California to Add Diisononyl Phthalate To Proposition 65 List of Carcinogens

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By Carolyn Whetzel

Dec. 13 --A California scientific advisory panel has cleared the way for the state's Office of Environmental Health Hazard Assessment to add a common plasticizer, diisononyl phthalate, to the list of carcinogens the agency maintains under Proposition 65, the Safe Drinking Water and Toxic Enforcement Act of 1986.

The listing will be effective Dec. 20, OEHHA said in a Dec. 12 regulatory notice.

OEHHA's Carcinogen Identification Committee considered the scientific evidence for listing diisononyl phthalate and butyl benzyl phthalate, another additive used to make materials softer and more pliable, as carcinogens under Proposition 65, at its Dec. 5 meeting in Sacramento.

The committee determined the scientific data “clearly’’ showed diisononyl phthalate could cause cancer, according to the notice. As to butyl benzyl phthalate, the committee voted against adding it to the list of carcinogens, OEHHA spokesman Sam Delson told Bloomberg BNA in a Dec. 12 e-mail.

Proposition 65 requires California to maintain a list of chemicals known to cause cancer, birth defects or reproductive toxicity. Businesses must provide clear warnings whenever exposing the public to an unsafe level of a listed substance.

OEHHA's next step will be to establish a safe exposure level for diisononyl phthalate.

Both phthalates are high production volume chemicals, meaning they are made in or imported into the U.S. in volumes of 1 million pounds or more annually, according to the U.S. Environmental Protection Agency.

Butyl benzyl phthalate (BBP) is used in polyvinyl chloride products, including flooring tiles and carpet backing, and as additive in food packaging materials, medical devices, leather coatings, paint, adhesives and inks.

Since 2009, federal and California laws have restricted the sale and distribution of toys and child care articles containing BBP concentrations of more than 0.1 percent (1,000 parts per million).

Diisononyl phthalate (DINP) is a general purpose plasticizer used in a variety of products including vinyl flooring, wire and cable insulation, stationery, coated fabrics, gloves, toys, tubing, garden hoses, footwear, automobile undercoatings and roofing materials. The phthalate ester also is found in rubbers, inks, paints, lacquers and sealants.

California law bars the sale and distribution of toys and child care products with DINP concentrations that exceed 0.1 percent.

OEHHA's advisory committee listed DINP based on animal studies showing oral exposure increased the incidence of liver tumors, islet cell tumors of the pancreas and mononuclear cell leukemia (spleen) in male and female rats; kidney tumors in male rats; testicular cell cancer in male rats; and uterine tumors in female rats.

Exxon Mobil Chemical (a division of Exxon Mobil Corp.), BASF Corp. and several industry groups submitted written comments in November opposing the listing of DINP as a carcinogen.

“Diisononyl phthalate does not meet the standard for listing under Proposition 65 as a carcinogen,” Exxon Mobil Chemical said in its comments. “The weight-of-evidence is that, while high doses of DINP cause tumors in rodents, the specific tumor types are widely known to be not relevant to human cancer assessment.”

OEHHA's hazard identification document for DINP didn't provide a balanced and complete summary of the scientific evidence, Exxon Mobil Chemical said.

The American Chemistry Council, California Manufacturers & Technology Association (CMTA), the California Building Industry Association and McKenna Long & Aldridge's San Francisco-based attorney Stanley Landfair, on behalf of BASF Corp., all submitted similar, detailed comments opposing the listing.

In his comment letter, Michael J. Rogge of CMTA said “there is a wide body of science that supports the safety of DINP and that it does not cause carcinogenic effects in humans.

“DINP has been safely used in products for decades with no known carcinogenic effects to humans,” Rogge, the group's policy director for environmental quality, said.

Tim Zacharewski, a professor at Michigan State University's Department of Biochemistry & Molecular Biology, also submitted comments saying OEHHA provided “insufficient evidence’’ to warrant the listing of DINP under Proposition 65.

To contact the reporter on this story: Carolyn Whetzel in Los Angeles at

To contact the editor responsible for this story: Larry Pearl at

OEHHA's regulatory notices are available at

The agency's hazard identification document for diisononyl phthalate is available at

The agency's scientific evidence on the carcinogenicity of butyl benzyl phthalate is available at

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