October 29, 2020

California to List Molybdenum Trioxide, Indium Tin Oxide as Known Carcinogens

The California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment (OEHHA) intends to list molybdenum trioxide and indium tin oxide as known to the state to cause cancer under the Safe Drinking Water and Toxic Enforcement Act of 1986. The Act, also known as Proposition 65, requires businesses to warn California residents about significant exposures to chemicals that cause cancer or have reproductive toxicity.

OEHHA cites the International Agency for Research on Cancer’s (IARC) classification of molybdenum trioxide and indium tin oxide as chemicals that are possibly carcinogenic to humans as part of the basis for its determination. IARC’s classification is based on “sufficient evidence” of the chemicals’ carcinogenicity in experimental animals.

An article published online in The Lancet Oncology that summarizes IARC’s evaluation describes molybdenum trioxide as “a high-production-volume chemical with rare natural occurrence.” According to the Agency for Toxic Substances and Disease Registry, molybdenum is commonly found in the environment in the form of molybdenum trioxide or molybdenum salts. People are often exposed to low levels of molybdenum every day, mostly in food.

Indium tin oxide is a low-production-volume chemical primarily used to produce transparent conductive films on glass or plastic panels used in electronic devices, according to the Lancet Oncology article.

OEHHA is accepting public comments related to its notice of intent until Nov. 23, 2020. For further details, see OEHHA’s website.