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

C. RISK CHARACTERIZATION
The potential health hazard associated with the use of DDVP was considered for occupational and
residential exposures. Non-oncogenic effects were characterized in terms of margins of safety
(MOS), defined as the ratio of the NOEL to the potential exposure dosage. The risk of cancer was
characterized in terms of theoretical probability of excess cancer risk in a lifetime, and is calculated by
potency factor and exposure levels. The critical NOELs (in terms of adjusted dosages) and potency
factors used to address the various exposure scenarios for humans are listed in Table 22.
Table 22.
The critical no-observed-effects levels (NOELs) and potency factors for risk
characterization.
Scenarios
Potential
routes of
human
exposure
Adjusted
NOEL a
ug/kg-day
Corrected
NOEL b
ug/kg-day
Effects in
animal
studies
References c
Acute
occupational
residential
combined
inhalation 650 325 death
(2-3 days)
Thorpe et al.,
1971b
dietary oral 500 500 cholinergic
signs
(within 1 day)
Lamb, 1992
and Lamb,
1993a
Chronic
occupational
residential
combined
inhalation 50 25 brain ChE
inhibition,
reduced
body weights
Blair et al.,
1974
dietary oral 50 50 brain ChE
inhibition and
cholinergic
signs
Markiewicz,
1990*
Potency
factors
rat
mg/kg-day -1
human
mg/kg-day -1
Lifetime
oral
inhalation
q 1 =0.058
q 1 *=0.10
q 1 =0.20
q 1 *=0.35
mononuclear
leukemia
Chan, 1989*
a/
b/
c/
NOELs were adjusted by converting doses to mg/kg-day units using equations in Appendix D.
The NOEL from inhalation studies were corrected for 50% absorption factor. The oral
absorption is assumed to be 100%.
* indicates study was acceptable to DPR according to FIFRA guidelines.
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