A lawsuit brought by environmental advocates in California claims that leading brands of fish oil dietary supplements contain unsafe and illegal levels of the carcinogenic chemicals known as polychlorinated biphenyls, or PCBs, which were banned back in 1979.

Filed in California Superior Court in San Francisco, the lawsuit accuses eight supplement manufacturers or distributors for alleged violations of California's Proposition 65, which requires that consumers be warned about chemical exposures. The supplement makers named in the lawsuit are CVS Pharmacy, Rite Aid, General Nutrition Corp., Solgar, Twinlab, Now Health, Omega Protein and Pharmavite.

The suit was filed by Attorney David Roe, contending Proposition 65, a law he helped write, requiring consumers to be warned when products contain toxic ingredients above the limit deemed safe by regulators.

Manufacturers of the supplements contest the results of the tests, saying their products are safe.

Twinlab's chief science officer, Greg Grochoski, said the two Twinlab Norwegian cod liver oils tested are distilled to reduce impurities such as PCBs and meet government standards.

Issued by the California plaintiffs, added spokesman Justin Boone, noting that Twinlab products were reported as having among the lowest levels of impurities. "Twinlab cannot comment on the validity or accuracy of the test results referenced in a press release".