Aflatoxins in Edible Oils and Fats




  • Most aflatoxin contamination in edible oils and fats is caused by Aspergillus flavus in the process of oil cultivation, harvesting, transportation and storage, especially in hot and humid environments.
  • Aflatoxin B1 is the most common of the known aflatoxins, and its toxicity and carcinogenicity are the strongest. Cases of acute toxicity from aflatoxins are uncommon. It is mainly harmful to human health through long-term accumulation of the toxin, which may lead to liver cirrhosis, tumours, teratogenic and other genetic effects.
  • Aflatoxins are highly heat-resistant and cannot be decomposed or completely eliminated by normal cooking and heating processes.
  • The Regulamento Administrativo n.º 13/2016 “Limites máximos de micotoxinas em alimentos” (Maximum Limits of Mycotoxins in Food), which has been promulgated and is in force in Macao, sets maximum limits for aflatoxin B1 in edible oils and fats.
  • The trade and the public are advised to purchase hygienic and good quality edible oils and fats from reputable suppliers or shops and avoid storing them in hot and humid environments.




Aflatoxins are one of the most common mycotoxins that contaminate crops and their products. It is also sometimes detected in peanuts, corn, cereals and other nuts, among which the contamination of grain and oil products from peanuts and corn is of greater concern. Edible oils and fats are commonly used as raw food materials for cooking. If the oil is not strictly controlled during the cultivation, harvesting, transportation and storage processes, or if it is exposed to high temperature and humidity for a long period of time, there is a risk of mould infestation and aflatoxin production. The consumption of aflatoxin-contaminated edible oils and fats may pose risks to human health.


Aflatoxins and Their Consumption Risks


Aflatoxins are the secondary metabolites produced by Aspergillus flavus and Aspergillus parasiticus. The toxicity of aflatoxins, which mainly include aflatoxin B1, B2, G1 and G2, varies greatly depending on their type or structure. Among them, aflatoxin B1 is the most common, the most toxic and the most potent in terms of causing liver cancer.


According to the research reports of the International Agency for Research on Cancer (IARC) of the World Health Organization, there is sufficient evidence that aflatoxins are carcinogenic in humans and animals, and that they induce embryonic malformations and pose damaging effects on hepatic tissue in humans and animals. In addition, the ingestion of aflatoxins reduces the immunity of humans and animals, causing nutritional disorders and other adverse effects, and may cause acute and chronic toxicity (mainly liver damage) and even death. Therefore, aflatoxins are classified as carcinogens to humans (Group 1).


Despite the high toxicity of aflatoxins, cases of acute toxicity from aflatoxins are rare due to extremely low levels of aflatoxins in crops and their products. According to previous epidemiological studies, the incidence of acute toxicity of aflatoxins under normal dietary conditions is extremely low. Rather, adverse effects mainly caused by chronic dietary exposure to aflatoxins are more frequently seen. Acute toxicity of aflatoxins may have symptoms including fever, vomiting and jaundice, and may also lead to acute liver damage which may be fatal in severe cases. Moreover, it is worth noting that aflatoxins are highly heat-resistant, so normal cooking and heating processes cannot decompose or completely eliminate them, and human exposure to aflatoxins is principally through the consumption of contaminated food.


Regulatory Measures and Surveillance Results


According to Lei n.º 5/2013 “Lei de segurança alimentar” (Food Safety Law) of Macao, the trade is responsible for ensuring that the food supplies are hygienic, suitable and safe for human consumption. Meanwhile, the food and its raw materials must be sold in accordance with a range of food safety standards that have been promulgated and are in force in Macao.


At present, the relevant standards on mycotoxins promulgated and in force in Macao include the Regulamento Administrativo n.º 13/2016 “Limites máximos de micotoxinas em alimentos” (Maximum Limits of Mycotoxins in Food), which sets maximum limits for aflatoxin B1 in “peanut oil and corn oil”, and “vegetable oils and fats other than peanut oil and corn oil” respectively.


The Municipal Affairs Bureau (IAM) continuously monitors the food safety of the food products sold on the market by carrying out targeted food surveillance. In 2022, IAM tested 100 edible vegetable oils and fats for aflatoxin B1 and no abnormal results were found. In the case where a sample exceeds the relevant standards in Macao, a food alert will be issued to the trade if necessary, directing an immediate recall of the related food product.


Advice for the Trade and the Public


  • Purchase edible oils and fats of good hygiene and quality from reputable suppliers or shops;
  • Avoid storing edible oils and fats in hot and humid places, and avoid prolonged exposure to light or high temperatures such as sunlight, near ovens or cooking stoves, which may accelerate oxidation and deterioration;
  • Purchase food in the amount according to your daily needs, such as buying small packages to ensure the freshness of edible oils and fats, or dividing large packages into small bottles, and consume it as soon as possible;
  • Considering that the smoke point and usage of each kind of edible oils and fats are different, it is recommended to choose appropriate ones according to the cooking method, such as olive oil and flaxseed oil for cold dish; sunflower oil, soybean oil, peanut oil, corn oil for pan-frying, boiling and sautéing; and lard, butter, palm oil for stir-frying or deep-frying;
  • Do not buy, sell or supply food products if there is any doubt as to their origin, hygiene and quality. In addition, the trade is obliged to keep records or relevant receipts on the purchase and sales of food products, so as to protect their own interests, and offer the competent authorities with such proof to trace the source and flow of food products whenever necessary.



1.       Regulamento Administrativo n.º 13/2016 “Limites máximos de micotoxinas em alimentos” (Maximum Limits of Mycotoxins in Food)


2.       Aflatoxins in Food (Hong Kong Centre for Food Safety). 8 October 2018


3.       Chemical Hazards Evaluation - Aflatoxin in Foods (Hong Kong Centre for Food Safety). 17 August 2017


4.      Identification and Prevention of Aflatoxin Contamination in Agricultural Products and Food (Ministry of Agriculture and Rural Affairs of the People’s Republic of China). 27 November 2020


5.       What We Should Know About Aflatoxin (Municipal Affairs Bureau). 1 January 2019


6.       Risk assessment of aflatoxins in food (European Food Safety Authority). 9 March 2020


7.       Aflatoxins and Food Safety (Singapore Food Agency). 28 April 2022


8.       Aflatoxins (National Cancer Institute). 05 December 2022


BRR 003 DAR 2023