The Truth About Organic Foods

The calculations outlined in the “Acute Toxicity” sidebar contained an error in presenting LD50 doses as body weight, thereby overestimating the equivalent human body weight doses. Below is the corrected text. I apologize for this error and have brought it to your attention as quickly and transparently as possible.

Alex Avery

Corrected text:

There are two types of toxicity: chronic and acute. Chronic toxicity refers to health problems caused by long-term exposures to low doses of a substance. Acute toxicity is the immediate impact of a high dose of a chemical or substance.

One way that acute toxicity is measured is the Lethal Dose 50% (LD50), the dose that kills half of the population of a test organism. The lower the LD50, the more toxic the substance.

Thiabendazole has an oral LD50 (if ingested by mouth) in rats of 3,100 to 3,600 milligrams per kilogram (mg/kg). There are 1,000,000 milligrams in a kilogram, so this is a 0.3 to 0.36 percent of body weight dose. In mice, the LD50 is 1,400 to 3,800 mg/kg, or 0.14 to 0.38 percent of body weight. Using the conservative 0.14 percent LD50 from mice, this works out to nearly a quarter pound (0.217 lbs) of pure thiabendazole for a 155 lb human male (equivalent to 100 grams in a 70 kilogram adult). Even if thiabendazole were toxic at half that dose, the 0.4 mg of thiabendazole in the pessimistically contaminated theoretical pound of apples is still less than 0.01 percent of an acutely toxic dose (1/11,250^th). And even at high doses there aren’t any long-term (chronic) toxicity concerns with thiabendazole, such as cancer.

For comparison, the organic insecticide pyrethrum has a mammalian LD50 ranging from 200 to 2,600 mg/kg. The minimum lethal dose in humans (yes, it has killed humans) is 750 mg/kg in children. Thus, organic pyrethrum is over twice as acutely toxic as thiabendazole.

The organic fungicide copper sulfate has a mammalian LD50 of 30 mg/kg, making copper sulfate at least 45 times more acutely toxic than thiabendazole.