The State of California is debating whether to list acetaminophen, a common ingredient found in prescriptions and over-the-counter drugs like Vicodin and Tylenol, as a carcinogen on the Proposition 65 list. 

Acetaminophen was linked to cancer in a peer-reviewed study published in the Journal of Clinical Oncology in 2011. The study examined approximately 65,000 adults aged 50-76, and found an increased risk, as high as two-fold, of blood cancer in patients that reported using acetaminophen regularly.

Prop. 65 is a California law passed in 1986 that requires the State to publish a list of chemicals known to cause cancer, birth defects and other reproductive harm, as dictated by the California Office of Environmental Health Hazard Assessment. This list is updated at least once a year, and has grown to include approximately 900 chemicals. 

The law requires businesses in California to provide warnings to consumers about the excessive or extended use of these chemicals in products. Prop. 65 is designed to inform Californians about the products they are using, and allows consumers to make informed decisions, while also encouraging companies to produce safer products.

After allowing a lengthy period for public comment, the Carcinogen Identification Committee will review the drug this week, and the State will decide this spring whether to officially list acetaminophen as a known carcinogen.

The American Liver Foundation states that acetaminophen is the most common ingredient found in drugs in the U.S.  The medicine is found in over 600 products, and is commonly used for the treatment of pain, fever, colds and allergies. It can be prescribed and sold over the counter, and is widely approved for children and adults.

As the most populous state in the nation, California is a major market for the pharmaceutical industry. Manufacturers are well-aware of the financial implications resulting from being placed on the Prop 65 list, and public relations teams are working overtime to prevent the occurrence. 

According to ABC News, there are 133 studies on acetaminophen that have been published in peer-reviewed journals. Some of these studies found an increased risk of developing  kidney, liver, and blood cancer, yet other studies found no correlation. ABC News reported that, “overall, the review noted acetaminophen has been difficult to examine because it is hard to isolate it from other variables that could contribute to cancer, such as smoking.”