What Is 4-MEI?
The FDA says 4-methylimidazole, or 4-MEI, forms as a byproduct at low levels in some foods and beverages during normal cooking, such as roasting coffee beans or roasting and grilling meats, and also forms when certain caramel colorings, known as Class III and Class IV, are made. It says foods labeled with caramel coloring do not necessarily contain 4-MEI, because Class I and Class II caramel coloring do not contain it.
The FDA says 2007 National Toxicology Program studies found a 2-year rat study inconclusive on cancer, while a 2-year mouse study showed more of certain lung tumors, at 4-MEI levels far above estimated human exposure from food. It says its review will help decide what regulatory action, if any, is needed, which could include a limit on 4-MEI in Class III and IV caramel coloring, and that in the meantime it is not recommending that consumers change their diets because of 4-MEI.
California acted under Proposition 65. OEHHA listed 4-methylimidazole as a chemical known to the state to cause cancer effective January 7, 2011, and its no significant risk level, effective February 8, 2012, says no warning is required for exposures at or below 29 micrograms per day.
Sources checked September 15, 2026. Every point below links the page it came from.
The sources behind this answer
- Government sourceThe FDA says 4-MEI forms at low levels during normal cooking, such as roasting coffee beans or grilling meats, and during manufacture of Class III and Class IV caramel coloring. US FDA ↗
- Government sourceThe FDA says foods labeled with caramel coloring do not necessarily contain 4-MEI, because Class I and Class II caramel coloring do not contain it. US FDA ↗
- StudyThe FDA says 2007 NTP studies found a 2-year rat study inconclusive on carcinogenicity and a mouse study with more lung tumors, at 4-MEI levels far exceeding estimated human exposure from food. US FDA ↗
- Government sourceThe FDA says its review may lead to a limit on 4-MEI in Class III and IV caramel coloring, and in the interim it is not recommending that consumers change their diets because of 4-MEI. US FDA ↗
- Regulatory filingCalifornia OEHHA listed 4-methylimidazole as a chemical known to the state to cause cancer under Proposition 65, effective January 7, 2011. California OEHHA, via web.archive.org ↗
- Regulatory filingOEHHA's no significant risk level for 4-MEI, effective February 8, 2012, says no warning is required for exposures at or below 29 micrograms per day. California OEHHA, via web.archive.org ↗
Sources checked September 15, 2026. A brand statement is the company’s own claim, which we report but have not verified. Our grades are model-based estimates, not lab tests.