Introduction to Endocrine Disrupting Chemicals

ii. Chlorpyrifos
Where it is used
Organophosphorus pesticides (OPs) are some of the most commonly used insecticides
worldwide, and chlorpyrifos is a typical OP. It is used to control household
pests such as cockroaches, flies, termites, fire ants, mosquitoes, and lice. Chlorpyrifos
is used agriculturally to combat pests on cotton, grain, seed, nut, fruit, wine,
and vegetable crops. It is also used in forestry, nurseries, food processing plants,
on golf courses, and in water supplies to combat larvae, especially mosquitoes. It
has numerous other uses, such as impregnated bags to cover ripening bananas in
plantations, in cattle ear tags, and in paint. It is acutely toxic to some species that
are beneficial to agriculture, such as earthworms and honeybees.
Where people are exposed, and where risks are
Relative to organochlorine pesticides, chlorpyrifos degrades more rapidly in the
environment. However, it can still be persistent, meeting the Stockholm Convention
criteria for persistence under some circumstances [e.g. (87-91)]. Its regular
use in agriculture and home gardens can cause its accumulation in soil, water,
food, and air (92). After residential applications, chlorpyrifos is detected in flooring,
furniture, toys, dust, and air (93). In a study of urban apartments, chlorpyrifos
lingered on absorbent and soft surfaces for as long as two weeks after application,
including areas not directly sprayed (93). Furthermore, all indoor air and
dust samples collected in a study of homes and day cares in the United States had
chlorpyrifos present, even though the majority had not used pesticides for at least
a week (94). In one study, chlorpyrifos was still measured in the air inside houses
eight years after it had been applied for termite control (95).
There is some evidence that chlorpyrifos can accumulate up the food chain in
certain species, and it has been measured in fish in the Arctic as a result of global
transport (87, 96-98). Residues are commonly found in vegetables, fruit, rice, and
cereal products in many countries. It is also found in fish, dairy products, drinking
water, and even soft drinks in some countries. A survey of chlorpyrifos in pasteurized
milk from Mexico found that 8% of milk sampled exceeded the regulatory
threshold, a sizable proportion when considering how common milk is among
households with children (99).
Biomonitoring/body burden studies (evidence of exposure)
Chlorpyrifos is relatively short lived in people (half is removed from the blood and
fat in about 24 and 60 hours, respectively). Instead of accumulating in the body,
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