Percutaneous absorption of diazinon in humans

Diazinon is an organophosphorus insecticide which, through general use, comes into contact with human skin. To investigate its percutaneous absorption, human volunteers were exposed for 24 hr to 14C-labelled diazinon applied in acetone solution (2 micrograms/cm2) to the forearm or abdomen, or in lanolin wool grease (1.47 micrograms/cm2) to the abdomen. Complete void urine samples were collected daily for 7 days. Percutaneous absorption ranged from 2.87 +/- 1.16% (mean +/- SD, n = 6) to 3.85 +/- 2.16% of the applied dose, and there were no statistically significant differences with regard to site or vehicle of application. In rhesus monkeys, over the 7 days after iv dosing (2.1 microCi [14C]diazinon, 31.8 micrograms) a total of 55.8 +/- 6.8% (n = 4) of the dose was excreted in the urine, and 22.6 +/- 5.2% was eliminated in the faeces (78.4% total accountability). In in vitro percutaneous absorption studies with human abdominal skin, 14.1 +/- 9.2% of the applied dose accumulated in the receptor fluid over 24 hr of exposure to 0.25 microgram/cm2 (acetone vehicle). The calculated mass absorbed was the same (0.035 microgram/cm2) for both in vitro and in vivo absorption through human skin.