Academic journal article Environmental Health Perspectives

Dermal in Vitro Penetration of Methiocarb, Paclobutrazol, and Pirimicarb: Effect of Nonylphenolethoxylate and Protective Gloves

Academic journal article Environmental Health Perspectives

Dermal in Vitro Penetration of Methiocarb, Paclobutrazol, and Pirimicarb: Effect of Nonylphenolethoxylate and Protective Gloves

Article excerpt

Dermal exposure has become the major route of human occupational exposure to pesticides. Detergents are used as part of formulated pesticide products and are known to change the barrier properties of human skin in vitro. However, studies on the influence of detergents as well as protective glove materials on dermal penetration of pesticides are scarce. In an experiment using in vitro static diffusion cells mounted with human skin, we evaluated the effect of nonylphenolethoxylate on dermal penetration of three extensively used pesticides--methiocarb, paclobutrazol, and pirimicarb--and the protection against dermal penetration offered by protective gloves made of latex or nitrile. There was a general tendency, though not statistically significant for all pesticides, for nonylphenolethoxylate to decrease the percutaneous penetration of the three pesticides. The nitrile generally offered better protection against percutaneous penetration of pesticides than did latex, but the degree of protection decreased over time and depended on the pesticides used. Key wordy, detergents, pesticides, protective gloves, skin absorption. Environ Health Perspect 109:129-132 (2001). [Online 11 January 2001 http://ehpnet1.niehs.nih.gov/docs/2001/109p129-132nielsen/abstract.html

Pesticides are used extensively in horticulture. When they are used repeatedly over long periods of time and personal protective equipment is not used to prevent skin contact, dermal exposure constitutes the major route of human occupational exposure to pesticides. Estimates of dermal exposure and percutaneous penetration of pesticides have therefore become a critical part of risk assessment.

Studies of percutaneous penetration of pesticides have been published from only a few studies of human volunteers. Most such evaluations are based on in vivo animal models or in vitro skin penetration models. Despite a European Community directive (91/414) prescribing the testing of active ingredients as well as commercial formulations, most studies have reported on percutaneous penetration of the active ingredient only, thus failing to acknowledge that solvents as well as detergents are part of the formulated product and may change penetration characteristics (1). Nonylphenolethoxylate (NPE) and similar polyethoxylates have been widely used as detergents in pesticide formulations (2). NPE is not known to cause irritation or allergy in humans, but is known to change the barrier properties of human skin in vitro (2,3). Thus, NPE recently has been demonstrated to facilitate and enhance the dermal in vitro penetration of tritiated water by 60% (4). However, published information on the influence of detergents on dermal penetration of active ingredients is scarce, although some recent studies have addressed permeation of commercial formulations of pesticides while mainly focusing on aspects relating to effects of different solvents (5-7).

Gloves are often prescribed for the mixing, loading, and spraying of pesticides, and field data demonstrate the need to use safety procedures when handling pesticides or plant cultivars recently treated with pesticides (8). The protective abilities of glove materials against pesticides are often evaluated in experimental models using the glove material as the only barrier membrane, and penetration rates and breakthrough times of active ingredients as well as commercial formulations are reported (6,7,9,10). In general, natural rubber shows the least resistance to permeation, whereas nitrile and similar materials demonstrate the highest resistance (11-13). Data from more complete in vitro systems involving glove material situated on top of a skin membrane for prolonged exposure periods are seldom available. However, it may be important to measure dermal penetration with glove material present because large reservoirs of pesticide may reside in the glove membrane for more than 24 hr eliciting potential dermal exposure long after the primary exposure has ceased (14). …

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