Chlorpyrifos
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chemicalWATCH Factsheet CHLORPYRIFOS On June 8, 2000, the U.S. Environmental Pro- In animals, chlorpyrifos transforms to In 1999, EPA’s Office Pesticide Programs, Health tection Agency (EPA) and Dow AgroSciences, chlorpyrifos-oxon, which is about 3000 times as Effects Division, reported that four pesticides, reached an agreement to stop the sale of most potent against the nervous system as chlorpyrifos phosmet, proetamphos, chlorpyrifos, and home, lawn and garden uses for chlorpyrifos itself. dimethoate, had consistently high rankings in because of its health risks to children. being responsible for symptoms, health care fa- Chlorpyrifos is linked to delayed peripheral neu- cility visits, hospitalizations, and fatal outcomes What is Chlorpyrifos? ropathy (degenerative lesions of sensory, motor, in adults and children. These four organophos- or reflex nerves). Italian researchers published a phate pesticides are responsible for 90% of pes- Chlorpyrifos (trade names include DursbanTM and disturbing report of an acute chlorpyrifos poi- ticide exposures reported in children under six to LorsbanTM), one of the most widely used insecti- soning episode, resulting in delayed peripheral the Poison Control Centers around the country cides in the U.S. with 20 to 24 million pounds neuropathy. There are also reports of EEG from the 1993-1996. The report also stated that applied annually, has been linked to thousands of (brainwave) pattern, sleep pattern and behavioral “children, under six exposed to organophosphates, pesticide poisoning incidents. This Dow changes lasting over a year following exposure to were three times more likely to be hospitalized, AgroSciences, previously DowElanco, product organophosphate insecticides. five times more likely to be admitted for critical is a broad-spectrum chlorinated organophosphate care, and four times more likely to have experi- insecticide. Organophosphates are cholinesterase inhibitors. enced a major medical outcome or death, than if Organophosphates bind irreversibly to the ac- exposed to some other, non organophosphate, Chlorpyrifos is registered for the control of cut- tive site of an essential enzyme for normal nerve pesticide.” worms, corn rootworms, cockroaches, grubs, flea impulse transmission, acetylcholine esterase beetles, flies, termites, fire ants, mosquitoes, and (AchE), inactivating the enzyme. A common di- There are also a wide range of adverse environ- lice. It is used as an insecticide on grain, cotton, agnostic for poisoning is to assay for blood AchE mental effects linked to chlorpyrifos, include tox- fruit, nut, and vegetable crops, as well as on lawns depression. It can take many weeks for new en- icity to: beneficial insects, freshwater fish, other and ornamental plants. It is also registered for zyme to be resynthesized. Repeated or prolonged aquatic organisms, bird, a variety of plants, soil direct use on sheep and turkeys, for horse site exposure to organophosphates may result in the organisms, and domestic animals. It has been treatment, dog kennels, domestic dwellings, farm same effects as acute exposure including delayed shown to bioaccumulate in fish and synergisti- buildings, storage bins, and commercial establish- symptoms. cally react with other chemicals. Chlorpyrifos ments. may be toxic to some plants, such as lettuce. A 1996 study of children exposed to chlorpyrifos Residues remain on plant surfaces for approxi- ChlorpyrifosToxicity and Health Effects in utero found that extensive and unusual pat- mately 10 to 14 days. Data indicate that this terns of birth defects, including brain, nervous insecticide and its soil metabolites can accumu- Chlorpyrifos is acutely toxic to bees, birds, mam- system, eyes, ears, palate, teeth, heart, feet, late in certain crops. mals, aquatic life, and certain species of algae, the nipples, and genitalia. Published literature and rat LD50 is 135 mg/kg. EPA documents contain reports that identify Chlopyrifos Residues / Persistence similarities in defects found in test animals and Poisoning from chlorpyrifos may affect the cen- children exposed to chlorpyrifos. There are few data available on air levels or sur- tral nervous system, the cardiovascular system, face residues following application either as a and the respiratory system as well as a skin and In 1997, EPA Office of Pesticide Programs’, termiticide or for indoor pest control. The Ameri- eye irritant. Acute exposure can result in such Health Effects Division reported that can Conference of Governmental Industrial Hy- symptoms as numbness, tingling sensation, in- chlorpyrifos is one of the leading causes of acute gienists recommends an occupation air level guide- coordination, dizziness, vomiting, sweating, nau- insecticide