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

treatment. No neuropathologic lesions were observed. The LOEL was 5 mg/kg based on reduction of
spinal cord ChE, and brain and spinal cord neurotoxic esterase activities.
Inhalation - Rat
Male rats (strain not specified, number of rats used unspecified) were exposed to DDVP (purity not
specified; at nominal concentrations of 0.05 to 90 ug/L) for 4 hours (Blair et al., 1975). Mild signs of
intoxication (lethargy and pupillary constriction) were observed in the 90 ug/L group. The NOEL for
cholinergic signs was 50 ug/L (adjusted dosage of 8 mg/kg-day).
Inhalation - Monkey
Two experiments were conducted with rhesus and cynomolgus monkeys exposed to warehouses
treated with DDVP applied as an aerosol (Durham et al., 1959). In the first experiments, monkeys
(2/dose) were exposed to DDVP-treated warehouses (0, 0.5, 1.0, or 2.0 mg/ft 3 ) 24 hours after
treatment. The measured air concentrations showed that DDVP levels declined with time. For 2.0
mg/ft 3 , the peak level was 2.2 mg/ft 3 and declined to 0.14 mg/ft 3 and 0.07 mg/ft 3 after 24 and 72 hours,
respectively. In the second experiment, monkeys (2/dose) were placed in warehouses to be treated
with DDVP at 1.0 or 2.0 mg/ft 3 twice a week for 6 weeks. The monkeys were removed from the
treatment area prior to application and returned 12 hours after application. In the first experiment,
because the baseline levels of plasma and erythrocyte ChE were variable for each monkey and
between monkeys, no treatment related effects were detected. In the second experiment with multiple
applications and longer duration of exposure, a dose-related decrease in the plasma and erythrocyte
ChE activities was observed after 50 days of exposure (data were presented only in graphs). After
removal from exposure, the activities of both plasma and erythrocyte ChE recovered toward baseline
levels.
Inhalation - Human
In several human studies, brief continuous exposures to DDVP aerosol up to 10 mg/ft 3 (3.5 mg/L)
either generated by no-pest strips or solution left for evaporation did not result in statistically
significant inhibition of plasma or erythrocyte ChE activities (Durham et al., 1959; Shell Chemical Co.,
1965).
In a study conducted with DDVP resin strips (1 strip/30 m 3 , Vapona Strips) in a hospital, the effects
of DDVP exposure on 125 patients (men with and without liver disease, women during labor and
postpartum, and sick children) were studied (Cavagna et al., 1969). After 24 hours of exposure,
plasma ChE activity of the women was not affected while the activity for the other groups were
inhibited. The extent of the inhibition, expressed as percent of control values, for DDVP air
concentrations of 0.1-0.28 mg/m 3 were 28-65% for men without liver disease, 35-67% for men with
liver disease, and 55-92% for children. For DDVP air concentrations of 0.02-0.1 mg/m 3 after 16 hours
of exposure, only the plasma ChE activity of the men with liver disease was lowered (35-57% of
control values). Based on the estimated DDVP intake per day from the report and the DPR default
body weights of 55 kg for adults and 10 kg for children, the NOEL for plasma ChE inhibition was 0.014
mg/kg-day for children, 0.02 mg/kg-day for men without liver disease, and 0.026 mg/kg-day for
women. Since men with liver disease were affected by both levels of DDVP, the LOEL was 0.006
mg/kg-day. There was no effect on erythrocyte ChE activity.
In another hospital study, new-born babies (22) were exposed to DDVP (1 strip/30 to 40 m 3 ,
Vapona Strips) released from resin strips with a time-weighted average air concentration of 0.15
ug/L for 18 hours per day for 5 days (Cavagna et al., 1970). No significant depression of plasma and
erythrocyte ChE activities was found. The estimated daily dose was 0.07 mg/kg-day assuming a
respiratory rate of 0.46 m 3 /kg-day.
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