3-MCPD (3-monochloropropane-1,2-diol or 3-chloropropane-1,2-diol) is an organic chemical compound which is the most common member of chemical food contaminants known as chloropropanols. It is suspected to be carcinogenic in humans.
3-Monochloropropane-1,2-diol; α-Chlorohydrin; Glycerol α-monochlorohydrin; Chlorodeoxyglycerol; 3-Chloro-1,2-propanediol
3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||110.54 g·mol−1|
|Appearance||Viscous, colorless liquid|
|Melting point||−40 °C (−40 °F; 233 K)|
|Boiling point||213 °C (415 °F; 486 K)|
|Safety data sheet||External MSDS|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
It is primarily created in foods during protein hydrolysis when hydrochloric acid is added at high temperature to speed up the breakdown of proteins into amino acids. As a byproduct of this process, chloride can react with the glycerol backbone of lipids to produce 3-MCPD. 3-MCPD can also occur in foods which have been in contact with materials containing epichlorohydrin-based wet-strength resins which are used in the production of some tea bags and sausage casings.
In 2009, 3-MCPD was found in some East Asian and Southeast Asian sauces such as oyster sauce, Hoisin sauce, and soy sauce. Using hydrochloric acid rather than traditional slow fermentation is a far cheaper and faster method but unavoidably creates chloropropanols. A 2013 European Food Safety Authority report indicated margarine, vegetable oils (excluding walnut oil), preserved meats, bread, and fine bakery wares as major sources in Europe.
Absorption and toxicity
The International Agency for Research on Cancer has classified 3-MCPD as Group 2B, "possibly carcinogenic to humans". 3-MCPD is carcinogenic in rodents via a non-genotoxic mechanism. It is able to cross the blood-testis barrier and blood–brain barrier. The oral LD50 of 3-chloro-1,2-propanediol is 152 mg/kg bodyweight in rats.
3-MCPD also has male antifertility effects and can be used as a rat chemosterilant.
The joint Food Standards Australia New Zealand (FSANZ) set a limit for 3-MCPD in soy sauce of 0.02 mg/kg, in line with European Commission standards which came into force in the EU in April 2002.
In 2000, a survey of soy sauces and similar products available in the UK was carried out by the Joint Ministry of Agriculture, Fisheries and Food/Department of Health Food Safety and Standards Group (JFSSG) and reported more than half of the samples collected from retail outlets contained various levels of 3-MCPD.
In 2001, the United Kingdom Food Standards Agency (FSA) found in tests of various oyster sauces and soy sauces that 22% of samples contained 3-MCPD at levels considerably higher than those deemed safe by the European Union. About two-thirds of these samples also contained a second chloropropanol called 1,3-dichloropropane-2-ol (1,3-DCP) which experts advise should not be present at any levels in food. Both chemicals have the potential to cause cancer and the Agency recommended that the affected products be withdrawn from shelves and avoided.
In 2001 the FSA and Food Standards Australia New Zealand (FSANZ) singled out brands and products imported from Thailand, China, Hong Kong, and Taiwan. Brands named in the British warning include Golden Mountain, King Imperial, Pearl River Bridge, Golden Mark, Kimlan, Golden Swan, Sinsin, Tung Chun, and Wanjasham soy sauce. Knorr soy sauce was also implicated, as well as Uni-President Enterprises Corporation creamy soy sauce from Taiwan, Silver Swan soy sauce from the Philippines, Ta Tun soy bean sauce from Taiwan, Tau Vi Yeu seasoning sauce and Soya bean sauce from Vietnam, Zu Miao Fo Shan soy superior sauce and Mushroom soy sauce from China and Golden Mountain and Lee Kum Kee chicken marinade. Between 2002 and 2004, relatively high levels of 3-MCPD and other chloropropanols were found in soy sauce and other foods in China.
In 2007 in Vietnam, 3-MCPD was found in toxic levels. In 2004, the HCM City Institute of Hygiene and Public Health found 33 of 41 sample of soy sauce with high rates of 3-MCPD, including six samples with up to 11,000 to 18,000 times more 3-MPCD than permitted, an increase over 23 to 5,644 times in 2001, The newspaper Thanh Nien Daily commented, "Health agencies have known that Vietnamese soy sauce, the country's second most popular sauce after fish sauce, has been chock full of cancer agents since at least 2001."
In November 2008, Britain's Food Standards Agency reported a wide range of household name food products from sliced bread to crackers, beefburgers and cheese with 3-MCPD above safe limits. Relatively high levels of the chemical were found in popular brands such as Mother's Pride, Jacobs crackers, John West, Kraft Dairylea and McVitie's Krackawheat. The same study also found relatively high levels in a range of supermarket own-brands, including Tesco char-grilled beefburgers, Sainsbury's Hot 'n Spicy Chicken Drumsticks and digestive biscuits from Asda. The highest levels of 3-MCPD found in a non- soy sauce product, crackers, was 134 µg per kg. The highest level of 3-MCPD found in soy sauce was 93,000 µg per kg, 700 times higher. The legal limit for 3-MCPD coming in next year will be 20 µg per kg, but the safety guideline on daily intake is 120 µg for a 60 kg person per day.
In 2016 the occurrence of 3-MCPD in selected paper products (coffee filters, tea bags, disposable paper hot beverage cups, milk paperboard containers, paper towels) sold on the Canadian and German market was reported and the transfer of 3-MCPD from those products to beverages was investigated. Exposure to 3-MCPD from packaging material would likely constitute only a small percentage of overall dietary exposure when compared to the intake of processed oils/fats containing 3-MCPD equivalent (in form of fatty acid esters) which are often present at levels of about 0.2-2 µg/g.
Some companies such as MASAN in Vietnam continue to use the rapid soy protein hydrolyzation method, but modify methods by adding special additives that have origin from China, to lower or even reduce these contaminants to levels not detected by standard testing methods. Hydrolyzing with hydrochloric acid always produces some 3-MCPD, but for 1,3-DCP, a byproduct of 3-MCPD, there is no standard as it is unregulated yet. This problem is controversial among food safety experts
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