poisoning incidents in the U.S. line of 200 micrograms/cubic meter (µg/m3) for a sea, stomach cramps, headache, vision distur- forty hour work week. The National Academy bances, muscle twitching, drowsiness, anxiety, A U.S. News & World Report investigation, “The of Sciences proposed a 10µg/ m3 air level for the slurred speech, depression, confusion and in ex- stuff in the backyard shed,” (November 8, 1999, general public, while EPA has proposed an air treme cases, respiratory arrest, unconsciousness, page 64-68) reports that since 1992, Dow limit of 0.49µg/m3 for children, and 1µg/ m3 for convulsions, and death. Persons with respiratory AgroSciences and predecessor manufacturers adult exposures. ailments, recent exposure to cholinesterase in- have sent approximately 7,000 reports of hibitors, cholinesterase impairment, or liver mal- chlorpyrifos-induced reactions to EPA. The Work by Fenske et al. found that air levels 24 function are at increased risk from exposure to agency, according to the report, suspects hours after a proper application were as high as chlorpyrifos. Chlorpyrifos has also been linked chlorpyrifos in 17,771 incidents reported to the 30µg/ m3 in the infant breathing zone, 60 times to Multiple Chemical Sensitivity (MCS). U.S. Poison Control Centers between 1993 -96. EPA’s limit. Furthermore, Fenske calculated that Beyond Pesticides 701 E Street, S.E., Suite 200, Washington DC 20003 202-543-5450 (v) • 202-543-4791 (f) [email protected] • www.beyondpesticides.org infant exposure through inhalation and skin ab- bon dioxide and water. The half-life of and direct application pet care products. Con- sorption may be more than five times the human chlorpyrifos in water is relatively short, from a centrated forms of chlorpyrifos no longer be sold threshold for acute effects (No Observable Ef- few days to two weeks. It adsorbs readily to to consumers, and the ready-to-use products now fect Level). The researchers state that, “Expo- sediments and organic matter, its half-life in soil include labels which forbid use in dangerous ar- sures to cholinesterase inhibiting compounds fol- is usually between 60 and 120 days, but can range eas, such as on/around furniture and toys. lowing properly conducted broadcast applica- from 2 weeks to over one year, depending on the tions could result in doses at or above the thresh- soil type, climate, and other conditions. In 1994, an unapproved formulation of old of toxicological response in humans.” chlorpyrifos was sprayed on General Mills, Inc., The granular formulation of chlorpyrifos has been oats used to make 160 million boxes of Cheerios In common with most organophosphates, found to be more persistent and may persist as and Lucky Charms. According to EPA, most of chlorpyrifos has a relatively short biological half- long as 180 days. The major biological metabolite the cereals had been consumed before the adul- life, roughly 24 hours in blood, and 60 hours in and environmental breakdown product is 3,5,6- teration was detected. This is especially disturb- fat (assuming that multiple or continuous expo- trichloro-2-pyridinol (TCP). According to an EPA ing due to the pervasive nature of Cheerios and sure does not occur) and it has shown no poten- memorandum, groundwater monitoring at a Cape its consumption by young children. tial to bioaccumulate in mammals. Its half-life Cod golf course detected TCP in samples. Re- indoors is estimated to be 30 days. Various stud- ports from the USDA Southern Forest Experi- In an unrelated incident, Dow AgroSciences ies of different treatment methods show mental Station note that the termiticide formula- agreed to pay $876,000 for failing to disclose chlorpyrifos present up to eight years post ap- tion is effective against termites for more than 15 adverse effects incidents involving chlorpyrifos plication. A 1998 study found that chlorpyrifos years. under a consent agreement. The agreement cov- accumulated on furniture, toys, pillowcases, and ers 337 violations over ten years of FIFRA other sorbant surfaces up to two weeks after in- Chlorpyrifos History §6(a)(2) reporting requirements. door application. In 1997, EPA and Dow AgroSciences agreed to In June 2000 EPA and Dow AgroSciences agreed Chlorpyrifos is sensitive to light, alkaline sub- restrict several uses of chlorpyrifos, including a to a stop sale of many uses of chlorpyrifos due stances such as bleach, and microbial degrada- ban of the chemical for indoor broadcast flea con- to its health risk. For information on the recent tion. Eventually, it degrades completely to car- trol, indoor total release fogging, paint additives, phase-out agreement, please contact us. Chlorpyrifos chemicalWATCH Factsheet Bibliography Aspelin, A., 1997. Pesticide Industry Sales and Usage: pounds.” Agrichemical: Preparation