Application for the Reassessment of a Hazardous Substance under ...

“No information was located on immunotoxicity in humans afterdichlorvos exposure. Only a few studies were located that addressedimmunotoxicity in animals after dichlorvos exposure.Immunosuppression after oral exposure to dichlorvos in rabbits hasbeen reported in three studies (Casale et al. 1983; Desi et al. 1978,1980). A dose-related suppression of the humoral immune responseinduced by S. typhimurium was observed in rabbits (Desi et al. 1978).A single oral dose of 120 mg/kg [b.w.] dichlorvos in male C57B l/6 micethat had been inoculated with sheep erythrocytes 2 days earliersuppressed the primary IgM response observed 48 hours later (Casaleet al. 1983). Severe signs of dichlorvos neurotoxicity were noted, andthe authors stated that the immunosuppression observed in this studymay have been mediated indirectly by toxic chemical stress. It isunknown if the immune suppression noted after dichlorvos exposure inthese studies is secondary to cholinergic stimulation. Immunotoxicitystudies employing atropine prophylaxis to counteract theanticholinesterase effect of dichlorvos are necessary to resolve thisquestion. Additional studies examining potential longer-term effects ofdichlorvos on the immune system by all three routes as well as shorttermeffects by the inhalation and dermal routes would be importantfor estimating human susceptibility for populations exposed for varyinglengths of time at hazardous waste sites.” (Originals not sighted;ATSDR, 1997)WHO (1988) also reviewed Desi et al. 1978, 1980.Dichlorvos reassessment – application Page 249 of 436