Prop 65 update

New chemicals added to the list

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Proposition 65 contains approximately 900 chemicals that are known to cause cancer or reproductive toxicity. The list grows every year and, as in the past, new chemicals have been added since January of 2023. In addition to identifying the newly-added chemicals, this article describes the process by which chemicals are considered for and thereafter added to the list.

Process of listing chemicals

The Safe Drinking Water and Toxic Enforcement Act of 1986 (Proposition 65) requires the State of California to publish a list of chemicals known to cause cancer or reproductive toxicity, and to update the list at least annually. (Health and Safety Code section 25249.8).

The statute defines four ways for a chemical to be added to the Proposition 65 list.

  1. Labor Code: The list must contain chemicals identified by reference in Labor Code section 6382(b)(1) or (d). Labor Code section 6382(b)(1) incorporates chemicals identified by the World Health Organization’s International Agency for Research on Cancer (“IARC”) as causing cancer in humans or laboratory animals.
  2. State’s Qualified Experts: Either of two independent committees of scientific and health experts can find that a chemical has been clearly shown to cause cancer or birth defects or other reproductive harm. These two committees—the Carcinogen Identification Committee (“CIC”) and the Developmental and Reproductive Toxicant Identification Committee (“DARTIC”) — meet at least once each year and are designated as the “State’s Qualified Experts” (“SQE”) for evaluation of chemicals under Proposition 65.
  3. Authoritative Bodies: The CIC and DARTIC have designated certain organizations as “authoritative bodies.” A chemical will be added to the Proposition 65 list if one of these authoritative bodies formally identifies it as causing cancer or birth defects or other reproductive harm. The following organizations have been designated as authoritative bodies: the US Environmental Protection Agency (“EPA”), US Food and Drug Administration (“FDA”), National Institute for Occupational Safety and Health (“NIOSH”), the National Toxicology Program of the US Department of Health and Human Services (“NTP”), and IARC.
  4. Formally Required to be Labeled: If an agency of the state or federal government requires that a chemical be labeled or identified as causing cancer or birth defects or other reproductive harm, it will be added to the list. Most chemicals listed in this manner are prescription drugs that are required by the FDA to contain warnings relating to cancer or birth defects or other reproductive harm.

The procedure for listing a chemical involves, at a minimum:

  • Public notice that a chemical is under consideration for listing;
  • A public comment period;
  • Review of comments received; and
  • Notice of the final decision.

With the above in mind, we now turn to the newly listed chemicals.

Chemicals added to the list since January 1, 2023

Anthracene:

A component of coal tar, Anthracene is used in the production of the red dye alizarin and other dyes. It is also used in wood preservatives, insecticides and coating materials. Exposure to humans occurs mainly through tobacco smoke and ingestion of food contaminated with combustion products.

Anthracene was added to the list (effective August 11, 2023) based on the IARC’s conclusion that the chemical is classified in Group 2A as “probably carcinogenic to humans.”

2-Bromopropane:

This chemical is a colorless liquid that is used to manufacture other chemicals, drugs, and dyes. It is also known as Isopropyl Bromide and 2-Propyl Bromide.

2-Bromopropane was added to the list (effective August 11, 2023) based on the IARC’s conclusion that the chemical is classified in Group 2B as “possibly carcinogenic to humans.”

Dimethyl hydrogen phosphite:

This chemical is used in a variety of ways: to make insecticides and herbicides; as a lubricant additive; an adhesive; a flame retardant for fabrics; a stabilizer in oil and plaster; and as a steel corrosion inhibitor in combination with pyrocatechol.

Dimethyl hydrogen phosphite was added to the list (effective August 11, 2023) based on the IARC’s conclusion that the chemical is classified in Group 2B as “possibly carcinogenic to humans.”

1,1,1-Trichloroethane:

This chemical, also known as methyl chloroform and chloroethene, was once produced industrially in large quantities for use as a solvent. It is regulated by the Montreal Protocol as an ozone-depleting substance and its use is being rapidly phased out. Prior thereto, it was widely used for cleaning metal parts and circuit boards, as a photoresist solvent in the electronics industry, as an aerosol propellant, as a cutting fluid additive, and as a solvent for inks, paints, adhesives, and other coatings. 1,1,1-Trichloroethane is also used as an insecticidal fumigant.

It was also the standard cleaner for photographic film (movie/slide/negatives, etc.). Other commonly available solvents damage emulsion and base (acetone will severely damage triacetate base on most films), and thus are not suitable for this application. The standard replacement, Forane 141 is much less effective, and tends to leave a residue. 1,1,1-Trichloroethane was used as a thinner in correction fluid products such as liquid paper. Many of its applications previously used carbon tetrachloride (which was banned in US consumer products in 1970). In turn, 1,1,1-trichloroethane itself is now being replaced by other solvents in the laboratory.

1,1,1-Trichloroethane was added to the list (effective April 21, 2023) based on the IARC’s conclusion that the chemical is classified in Group 2A as “probably carcinogenic to humans.”

Leucomalachite Green:

This chemical is a triphenylmethane dye used as a detection method for latent blood in forensic science.

Leucomalachite Green was added to the list (effective April 21, 2023) based on the IARC’s conclusion that the chemical is classified in Group 2B as “possibly carcinogenic to humans.”

1-Bromo-3-Chloropropane:

This chemical is primarily, if not solely, used as an intermediate for organic synthesis (i.e. pharmaceuticals)

1-Bromo-3-Chloropropane was added to the list (effective January 27, 2023) based on the IARC’s conclusion that the chemical is classified in Group 2B as “possibly carcinogenic to humans” based on sufficient evidence of carcinogenicity in animals and strong evidence in experimental systems that it exhibits key characteristics of carcinogens.

1-Butyl Glycidyl Ether:

This is an industrial chemical used in adhesives, sealants, and as a paint or coating additive. It is principally used to reduce the viscosity of epoxy resin systems.

1-Butyl Glycidyl Ether was added to the list (effective January 27, 2023) based on the IARC’s conclusion that the chemical is classified in Group 2B as “possibly carcinogenic to humans” based on sufficient evidence of carcinogenicity in animals and strong evidence in experimental systems that it exhibits key characteristics of carcinogens.

Glycidyl Methacrylate:

This is an ester of methacrylic acid and glycidol. Containing both an epoxide and an acrylate groups, the molecule is bifunctional. It is a common monomer used in the production of epoxy resins. It is also used in the manufacture of paints, varnishes, coatings, adhesives and sealants, fibers, thermoplastics, epoxies, and powder coatings.

Glycidyl Methacrylate was added to the list (effective January 27, 2023) based on the IARC’s conclusion that the chemical is classified in Group 2A as “probably carcinogenic to humans” based on sufficient evidence of carcinogenicity in animals, strong evidence that the chemical belongs, on the basis of mechanistic considerations, to a class of reactive glycidyl epoxides, and strong evidence in human primary cells that the chemical exhibits key characteristics of carcinogens.

Warning requirements

Although the above chemicals were listed on various dates in 2023, the warning requirement is effective one year after the date of listing. As an example, companies that sell Glycidyl Methacrylate in California must provide proper Proposition 65 warnings with all products sold on or after January 27, 2024.