Chlorpyrifos effects

Table 14.7 (continued) Chlorpyrifos Effects on Selected Ecosystems... 

McEwen, L.C., L.R. DeWeese, and P. Schladweiler. 1986. Bird predation on cutworms (Lepidoptera Noctuidae) in wheat fields and chlorpyrifos effects on brain cholinesterase activity. Environ. Entomol. 15 147-151. 

Aldridge, J, E., SeiJler, F. J., Meyer, A., Thillai. I., and Slotkin, T, A. (2003). Serotonergic systems targeted by developmental exposure to chlorpyrifos Effects during different critical periods. Environ. Health Perxpect. Ill, 1736-1743. 

No.strandt, A, C., Padilla, S and Moser, V, C, (1997), The relation-.ship of oral chlorpyrifos effects on behavior, cholinesterase inhibition, and muscarinic receptor density in rat. Pharmacol. Biochem. Behav. 58, 15-23. 

Liu J, Olivier K, Pope CN. 1999. Comparitive neurochemical effects of repeated methyl parathion or chlorpyrifos exposures in neonatal and adult rats. Toxicol Appl Pharmacol 158 186-196. 

Rates of hydrolysis may be influenced by the presence of dissolved organic carbon, or organic components of soil and sediment. The magnitude of the effect is determined by the structure of the compound and by the kinetics of its association with these components. For example, whereas the neutral hydrolysis of chlorpyrifos was unaffected by sorption to sediments, the rate of alkaline hydrolysis was considerably slower (Macalady and Wolf 1985) humic acid also reduced the rate of alkaline hydrolysis of 1-octyl 2,4-dichlo-rophenoxyacetate (Perdue and Wolfe 1982). Conversely, sediment sorption had no effect on the neutral hydrolysis of 4-chlorostilbene oxide, although the rate below pH 5 where acid hydrolysis dominates was reduced (Metwally and Wolfe 1990). 

Assessments of risks associated with the use of chlorpyrifos insecticide products for workers have been made. The assessments are based on the results of field studies conducted in citrus groves, a Christmas tree farm, cauliflower and tomato fields, and greenhouses that utilized both passive dosimetry and biomonitoring techniques to determine exposure. The biomonitoring results likely provide the best estimate of absorbed dose of chlorpyrifos, and these have been compared to the acute and chronic no observed effect levels (NOELs) for chlorpyrifos. Standard margin-of-exposure (MOE) calculations using the geometric mean of the data are performed however, probability (Student s f-test) and distributional (Monte Carlo simulation) analyses are deemed to provide more realistic evaluations of exposure and risk to the exposed population. 

The purpose of this chapter is not to discuss the merits, or lack thereof, of using plasma cholinesterase inhibition as an adverse effect in quantitative risk assessments for chlorpyrifos or other organophosphate pesticides. A number of regulatory agencies consider the inhibition of plasma cholinesterase to be an indicator of exposure, not of toxicity. The U.S. Environmental Protection Agency, at this point, continues to use this effect as the basis for calculating the reference doses for chlorpyrifos, and it is thus used here for assessing risks. 

Rawlings, N.C., S.J. Cook, and D. Waldbillig. 1998. Effects of the pesticides carbofuran, chlorpyrifos, dimethoate, lindane, triallate, trifluralin, 2,4-D, and pentachlorophenol on the metabolic endocrine and reproductive endocrine system in ewes. Jour. Toxicol. Environ. Health 54A 21-36. 

Chlorpyrifos inhibits substrate-borne reception and emission of sex pheromone in Tri-chogramma brassicae, an entomophagus insect massively used as a biological control agent of com borers, among survivors of an LC20 dose. Inhibition was probably due to nervous system effects and was not specific to pheromone communication (Delpuech et al. 1998). 

There have been many accidental spills of chlorpyrifos, but little quantitative assessment of its environmental effects. One exception is a spill in April 1985 in England (Boreham and Birch 1987). In that instance, a truck overturned, spilling 205 L chlorpyrifos into an adjacent stream that drained into the Roding River. A resulting sharp decrease in the number and type of macroinvertebrate benthic organisms in affected parts of the river, compared to unaffected areas, lasted 6 months. In addition, certain chlorpyrifos-resistant benthic organisms were unusually abundant. 

Information is lacking on the effectiveness of chlorpyrifos in large-scale (>40 ha) coldwater ecosystems, typical of those found in Alaska or northern-tier states. Accordingly, initiation of longterm studies in these potential problem areas are recommended. As judged by the available literature, three courses of action now seem warranted. 

Curtail agricultural use of chlorpyrifos in watershed areas pending acquisition of additional data on its transport, fate, and effects, including data on chlorpyrifos flux rates from soils and sediments and its resultant bioavailability. 

Brazner, J.C. and E.R. Kline. 1990. Effects of chlorpyrifos on the diet and growth of larval fathead minnows, Pimephales promelas, in littoral enclosures. Canad. Jour. Fish. Aquat. Sci. 47 1157-1165. 

Clements, R.O. and J.S. Bale. 1988. The short-term effects on birds and mammals of the use of chlorpyrifos to control leatherjackets in grassland. Ann. Appl. Biol. 112 41-47. 

Cripe, G.M., D J. Hansen, S.F. Macauley, and J. Forester. 1986. Effects of diet quantity on sheepshead minnows (Cyprinodon variegatus) during early fife-stage exposures to chlorpyrifos. Pages 450-46 in T.M. Poston and R. Purdy (eds.). Aquatic toxicology and environmental fate ninth symposium. ASTM Spec. Tech. Publ. 921, American Society for Testing and Materials, Philadelphia, PA. 

Hoy, J.B. and PJ. Shea. 1981. Effects of lindane, chlorpyrifos, and carbaryl on a California pine forest soil arthropod community. Environ. Entomol. 10 732-740. 

Mullie, W.C. and J.O. Keith. 1993. The effects of aerially applied fenitrothion and chlorpyrifos on birds in the savannah of northern Senegal. Jour. Appl. Ecol. 30 536-550. 

Nelson, J.H. and E.S. Evans, Jr. 1973. Field evaluations of the larvicidal effectiveness. Effects on Non-target Species and Environmental Residues of a Slow-Release Polymer Formulation of Chlorpyrifos. U.S. Army Environ. Hygiene Agen. Rep. No. 44-022-73/75. Aberdeen Proving Ground, Maryland. 15 pp. 

Rawn, G.P., G.R.B. Webster, and G.M. Findlay. 1978. Effect of pool bottom substrate on residues and bioactivity of chlorpyrifos, against larvae of Culex tarsalis (Diptera Culicidae). Canad. Entomol. 110 1269-1276. 

Solar-Rodriguez, F., M-P. Miguez-Santiyan, A. Reja-Sanchez, V. Roncero-Cordero, and J.-P. Garcia-Cambero. 1998. Recovery of brain acetylcholinesterase and plasma cholinesterase activities in quail (Cotumix cotumix) after chlorpyrifos administration and effect of prahdoxime treatment. Environ. Toxicol. Chem. 17 1835-1839. 

Srivastava, S.K., P.R. Tiwari, and A.L. Srivastav. 1990. Effects of chlorpyrifos on the kidney of freshwater catfish, Heteropneustes fossilis. Bull. Environ. Contam. Toxicol. 45 748-751. 

Tagatz, M.E., N.R. Gregory, and G.R. Plaia. 1982. Effects of chlorpyrifos on held- and laboratory-developed estuarine benthic communities. Jour. Toxicol. Environ. Health 10 41 I -421. 

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