Aflatoxin B1 is an aflatoxin produced by Aspergillus flavus and A. parasiticus. Aflatoxin B1 is a very potent carcinogen with a TD₅₀ 0.0032 mg/kg/day in rats. This carcinogenic potency varies across species with some, such as rats and monkeys, seemingly much more susceptible than others. It is a common contaminant in a variety of foods including peanuts, cottonseed meal, corn, and other grains; as well as animal feeds.