Dermal in vitro penetration of methiocarb, paclobutrazol, and pirimicarb.
OBJECTIVE
The dominant route of occupational exposure to pesticides in horticulture is dermal. However, preventive measures are seldom used when handling plant cultures recently treated with pesticides, thus causing significant dermal exposure and potential absorption. Assessment of exposure often depends on biological monitoring of blood or urine samples. The skin often acts as a temporary reservoir for chemicals before absorption. Failure to consider the lag time between dermal exposure and appearance of pesticide or metabolites in the general circulation may lead to false conclusions about assessment of exposure.


METHODS
In an experimental model in which in vitro static diffusion cells were mounted with human skin, dermal penetration of three extensively used pesticides (methiocarb, paclobutrazol, pirimicarb) was evaluated.


RESULTS
Pirimicarb and paclobutrazol had comparable rates of dermal penetration and lag times of around 18 hours. Methiocarb had a considerably shorter lag time. Dermal penetration continued for extended periods after exposure had ended.


CONCLUSIONS
With lag times sometimes considerably longer than a normal working day, biological monitoring at the end of exposure may seriously underestimate the actual exposure. There may be implications for regulatory guidelines, which often require only 24 hour observation periods.
Nielsen
J B
JB
Institute of Public Health, University of Southern Denmark, Winsløwparken 17, DK-5000 Odense C, Denmark. jbnielsen@health.sdu.uk
Nielsen
F
F
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007306:Insecticides / Q000493:pharmacokinetics*; D008714:Methiocarb / Q000493:pharmacokinetics*; D008875:Middle Aged; D016273:Occupational Exposure / Q000009:adverse effects; D010539:Permeability; D010937:Plant Growth Regulators / Q000493:pharmacokinetics*; D012867:Skin / Q000737:chemistry; D012869:Skin Absorption / Q000502:physiology*; D013997:Time Factors; D014230:Triazoles / Q000493:pharmacokinetics*
D007306:Insecticides; D010937:Plant Growth Regulators; D014230:Triazoles; C053370:paclobutrazol; D008714:Methiocarb