Permethrin assessment

Permethrin Urinary carboxylic Use of existing risk assessment to put biomonitoring results into risk context acid metabolite Appendix B... 

Appendix B provides brief case studies of two pesticides, glyphosate and permethrin, for which a pre-existing risk assessment can help to put biomonitoring results into perspective. In both cases, the Environmental Protection Agency (EPA) has evaluated risks for a wide array of exposure scenarios as part of the reregistration process, and there are biomonitoring data whose interpretation could benefit from these risk assessments. 

Permethrin Urinary carboxylic acid metabolites Exposure pathways risk assessment external dose to toxic effect in animals Biomarker results can be put into risk context by using existing risk assessment... 

Case Examples of Use of Pre-existing Risk Assessments to Interpret Biomonitoring Data Glyphosate and Permethrin... 

Some pyrethroids have as many as eight different isomers, and there are several different types. Acute toxicity of a mixture of two isomers depends on the ratio of the amounts of isomers in the formulation. For example, the female rat s acute oral LD50 of permethrin increases from 224 mg/kg to 6,000 mg/kg as the proportion of transisomer increases from 20% to 80%. The route of exposure also is critical in assessing the acute toxicity of a synthetic pyrethroid. Like DDT and many other registered insecticides, naturally occurring pyrethrins and the synthetic pyrethroids are nerve poisons. 

Roy M, Kraus P, Seegers C et al. (2006). Pyridostigmine, DEET, permethrin and stress a doubleblind, randomized, placebo-controlled trial to assess harm. Submitted for publication. 

Some veterans were exposed to these pesticides by intentional application, but because many exposures were accidental, it has been difficult to assess pesticide exposure accurately and therefore a topical dose in exposed veterans. Permethrin was intentionally impregnated into the soldier s uniform fabric at a concentration of 0.125 mg/cm to help control insect infestation while in the dessert. This pyrethroid insecticide consists of four different isomers (Figure 9.1), with the cis isomer more toxic than the trans isomer. Permethrin is a large moleeule (MW = 391.3) and has a log octanol-water partition coefficient of 6.5, which suggests that it could readily partition from the uniform into the lipophilic stratum comeum layer of the soldier s skin. With a transfer rate of 0.49% per day of permethrin from the fabric to skin, the daily dose was estimated to be 6.8 x 10" mg/kg/day (National Research Council... 

Compared to permethrin, the molecular weight and lipophilicty of DEEP suggest that it should be more readily absorbed across skin. This repellent is more readily absorbed across rodent skin than either porcine or human skin. About 6% of a topical dose of commercially formulated DEET (15% in ethanol) was absorbed across human skin within 8 h (Selim et al., 1995). Our laboratory also reported about 3% dose absorption in poreine skin within this same time period however, absorption in mice skin ranged from 10 to 21% of the dose (Baynes et al., 1997). These data highlight the potential problem of overestimating the risk of DEET in humans if rodent data are used in dermal risk assessment. 

With the above discussion in mind, it may be assumed that chiral xenobi-otics are likely to be present in various foodstuffs, as human food comprises the meat of fish, birds and terrestrial animals, and of course vegetables. Many chiral pesticides are used to control insects in vegetables and cereals, and hence the presence of these pesticides in the food products is to be expected. Only a few reports are available dealing the presence of chiral pesticides in various foodstuffs. The cholinesterase inhibition activity of chiral organophosphorous pesticides, as well as that of toxic organophosphorous pesticides nerve gases, are enantioselective in nature. Scientists at the Microbiological and Chemical Exposure Assessment Research Division of NERL in Cincinnati, USA, have found the chiral insecticide permethrin, a pyrethroid insecticide, in spinach. Similarly, malathion has been observed in blackberry extract [146]. 

A preliminary physiological model for allethrin is presented in Fig. IF, Appendix F. Preliminary ACSL-based physiological models were also written for deltamethrin, cisitrans permethrin, and cisitrans resmethrin (Knaak, unpublished). A PBPK model was developed for deltamethrin (Mirfazaelian et al. 2006 Godin et al. 2010 Tornero-Velez et al. 2010) to assess internal dose levels in various organs and tissues of rats and humans. Deltamethrin was selected to represent the disposition of the pyrethroids, because it is structurally similar to other commercial... 

Rat serum was found capable of hydrolyzing the six pyrethroids studied by Crow et al. (2007), with bioresmethrin and trans-permethrin being hydrolyzed the fastest and cA-permethrin, deltamethrin and esfenvalerate the slowest. Humans lack detectable amounts of CEs in blood. On this basis, the rat should be considered a poor surrogate animal for human health risk assessment at the environmentally low levels at which the pyrethroids normally exist (Crow et al. 2007). 

McGregor DB (1999) Permethrin Joint Meeting, FAO Panel of Experts on Pesticide Residues in Food and the Environment, and WHO Core Assessment Group, Rome. 

K. E. Appel, U. Gundert-Remy, H. Eischer, M. Faulde, K. G. Mross, S. Letzel, and B. Rossbach. Risk assessment of Bundeswehr (German Eederal Armed Forces) permethrin-impregnated battle dress uniforms (BDU), International Journal of Hygiene and Environmental Health, 211, 1-2, 88-104, 2008. 

M. F. Vaughn, and S. R. Meshnick. Pilot study assessing the effectiveness of long-lasting permethrin-impregnated clothing for the prevention of tick bites. Vector Borne Zoonotic Diseases, 11, 869-875, 2011. 

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