The Center for Science in the Public Interest (CSPI), a US-based nonprofit watchdog group, said Monday that both Coke and Pepsi colas contain high levels of 4-methylimidazole (4-MI), a carcinogen which forms when ammonia or ammonia and sulfites are used to manufacture the caramel coloring that gives the sodas their distinctive brown colors, according to the CSPI.
The CSPI said the National Toxicology Program (NTP), a division of the US National Institute of Environmental Health Sciences conducted animal studies concerning 4-MI. The NTP concluded that 4-MI can cause lung, liver and thyroid cancer, as well as leukemia, in laboratory mice or rats.
NTP found there is "clear evidence" that 4-MI are animal carcinogens, according to CSPI.
The CSPI found that in Washington-area stores, Pepsi's products had 145 and 153 micrograms (mcg) of 4-MI in two 12-ounce cans. Regular Coke had 142 mcg per 12 ounces in one sample and 146 mcg in another. Diet Coke had 103 mcg per 12 ounces in one sample and 113 mcg in another.
The state of California requires warning labels on any foods or beverages containing more than 29 mcg of 4-MI - a limit far lower than the levels found in Coke and Pepsi products.
The CSPI estimated that the 4-MI in Coke and Pepsi is responsible for thousands of cancer cases in the US every year.
US Regulators Say 4-MI Within Safety Limit
The US Food and Drug Administration's (FDA) limit for 4-MI in caramel coloring is 250 parts per million (PPM), which is 1,000 times more than the amount the CSPI found in Coke and Pepsi products.
The FDA, citing the results of giving 4-MI to mice, said that 1,000 cans of Coke or Pepsi would be required to reach the amount needed to cause cancer in mice.
In accordance with the FDA's standpoint, the American Beverage Association argued that there is no experiment confirming that 4-MI can cause cancer in human beings.
Deng Jou-Fang, administrative officer of Taipei Veterans General Hospital, stated that the result of animal experiments cannot be directly applied to human beings.
Since the population drinking Coke or Pepsi is so large and people have been drinking the beverages for so long, an epidemiological study can easily confirm whether there is any causality between drinking the colas and having cancer, Deng said.