CAS No. 56-72-4
The chemical 3-chloro-7-hydroxy-4-methyl-2H-chromen-2-one/ol is a metabolite of coumaphos. First registered in 1958, coumaphos is an organophosphorus insecticide that is used to control ticks, lice, mites, and arthropod pests on beef cattle, dairy cows, swine, and certain other farm animals. Also, it has limited use in controlling mites in honeybee hives. It is not registered for uses on food crops, ornamentals, or for residential use. Coumaphos may enter the environment from spillage of animal dipping and spraying solutions (U.S.EPA, 2000). Coumaphos is generally immobile in soils and can persist for up to a year in some types of soils. It degrades to chlorferon, 6-hydroxyl-3-methylbenzofuran, and alkyl phosphates. Coumaphos is highly toxic to birds and aquatic invertebrates and moderately toxic to fish.
General population exposure to coumaphos is unlikely, though exposure through dietary meat and milk intake is possible. Estimated intakes from diet and water have not exceeded recommended intake limits (U.S.EPA, 2000). Farm and animal workers may have higher exposures as a result of absorption through dermal and inhalational routes. Once absorbed, phosphorothioates such as coumaphos are metabolically activated to the "oxon" form which has greater toxicity than the parent insecticide. Metabolic hydrolysis leads to the formation of 3-chloro-7-hydroxy-4-methyl-2H-chromen-2-one/ol, dialkyl phosphate metabolites, and other metabolites. Animal studies indicate elimination in the urine over a period of a week.
Human health effects from coumaphos at low environmental doses or at biomonitored levels from low environmental exposures are unknown. Coumaphos is considered to be an organophosphorus insecticide of moderate-to-high acute toxicity in animal studies. At high doses, coumaphos and other organophosphorus insecticides share a mechanism of toxicity: inhibition of the activity of acetylcholinesterase enzymes in the nervous system, resulting in excess acetylcholine at nerve terminals, and producing acute symptoms such as nausea, vomiting, cholinergic effects, weakness, paralysis, and seizures. Toxic effects below doses that cause inhibition of acetylcholinesterase are unknown, e.g., reproductive effects such as decrease litter size are unlikely at doses that do not inhibit acetylcholinesterase (Astroff et al., 1998). Coumaphos is not considered mutagenic and rated by the U.S.EPA as not likely to be carcinogenic in humans (U.S.EPA, 2000). Additional information about pesticides is available from U.S. EPA at https://www.epa.gov/pesticides/.
Urinary levels of 3-chloro-7-hydroxy-4-methyl-2H-chromen-2-one/ol reflect recent exposure. In the NHANES 2001-2002 subsample, most of the measurements of 3-chloro-7-hydroxy-4-methyl-2H-chromen-2-one/ol in urine were below the limit of detection, though the 95th percentile was 0.200 μg/L for the non-Hispanic black subsample (CDC, 2009). In a nonrandom study of 140 adults and children in the United States, Olsson et al. (2003) found that urinary levels of 3-chloro-7-hydroxy-4-methyl-2H-chromen-2-one/ol were below the limit of detection.
Finding a measurable amount of 3-chloro-7-hydroxy-4-methyl-2H-chromen-2-one/ol in urine does not imply that the level causes an adverse health effect. Biomonitoring studies of 3-chloro-7-hydroxy-4-methyl-2H-chromen-2-one/ol provide physicians and public health officials with reference values so that they can determine whether people have been exposed to higher levels of coumaphos than are found in the general population. Biomonitoring data can also help scientists plan and conduct research on exposure and health effects.
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