Toxicological Aspects of 2,2-Dichlorovinyl Dimethyl Phosphate (DDVP) in Cows, Horses, and White Rats1

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Abstract
Five horses exposed continuously to the vapors of 0.5 mg. DDVP/ft.3 in a closed barn for 22 days displayed mild cholinesterase (ChE) depression in erythrocytes after 7 days followed by recovery to normal ChE concentrations at 11 to 22 days. The plasma was within normal limits of ChE activity throughout the test period. The concentration of DDVP (2,2-dichlorovinyl dimethyl phosphate) in the air varied between 0.24 and 1.48 microgm./liter or 1.4% to 8.4% of the daily DDVP dose. Two cows suckling calves showed normal ChE levels in the crythrocytes while ingesting 200 p.p.m. DDVP daily. Severe depression occurred at 500 p.p.m. DDVP and a single dose of 27 mg./kg. caused cholinergic collapse with recovery. The ChE levels in the calves remained normal throughout the 78-day test. Female rats nursing litters were repeatedly intoxicated by oral administrations of 30 mg. DDVP/kg. The litters of these rats exhibited normal ChE levels in the erythrocytes and plasma as well as normal weight-growth curves. Fresh liver macerates from different animals detoxified DDVP, according to bioassay with Musca domestica L., at a rate of about 500 microgm. DDVP/gm. of liver. These findings clearly demonstrated that DDVP is completely detoxified in the animal body and does not accumulate nor store in animal tissues. The hazard of DDVP is related directly to the weight of acute intake rather than to repeated exposures or metabolic deviation of the compound.