We know there is an ever-growing list of everyday items that can increase the risk of cancer. Some are no-brainers – smoking, unprotected and prolonged exposure to the sun, and red meat, to name a few – but what about … acetaminophen? Can Tylenol cause cancer?
California’s “Safe Drinking Water and Toxic Enforcement Act of 1986,” also known as Proposition 65, requires the state to keep a list of chemicals “known to the state to cause cancer or reproductive toxicity.” (Fun fact: There are more than 900 chemicals on the list.) (1)
And yes, acetaminophen is up for discussion during the upcoming public hearing. For what it’s worth, Tylenol isn’t the only over-the-counter medications that contain acetaminophen. Most likely, you’ve used a few of these: Actifed, Dayquil, Dimetapp, Excedrin, Midol, Nyquil, Sudafed, Theraflu, Vicks, and Zicam, among many others. (2)
Exposure to acetaminophen mainly comes from the use of OTC and prescription medications by the oral, intravenous injection, and rectal routes. According to the Acetaminophen Awareness Coalition, 50 million Americans use medicines containing acetaminophen each week.
So how did acetaminophen enter the cancer fray?
While relatively rare, there are potential risks and complications associated with acetaminophen. The U.S. Food and Drug Administration advises that the maximum safe daily dose for acetaminophen is 4000 mg for adults. Overdose, which can lead to liver failure, is the most significant risk associated with acetaminophen. (3)
An overdose is severe and can be fatal. Signs of an acetaminophen overdose include:
- Nausea and vomiting
- Abdominal pain, particularly on the right side
- Loss of appetite
Anyone who shows signs of an overdose needs immediate medical attention. Because acetaminophen is processed in the liver, some people with liver problems may be more susceptible to overdose.
Several human epidemiological studies, however, have probed the relationship between acetaminophen and various diseases, including kidney cancer, urinary bladder cancer, urinary tract cancers, lymph system cancers, and liver cancer. Furthermore, long-term carcinogenicity studies of acetaminophen have been conducted in mice and rats. Significant tumor findings were observed in three of 10 studies in mice and in three of seven studies in rats. (3)
Because of its extensive use, acetaminophen is commonly detected in septic tank discharge and wastewater. Acetaminophen has been detected in groundwater, surface water, seawater, and soil and sediment. It also has been found in wildlife – e.g., fish and osprey nestlings.
Also, in utero exposure and exposure via breastmilk from maternal use of acetaminophen occurs; it crosses the placenta and is excreted in breast milk. There also is the potential for occupational exposure during production and use in the manufacturing of other chemicals. In 1999, it was estimated that 65,000 U.S. workers were potentially exposed to acetaminophen.
Concerns over the carcinogenicity of acetaminophen arose because it is the major metabolite of phenacetin, a recognized carcinogen that causes cancer of the renal pelvis. Acetaminophen was evaluated for its carcinogenicity in 1990 and 1999 and classified in Group 3 (not classifiable as to its carcinogenicity to humans). The epidemiologic data on carcinogenicity were determined to be inadequate or inconsistent by the target organ.
Several cohort and case-control studies examining the association of cancers at various sites with acetaminophen exposure have been published since the IARC review. Two overlapping meta-analyses published since the 1999 IARC evaluation included several case-control studies, as well as cohort studies, and reported an increased risk of kidney cancer associated with the use of acetaminophen. (4, 5)
The Consumer Healthcare Products Association represents over-the-counter medicine manufacturers. The CHPA issued a statement that said in part: “In order to be listed under Prop 65 in California, acetaminophen must be ‘clearly shown through scientifically valid testing according to generally accepted principles’ to cause cancer. An up-to-date review of the scientific evidence based on input from leading experts in the fields of epidemiology, genotoxicity, and animal carcinogenicity found that the weight of the scientific evidence clearly demonstrates there is no causal association between acetaminophen use and cancer.”
Clearly more research is needed to draw a direct line between acetaminophen and cancer. Now is not the time to question your OTC meds! Meanwhile, if you have to take medications that contains acetaminophen, discuss with a doctor the correct dosage based on your specific health needs.
(1) The Proposition 65 List. https://oehha.ca.gov/proposition-65/proposition-65-list
(2) Evidence on the Carcinogenicity of Acetaminophen. https://oehha.ca.gov/media/downloads/crnr/acetaminophenhid092019.pdf
(3) Prescription Drug Products Containing Acetaminophen: Actions to Reduce Liver Injury from Unintentional Overdose. https://www.regulations.gov/document?D=FDA-2011-N-0021-0001
(4) Analgesic use and the risk of kidney cancer: a meta-analysis of epidemiologic studies. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3815746/
(5) Analgesic use and risk of renal cell carcinoma: A case-control, cohort and meta-analytic assessment. https://www.ncbi.nlm.nih.gov/pubmed/27009534