Natural toxicants in human foods: psoralens in raw and cooked parsnip root.

Parsnip root contains three photoactive, mutagenic, and photocarcinogenic psoralens in a total concentration of about 40 parts per million. These chemicals are not destroyed by normal cooking procedures (boiling or microwave); thus humans are exposed to appreciable levels of psoralens through the consumption of parsnip and possibly other psoralen-containing foodstuffs. The toxicologic consequences to man of such exposure may be speculated on the basis of medicinal and laboratory studies, but epidemiologic data are not available.