4-Methylimidazole in Cola Drinks


  1. In March 2012, a U.S. policy advocacy organisation found that 4-methylimidazole (4-MI), a chemical contaminant arisen from the formation of some caramel colourings, was present in cola drinks available in the U.S. market.
  2. Caramels are dark brown to black liquids or solids having an odour of burnt sugar. They can be used as food colour in a wide variety of foods, such as giving the distinctive brown colour to cola drinks.
  3. Caramel colourings are divided into four classes, namely Caramel I, II, III and IV with respective International Numbering System (INS) * number 150a, 150b, 150c and 150d. 4-MI is a contaminant in Caramel III and IV the manufacturing process of which involves the presence of ammonium compounds.

Safety and Public Health Significance

  1. The safety of 4-MI in food has raised concern because of its cancer-causing potential. The International Agency for Research on Cancer (IARC) has evaluated the carcinogenicity of 4-MI and considered 4-MI as "possibly carcinogenic to humans" (i.e. Group 2B) solely basing on the studies in animals.
  2. Joint FAO/WHO Expert Committee on Food Additives (JECFA) has not evaluated the safety of 4-MI. Nevertheless, during its evaluation on caramel colourings, JECFA opined that the acute neurological effects produced by high doses of 4-MI would not appear to be of major concern when caramel colourings containing small amounts of this contaminant are used in food.
  3. The European Food Safety Authority (EFSA) has also evaluated the safety of caramel colourings and concluded that they are neither genotoxic (i.e. capable to cause damage to DNA), nor carcinogenic and that there is no evidence to show that they have any adverse effects on human reproduction or for the developing child. EFSA also considered that the highest exposure level to 4-MI that could result from the consumption of foods containing Caramel III and IV did not give rise to concern.
  4. Based on the highest detected level of 4-MI in cola drinks (i.e. 153 micrograms per 12 fl. oz. or about 360 mL) as reported by a U.S. policy advocacy organisation, a 60-kg individual would have to consume over 300 cans of that cola drink a day to reach the doses causing cancer in rodents after applying an uncertainty factor of 100.

Regulatory Control

  1. The Codex Alimentarius Commission has set provisions for the use of caramel colourings in a wide variety of food commodities. In Hong Kong, caramel is a permitted colouring matter under the Colouring Matters in Food Regulations.
  2. JECFA has set the maximum levels of 4-MI in Caramel III and IV in their chemical specifications to indicate good manufacturing practice. Some countries including the European Union, Mainland China and Korea have also set maximum level of 4-MI in Caramel III and IV.
  3. In the U.S., as stipulated in the Code of Federal Regulation, caramel colourings may be safely used for colouring foods generally, in amounts consistent with good manufacturing practice. Yet maximum level of 4-MI is not specified. However, in the U.S. State of California, 4-MI is a listed chemical known to cause cancer, effective since January 2011. Businesses are required to provide a "clear and reasonable" warning before knowingly and intentionally exposing anyone to a listed chemical.

Advice to Public

  1. Maintain a balanced diet so as to avoid excessive exposure to food additives and contaminants from a small range of food items.
  2. Usual consumption of Cola drinks is not likely leading to adverse health effects arising from exposure to 4-MI.
  3. For concerned individuals, they can read food label on prepackaged food and look for Caramel III and IV or their identification numbers (150c, 150d) so as to make informed choices.

Advice to Trade

  1. Manufacturers of caramel colourings should maintain the levels of 4-MI as low as technically possible through appropriate process control (e.g. variations in temperature, pressure and ingredients etc).
  2. Food manufacturers should use food colourings with the lowest possible level required for the intended colouring function.
  3. Ensure that all food products for sale comply with local regulations, including food additive and labelling requirements.

* International Numbering System (INS) for Food Additives is adopted by the Codex Alimentarius Commission, which provides internationally agreed identification numbers for food additives.

Risk Assessment Section
Centre for Food Safety
April 2012