Chlorpyrifos sources

Lawns also represent an urban ecological problem on a vast scale. In the United States, the chemicals of lawn maintenance-including dichlorophenoxy-acetic acid (2,4-D), glyphosate, diazinon, and dicamba-are significant contributors to nonpoint source water quality problems that continue to elude solution almost 30 years after the passage of the Clean Water Act. Lavm pesticides are applied on a scale to rival agricultural toxins 23% of the total 2,4-D applied in the United States is used on lawns 22% of glyphosate, 31% of chlorpyrifos, and 38% of dicamba used nationally is applied to home lavms. ... 

The chlorpyrifos example described in Appendix B illustrates another caveat related to biomarkers that are urinary metabolites. A metabolite can sometimes appear in urine not only as a result of parent-chemical uptake and metabolism but also as a result of uptake of the metabolite from environmental media (Tu et al. 2005 Wilson et al. 2003). Thus, the biomarker for chlorpyrifos, 3,5,6-trichloro-2-pyridinol (TCP), occurs in a wide variety of environmental media, and the concentration in foods surpasses that of the parent chemical (Morgan et al. 2005). If the intake of the metabolite from environmental sources is substantial in comparison with that of the parent chemical, as in the case of chlorpyrifos and TCP, the extrapolation of urinary biomarker concentration to parent-chemical exposure dose is uncertain. 

FIGURE 4.2 Mortality of fathead minnows in relation to acetylcholinesterase activity.3 a As measured in the brain tissue following (A) a 14-day exposure to a ternary mixture of azinphos-methyl, diazinon, and chlorpyrifos in a concentration-response study and (B) a 7-day exposure to a ternary mixture of azinphos-methyl, diazinon, and chlorpyrifos applied as equipotent (toxic equivalent [TE]) mixtures. Note Dashed lines correspond to 50% reduction in AChE activity the dashed-dotted line corresponds to 50% mortality. Source Redrawn from Sibley et al. (2000). 

FIGURE 4.4 Species sensitivity distribution (SSD) curves for different aquatic species groups for the insecticide chlorpyrifos. Note Shown are the toxicity data of arthropods, other invertebrates, fish, and algae. Results of the logistic regression on these data are represented by lines. Source Data were obtained from ECOTOX (USEPA 2001). 

Communities in India may also be exposed to hazardous cotton pesticides through the contamination of cottonseed and cottonseed derivatives - an important source of edible oil. Because of the intensive use of hazardous pesticides in cotton production much of the cottonseed oil entering the Indian food chain may be heavily contaminated . One analysis of cottonseeds collected from 5 locations in Punjab found detectable residues of the cotton pesticides ethion (WHO II), cypermethrin (WHO II), endosulfan (WHO II), chlorpyrifos (WHO II) the latter being 2 of the most common pesticides applied to cotton in India ... 

FIGURE 66.46. Dependence of the reactivation activity on the length of the linker. Source of enzyme — rat brain homogenate inhibitor - chlorpyrifos time of inhibition - 30 min time of reactivation - 10 min pH 7.6 25°C oxime concentration 10 M. (Kuca et al, 2003c). 

Recent findings of indoor exposure studies of chlorpyrifos indicate that young children are at high risk to this semivolatile pesticide [134]. Even after a single broadcast use of chlorpyrifos by certified applicators in apartment rooms, it continued to accumulate on children s toys and hard surfaces 2 weeks after spraying. The estimated chlorpyrifos exposure levels from indoor spraying for children were estimated to be approximately 21-119 times above the current recommended reference dose from all sources [123]. 

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