cooked).  OEHHA reports that DBAs are present in cigarette smoke and marijuana smoke, slightly more so in marijuana smoke (0.00115 µg/ tobacco  cigarette; 0.00141 µg/ marijuana cigarette ).

DBAs have been aggressively studied for decades.  OEHHA has a page on its website titled “Evidence on the Carcinogenicity of Dibenzanthracenes,”  which has a section of references covering 10 pages.  Despite that, OEHHA notes that “[n]o data on the long-term effects of human exposure to pure DBAs were identified in the literature search conducted by OEHHA” and that “[n]o epidemiology studies were identified that investigated the risk of cancer associated with exposure specifically to DBAs.”  Nevertheless, relying on animal studies, in vivo studies and mechanistic analyses, OEHHA proposes to list the chemicals found in marijuana smoke, fresh vegetables and forest fire smoke as having been “clearly shown through scientifically valid testing according to generally accepted principles to cause cancer.”

Perhaps such a determination can be justified, but where will they put the warning labels?

PS – At the same November meeting, OEHHA will consider expanding its listing of N- nitrosomethyl-n-alkylamines (NMAs).  According to OEHHA, NMAs have been detected in personal care products, such as shampoos and conditioners, and household cleaning products, such as dishwashing liquids and surface cleaners. NMAs are not intentionally added to these products, but may form as a result of the reaction of nitrite with amine compounds.  However, the challenge as to locating warning labels on these products is perhaps somewhat lesser than that relating to DBAs.

The public has until October 13 to comment on two hazard identification documents: “Evidence on the Carcinogenicity of Dibenzanthracenes” and “Evidence on the Carcinogenicity of N-Nitrosomethyl-n-alkylamines.”