Toxicity and use in foods, beverages, tobacco, and cosmetics
Coumarin is moderately toxic to the liver and kidneys, with a "Median Lethal Dose" (LD50) of 275 mg/kg — low compared to related compounds. Although only somewhat dangerous to humans, coumarin is a potent rodenticide: Rats and other rodents metabolize it largely to 3,4-coumarin epoxide, a toxic compound that can cause internal hemorrhage and death. Humans metabolize it largely to 7-hydroxycoumarin, a compound of lower toxicity. The German Federal Institute for Risk Assessment has established a "tolerable daily intake" (TDI) of 0.1 mg coumarin per kg body weight, but also advises, [if] this level is exceeded for a short time only, there is no threat to health.[11] For example, a person weighing 60 kg (about 132 lbs) would have a TDI of approximately 6.0 mg of coumarin.
European health agencies have warned against consuming high amounts of cassia bark, one of the four species of cinnamon, because of its coumarin content.[12] According to the German Federal Institute for Risk Assessment, 1 kg of (cassia) cinnamon powder contains approximately 2.1 to 4.4 g of coumarin.[13] Powdered Cassia Cinnamon weighs 0.56 g/cc;[14] therefore, 1 kg of Cassia Cinnamon powder is equal to 362.29 teaspoons (1000 g divided by 0.56 g/cc multiplied by 0.20288 tsp/cc). This means 1 teaspoon of cinnamon powder contains 5.8 to 12.1 mg of coumarin, which may be above the Tolerable Daily Intake for smaller individuals.[13] However, it is important to note that the German Federal Institute for Risk Assessment only cautions against high daily intakes of foods containing coumarin. Chamomile, a common herbal tea, also contains coumarin.
Coumarin is often found in tobacco products and artificial vanilla substitutes, despite having been banned as a food additive in numerous countries since the mid-20th century. Coumarin was banned as a food additive in the United States in 1954, largely because of hepatotoxicity results in rodents.[15] OSHA considers this compound to be only a lung-specific carcinogen, and "not classifiable as to its carcinogenicity to humans".[16] Coumarin was banned as an adulterant in cigarettes by tobacco companies in 1997, but due to the lack of reporting requirements to the US Department of Health and Human Services it was still being used as a flavoring additive in pipe tobacco.[citation needed] Coumarin is currently listed by the United States Food and Drug Administration (FDA) among "Substances Generally Prohibited From Direct Addition or Use as Human Food", according to 21 CFR 189.130,[17][18] but some natural additives containing coumarin, such as sweet woodruff (Galium odoratum) due to its coumarin odor, are allowed "in alcoholic beverages only" (21 CFR 172.510).[19] In Europe, such beverages are very popular, for example Maiwein (white wine with woodruff) and Żubrówka (vodka flavoured with bison grass). However, the coumarin content of these drinks is said to cause headaches.
Coumarin should be avoided by people with perfume allergy.[20]
