Absorption of pesticides

MAFF/Joint Medical Panel of the Scientific Subcommittee on Pesticides of the Ministry of Agriculture, Fisheries, and Food and the Toxicology Committee of the British Agrochemical Association (1986/1992) Estimation of Exposure and Absorption of Pesticides by Spraying Operators, MAFF, Pesticides Registration Department, Harpenden Laboratory, Harpenden, Herts, England. 

Chester, G. (1993) Evaluation of agricultural worker exposure to, and absorption of, pesticides, Am. Occup. Hygiene, 37 509-523. 

Grissom, R.E., Jr. C. Brownie, and F.E. Guthrie. 1985. Dermal absorption of pesticides in mice. Pestic. Biochem. Physiol. 24 119-123. 

Holmstedt (1959) and Brown and Muir (1971) have reviewed perocular absorption of pesticides. More recently, Sinow and Wei (1973) have shown that the quartemary herbicide paraquat can be lethal to rabbits if applied directly to the surface of the eyes. Parathion, in particular, is exceedingly toxic when administered via the eye, a concern that must be kept in mind for the protection of pesticide applicators. 

R. P. Moody, B. Nadeau, and I. Chu. In vitro dermal absorption of pesticides VI. In vivo and in vitro comparison of the organochlorine insecticide ddt in rat, guinea pig, pig, human and tissue-cultured skin. Toxicol. In vitro 8 1225-1232 (1994). 

The three main barriers upon which pesticide will impinge are the skin, the lungs and the gastrointestinal tract. Each of these barriers possesses a unique structure and function which will influence the absorption of pesticide into the bloodstream. Although some product may exert local contact effects, it is usually only after they have been absorbed that, they exert their toxic effects therefore, it is important to understand the extent of the absorption. 

Ohori, Y., Ihashi, Y. (1987) Foliar absorption of pesticides using an isolated cucumber membrane. Res. Dev. Rev.-Mitsubishi Chem. 1(2), 22-26. 

IMP (1986). UK Predictive Exposure Model (POEM) Estimation of Exposure and Absorption of Pesticides by Spray Operators, UK Scientific Sub-committee on Pesticides and British Agrochemical Association Joint Medical Panel, Pesticides Safety Directorate, York, UK. 

Thus, despite the value of human volunteer studies, the technical and ethical constraints for studying dermal absorption of pesticides in human volunteers prevail. As a consequence, only limited data on the dermal absorption of chemicals are available from human volunteer studies. This is in contrast to pharmaceutical products, where the use of human volunteers is considered to be the only relevant approach to generate data of precise relevance to man. 

In another dermal penetration study, it was shown that the absorption of the insecticide carbaryl was enhanced by the solvent acetone and the surfactant sodium lauryl sulfate. The synergist PO significantly increased the absorption of carbaryl when added to the acetone-carbaryl rnixJ31 This study points out both the enhanced absorption of pesticide by individual inert additives as well as the further enhanced mixture effect. 

Bronaugh, R. L. 1985. In vitro methods for the percutaneous absorption of pesticides. In Dermal exposure to pesticide use, edited by R. Honeycutt, G. Zweig, and N. N. Ragsdale. Washington, D.C. American Chemical Society, pp. 33—41. 

Because silicas can be manufactured to conform to food-grade regulations, they can be used to absorb essential oils, flavors, and feed supplements such as choline chloride. The absorption of pesticides is also a... 

As can be clearly appreciated from the previous presentation, there arc numerous experimental variables that have a major impact on the assessment of dermal absorption of pesticides. This was clearly seen with studies involving different methods (in vitro vs in vivo), different species, different doses, or application conditions such as occlusion. 

A similar conclusion was derived from analysis of how data are used in making pesticide risk assessments, where the authors concluded that the inability to match a specific exposure scenario to available data (c.g., species and duration of dosing) led to overestimation of absorption and thus risk Ross et al., 2000). The take home lesson from this chapter is that the experimental conditions under which pesticide absorption studies are conducted often overshadow differences between individual compounds, as can easily be appreciated in the classic studies comparing absorption of pesticides in mice (Shah el ai, 1981) versus humans (Fcidmann and Maibach, 1974). 

Maibach, H., and Feldmann. R. (1974). Systemic absorption of pesticides through skin of man. Occupational exposure to pesticides Report to the Federal Working Group on Pest Management for the Task Group, pp. 120-127,... 

Zendzian, R. P. (1994). Demial absorption of pesticides. In Pesticide As.se.tsmeitt Guideline.s. Subdivision F, Hazard Evaluation. Humans and Domestic Animals, Series 85-3. Office of Pesticide Programs, U.S. Environmental Protection Agency, Washington, DC,... 

The radiotracer method has also been used in hiunan subjects if the test compoimd is not toxic (Feldmann and Maibach, 1969, 1970, 1974). This approach was employed to assess percutaneous absorption of pesticides in swine (Qiao etal., 1994), in human testing of ultraviolet filters (Benech-Kieffer et al., 2003), and for determination of topical absorption of cosmetics (Malhotra et al., 2001) for clinical safety assessment. 

Navidi, W.C. and Bunge, A.L. (2002). Uncertainty in measurements of dermal absorption of pesticides. Risk Analysis, 22, 1175-1182. 

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