Humans appear no more sensitive than laboratory animals to the inhibition of red blood cell cholinesterase by dichlorvos.

Inhibition of red blood cell (RBC) cholinesterase is a consistent and sensitive indicator of exposure to dichlorvos (DDVP). Absent human data, default 10-fold adjustment factors for potential interspecies and intraspecies sensitivity differences would be used in developing a reference dose from the no observed effect levels for this endpoint obtained in toxicological assessments of laboratory animals. However, many studies of the cholinesterase-inhibiting effects associated with DDVP exposure have been conducted in humans, including healthy male volunteers, other healthy subpopulations, and diverse clinical subpopulations.