Dichlorvos (DDVP) Risk Characterization Document - California ...

and total ChE activities intermittently during the study in all groups except for the 5 ppm group. After
50 days of treatment, plasma and erythrocyte ChE activities of the 15 ppm group were depressed to
87 and 57%, respectively of control values. After 70 days, the erythrocyte and plasma ChE activities
of the 15 ppm group were 54% and 66% of control values. The NOEL for both plasma and
erythrocyte ChE inhibition was 5 ppm (adjusted 0.3 mg/kg-day). The only clinical signs (time of onset
was not specified) were increased activity and urinary output in the 25 ppm and 50 ppm groups. The
NOEL for clinical signs was 15 ppm (adjusted 1.0 mg/kg-day).
Dietary - Cattle
Two dairy cows were fed increasing amounts of DDVP (100% purity) in the feed daily for 1 to 12 days
(Tracy et al., 1960). A newborn and a heifer were also exposed to DDVP from the cow milk or in the
feed. When the milk cows were fed 200 ppm DDVP daily for 7 days, there was no effect on
erythrocyte ChE activity. Increasing the diet concentration to 500 ppm (4.5 mg/kg) for 12 days
resulted in greater than 75% depression of erythrocyte ChE activity. The oral shock dose (dose which
caused cholinergic signs of salivation, diarrhea, tremors, and convulsions) determined for one of the
cows was 3000 ppm (27 mg/kg). After 20 exposures, no detectable level (less than 0.17 ug/ml) of
DDVP was found in the milk as determined by a bioassay with flies using death as the endpoint.
Plasma and erythrocyte ChE activities in the suckling calves were not significantly affected by the
treatment to the mothers.
Dermal - Cattle
The effect of DDVP on two cows after dermal application to the back, front shoulders, and upper back
portions of the neck was studied using either a 1% DDVP aqueous solution, a 1% DDVP emulsion, or
a 10% suspension (Tracy et al., 1960). The solutions were applied on the skin daily for 10-11 days.
No cholinergic signs were observed, and there was no inhibition of erythrocyte ChE activity.
Inhalation - Human
Human subjects (60 male inmates) were housed in Army barracks for at least 10 hours and exposed
to DDVP aerosols released nightly every 30 minutes per hour for about 3 hours for either 14 days
(phase I) or eight 30 minutes per night, 3 to 4 nights per week for 3 weeks (phase II) to simulate
aircraft environments with DDVP applications (Rasmussen et al., 1963). All the volunteers were given
physical examinations, plasma and erythrocyte ChE measurements, airway resistance, and visual
tests. The DDVP concentrations in the air were 0.14 to 0.33 ug/L during phase I, and 0.15 to 0.55
ug/L during phase II. No treatment-related findings were reported for phase I. The only significant
finding in phase II was the inhibition of plasma ChE activity which returned to the pre-exposure level
upon termination of the experiment (data as mean values were presented in a graph).
The plasma and erythrocyte ChE activities of 13 workers (both sexes), who were exposed to DDVP at
an average air concentration of 0.7 mg/m 3 in the production of DDVP-releasing vaporizer, were
monitored for 8 months (Menz et al., 1974). The average plasma and erythrocyte ChE activities,
measured weekly of the workers during production, were 35% and 60%, respectively, of the levels
measured before production. The ChE activities had returned to the pre-production level one month
after exposure ceased (data were presented in graphs). Medical examinations and blood chemistry
performed during the study were within normal limits.
DDVP, in polyvinyl resin formulation pellets, was administered to male subjects in single doses up to
32 mg/kg and repeated doses up to 16 mg/kg-day for up to 3 weeks (Slomka and Hine, 1981). Of the
107 men who received DDVP in single doses of 0.1 mg/kg to 32 mg/kg, there was a dose-related
inhibition of plasma and erythrocyte ChE activities as compared to pre-treatment values. At the
highest dose (32 mg/kg), the inhibition was 20-30% and 55-75% for plasma and erythrocyte ChE, of
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