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California is opening a public debate that will ultimately determine if it will add paracetamol (known as acetaminophen in the United States) to its long list of chemicals known to cause cancer or reproductive toxicity. There are concerns this analgesic -- the world's most widely used painkiller -- might cause cancer.
Should California go ahead and classify paracetamol as a carcinogen, the effects would be most strongly felt in China, the world's largest producer of paracetamol. The United States is the world's largest market for paracetamol and California is one of the biggest local markets for this analgesic. In 2016, China accounted for 59% of the world's total production of paracetamol compared to India's 25%.
Common brand names of paracetamol sold in the United States include Tylenol and Triaminic. It's also an ingredient in other popular brands such as Excedrin, Robitussin and Theraflu. Paracetamol, which is widely used to treat mild pain and fever, has been available in the U.S. without a prescription since 1955.
The threat to the production, sales and marketing of paracetmol in California is being triggered by a state law known as Proposition 65, or the Safe Drinking Water and Toxic Enforcement Act of 1986. Under this law, California must warn people of any chemical known to cause cancer or reproductive toxicity.
The law's goals are to protect California's drinking water sources from toxic substances that cause cancer and birth defects, and to reduce or eliminate exposures to those chemicals in consumer products by requiring warnings in advance of these exposures. Proposition 65 also requires the governor revise and republish at least once a year the list of chemicals known to the State to cause cancer or reproductive toxicity. The list of substances subject to Proposition 65 comes to 900 chemicals.
A panel of scientists appointed by the governor has the authority to add chemicals to this list. In 2011, the panel voted to make acetaminophen a "high priority" candidate for the list because it believed there's enough relevant evidence to consider, said Sam Delson, spokesman for the California Office of Environmental Health Hazard Assessment.
The panel is scheduled to hold a public hearing on the listing in the spring after the public comment period closes on January 27. The process is bound to get messy.
"It's a difficult issue because it's a very commonly used drug. But that doesn't make any difference. That's not what our mandate is," said Thomas Mack, chairman of the Carcinogen Identification Committee and a professor of preventive medicine at the University of Southern California.
Supporters of Proposition 65 say the law protects Californians and consumers nationwide by forcing manufacturers to make products safer. Proposition 65 has resulted in large numbers of consumer products being reformulated to remove toxic ingredients, as proven by settlements of enforcement actions.
Evidence for acetaminophen's link to cancer is weak, however, judging from the scientific literature at hand.
The U.S. Food and Drug Administration (FDA) previously warned California officials labeling acetaminophen, as cancer causing would be "false and misleading." It will also be illegal under federal law. The International Agency for Research on Cancer (IARC), an intergovernmental agency forming part of the World Health Organization (WHO), has refused to list paracetamol as a possible carcinogen following reviews in 1990 and 1999.
