In another safety scare for China’s dairy industry, a random inspection of milk products from the country’s largest dairy manufacturer by the Chinese government watchdog group were found to contain excessive aflatoxin M1, a carcinogen, reports Beijing Times.  It was reported that the milk products had aflatoxin M1 levels that were 140 percent higher than the permitted levels. The maximum allowable limit of aflatoxin M1 is 0.5 µg/kg, while the contaminated milk products contained 1.2 µg/kg of aflatoxin M1.

Aflatoxins can be found in milk after cows consume feed contaminated by mould and can increase the risk of cancer, including liver cancer. Aflatoxin M1 cannot be killed by pasteurization. Dairy expert, Wang Dingmian, said excessive amounts of aflatoxin M1 could accumulate in the body and trigger cancer in both animals and humans.  If the milk cows were fed with fresh grass, the problem might not have occurred. The toxin would disappear from the milk if the animals stop eating the rotten feed.

Aflatoxin M1 contamination of milk results primarily from the conversion of aflatoxin B1 that is metabolized by enzymes found primarily in the liver. After aflatoxin M1 is formed, it is excreted in the urine and milk of the cow.  Aflatoxins produce acute necrosis, cirrhosis, and carcinoma of the liver in a number of animal species; no animal species is resistant to the acute toxic effects of aflatoxins.

The World Health Organization (WHO) classified aflatoxins as Group 1 carcinogens. Aflatoxins are acutely toxic, immunosuppressive, mutagenic, teratogenic and carcinogenic compounds. The main target organ for toxicity and carcinogenicity is the liver. Aflatoxins have been detected in the blood of pregnant women, in neonatal umbilical cord blood, and in breast milk.

Aflatoxins are considered unavoidable contaminants of food and feed, even where good manufacturing practices have been followed. As both aflatoxins B1 and M1 may cause cancer in humans, the action level of 0.5 parts per billion (ppb) of aflatoxin M1 in milk is regulated by the United States Food and Drug Administration (FDA). However, it is very difficult to accurately estimate aflatoxins concentrations in a large quantity of material because of the variability associated with testing procedures; the true aflatoxin concentration in a lot cannot be determined with 100% certainty.

The results of the numerous studies on the effect of milk processing on the concentration of aflatoxin M1 are variable. The concentration is not appreciably reduced by heat treatment. Production of yoghurt, cheese, cream, milk powder, or butter does not lead to loss of aflatoxin M1, although it is redistributed differentially into the products resulting from these processes. Aflatoxin M1 can be partially eliminated from milk by physical or chemical procedures, which include use of adsorbents, hydrogen peroxide, and ultra-violet radiation. These treatments are not readily applicable for the dairy industry, however, and their safety has not been tested; moreover, the costs may be prohibitive for large-scale application.

This latest food safety report in China follows a report earlier this month, when a Chinese court sentenced a woman to death and jailed her husband for life for lacing milk sold by a competitor with the industrial salt nitrite as a form of revenge, killing three children and making 36 sick.

Reference:  Safety evaluation of certain contaminants in food / prepared by the Seventy-second meeting of the Joint FAO/WHO Expert Committee on Food Additives (JECFA), May 26, 2011