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

No clinical signs were reported; however, Tyl et al. (1992) suggested that the signs could have been
missed because rats were nocturnal animals and the consumption of DDVP in the water was highest
at night. There were dose-related decreases in the plasma, erythrocyte, and brain ChE activities of all
F 0 and F 1 adults, and the levels of inhibition at 20 and 80 ppm were statistically significant (p @ 0.05)
(Table 11). The inhibition of ChE activity was greater in the females than in the males because the
females were exposed to DDVP for a longer time (during gestation and lactation also) and their
dosages were higher. The NOAEL for plasma, erythrocyte, and brain ChE inhibition was 5 ppm (0.5
mg/kg-day for the males and 1.1 mg/kg-day for the females). It should be noted that a LOEL of 5 ppm
may be established for the inhibition of erythrocyte ChE activity of the F 0 females and F 1 both sexes
as well as plasma ChE activity for the F 1 males.
There was no evidence of pathological effects in the reproductive organs. The only significant effect
observed in the pups was the reduction in the body weights of the 80 ppm F 1 pups on postnatal days
14 and 21. After weaning the F 2 a litters, the F 1 females were exposed to DDVP again and mated with
untreated males for the F 2 b litters. There was a reduction (not statistically significant) of fertility at 80
ppm. The number of "abnormal" cycles in the 80 ppm F 1 females was significantly higher (68%) than
in the controls (16%). The NOEL for reproductive toxicity and non-cholinergic endpoints was 20 ppm
(2.7 mg/kg-day estimated from the premating dosage for females) based on the reduction of water
consumption, body weight, fertility, and estrous cycling. This study was considered acceptable to
DPR according to FIFRA guidelines.
Inhalation - Mouse
Crl:CD-1 mice (number of mice used not specified) were exposed to DDVP by inhalation during
breeding (Casebolt et al., 1990). Resin strips (1 by 2.5 inch, 2 by 2.5 inch, and 4 by 2.5 inch) were
placed in the food hopper 4 days prior to mating and continued throughout pregnancy. The air
concentrations measured on day 1 were 1.9 ± 1.2, 3 ± 2.2, and 4.6 ± 2.0 mg/m 3 for the three sizes of
strips, respectively, but were not maintained throughout the experiment. The estimated dosages for
the three air concentrations of day 1 were 3.4, 5.7, and 8.3 mg/kg-day. There were no effects on the
reproductive performances as determined by litter frequency and mean litter size. No clinical signs
were observed. Plasma ChE activity of the treated dams were depressed on days 4 and 7, but not on
day 14. The plasma ChE activity was maximally inhibited on day 4 to 10%, 7%, and 6% of control
values for 1.9, 3, and 4.6 mg/m 3 groups, respectively.
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