At high enough exposure levels, aflatoxins can cause acute toxicity, and potentially death, in mammals, birds and fish, as well as in humans. The liver is the principal organ affected, but high levels of aflatoxin have also been found in the lungs, kidneys, brains and hearts of individuals dying of acute aflatoxicosis. Acute necrosis and cirrhosis of the liver is typical, along with haemorrhaging and oedema. LD50 (lethal dose) values for animals vary between 0.5 and 10 mg/kg body weight.
Chronic toxicity is probably more important from a food safety point of view, certainly in more developed regions of the world. Aflatoxin B1 is a very potent carcinogen and a mutagen in many animals, and therefore potentially in humans, and the liver is again the main target organ. Ingestion of low levels over a long period has been implicated in primary liver cancer, chronic hepatitis, jaundice, cirrhosis and impaired nutrient conversion. Aflatoxins may also play a role in other conditions, such as Reye’s syndrome and kwashiorkor (a childhood condition linked to malnutrition). Less is known about the chronic toxicity of aflatoxin G1 and M1, but these are also thought to be carcinogens, though probably a little less potent than B1.
Little is known about the level of dietary exposure to aflatoxins necessary to affect health, especially in humans, and diagnosis of chronic toxicity is very difficult. It is generally agreed that the best approach is to minimise the levels in all foods as far as is technically possible and to assume that any dietary exposure is undesirable.