Organophosphates chronic

Following exposure of humans to organophosphates, but not specifically methyl parathion, restoration of plasma cholinesterase occurs more rapidly than does restoration of erythrocyte cholinesterase (Grob et al. 1950 Midtling et al. 1985). These findings are supported by studies of methyl parathion in animals. Erythrocyte cholinesterase levels are representative of acetylcholinesterase levels in the nervous system, and, therefore, may be a more accurate biomarker of the neurological effects of chronic low level exposure of humans to methyl parathion (Midtling et al. 1985 NIOSH 1976). 

People who should not work with organophosphate insecticides are those with organic central nervous system disease, mental disorders, epilepsy, pronounced endocrine disorders, respiratory conditions, cardiovascular diseases, circulatory disorders, gastroenteric diseases, liver or kidney disease, and chronic conjunctivitis and keratitis (Medved and Kagan 1983). 

Dille JR, Smith WS. 1964. Central nervous system effects of chronic exposure to organophosphate insecticides. Aerospace Medicine May 475-478. 

Namba T, Nolte CT, Jackrel J, et al. 1971. Poisoning due to organophosphate insecticides—Acute and chronic manifestations. Am J Med 50 475-492. 

No information was located regarding neurological effects in animals after chronic inhalation exposure to organophosphate ester hydraulic fluids. 

Organophosphate Ester Hydraulic Fluids. No chronic exposure human studies were located. 

Chronic animal studies of organophosphates are few in number, but those that do exist provide a useful base from which to draw toxicological insight. In rats and mice exposed orally to tricresyl phosphate for 2 years, endocrine effects were found in a dose-response pattern and hepatic effects were found. Ovarian interstitial hyperplasia was also observed but was not dose related. No chronic-duration MRLs could be derived because of the limited number of studies. Tricresyl phosphate, a component of certain hydraulic fluids, produced no evidence of carcinogenic activity in assays with rats and mice (NTP 1994). However, another component, tributyl phosphate, was associated with an increased incidence of bladder tumors in rats and mice (FMC 1994a, 1994b). 

Polyalphaolefin Hydraulic Fluids. Because no chronic-duration human or animal inhalation, oral, or dermal exposure studies using polyalphaolefin hydraulic fluids were located, chronic-duration inhalation or oral MRLs could not be derived. Systemic toxicity studies in which animals were exposed via inhalation, oral, and dermal routes would be useful in identifying the end points of toxicity for humans living at or near hazardous waste sites and exposed for chronic durations. Further carcinogenicity studies on individual organophosphate ester components of hydraulic fluids maybe useful. 

Chronic exposure to GD causes forgetfulness, thinking difficulty, vision disturbances, muscular aches/pains. Although certain organophosphate pesticides have been shown to be teratogenic in animals, these effects have not been documented in carefully controlled toxicological evaluations for GD. 

Hikita H, Miyata M, Ishikawa S. 1973. [Experimental study of chronic organophosphate (OP) insecticides in the beagle dog2activities of cholinesterases and residue of OP.] Nichi Gan Kaishi 77 1254- 1265. (Japanese)... 

The general chemical structure of N-methyl carbamate is shown in Fig. 4.4. Common N-methyl carbamates in use today include aldicarb, carbofuran, methiocarb, oxamyl, and carbaryl. N-methyl carbamates share with organophosphates the capacity to inhibit cholinesterase enzymes and, therefore, share similar symptomology during acute and chronic exposure. 

Malathion is an organophosphate cholinesterase inhibitor. Up to 8% of the topically applied dose may be absorbed. Malathion is used as a treatment for head lice, body lice and scabies. It effectively kills both the eggs and the adult lice. Malathion is an insecticide of relatively low human toxicity. However if malathion is used in an indoor environment, as it breaks down into malaoxon, it can be seriously and chronically poisonous. The safety of malathion in pregnancy and in lactating women and in children has not been established. 

Rayner MD, Popper JS, Carvalho EE, et al. 1972. Hyporeflexia in workers chronically exposed to organophosphate insecticides. Res Commun Chemical Pathol Pharmacol 4(3) 595-606. 

Farm workers are especially susceptible to organophosphate insecticide poisoning. Unsafe spraying conditions can lead to accumulated toxicity and chronic symptoms. Since there are many enzymes in the body which are in the serine esterase family along with Achase and can complex... 

Chronic exposure to certain organophosphate compounds, including some organophosphate cholinesterase inhibitors, causes neuropathy associated with demyelination of axons. 

Buchanan, D. et al., Estimation of cumulative exposure to organophosphate sheep dips in a study of chronic neurological health effects among United Kingdom sheep dippers, Occup. Environ. Med., 58, 694-701, 2001. 

Pesticides include a broad range of substances most commonly used to control insects, weeds, and fungi. Insecticides are often subclassified by chemical type as organophosphates, organochlorines, carbamates, and pyrethroids [110]. Some studies have indicated that pesticide exposure is associated with chronic health problems or health symptoms such as respiratory problems, memory disorders, dermatologic conditions, cancer, depression, neurologic deficits, miscarriages, and birth defects [111]. 

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