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

VI. TOLERANCE ASSESSMENT
A. BACKGROUND
A tolerance is the maximum amount of pesticide residue that may remain in or on a food, or animal
feed (USEPA, 1991d). The USEPA tolerance program was developed as an enforcement mechanism
to identify illegal residue concentrations resulting from potential non-compliance with the product label
requirements (e.g. improper application rates or methods, inadequate pre-harvest intervals, direct or
indirect application to unapproved commodities). Tolerances are enforced by the FDA, the USDA, and
state enforcement agencies (e.g. Pesticide Enforcement Branch of DPR).
The data requirements established by USEPA for tolerances include: (1) residue chemistry which
includes measured residue levels from field studies, (2) environmental fate studies, (3) toxicology
studies which evaluate the hazards to humans, domestic animals, and non-target organisms, (4)
product performance such as efficacy, and (5) product chemistry which includes physical-chemical
characteristics and analytical method (Code of Federal Regulations, 1992). The field studies must
reflect the proposed use with respect to the rate and mode of application, number and timing of
applications, and formulations proposed (USEPA, 1982).
Currently, the tolerances set by USEPA are at levels necessary for the maximum application rate and
frequency, and not expected to produce deleterious health effects in humans from chronic dietary
exposure (USEPA, 1991d). USEPA uses Reference Doses for non-cancer risks, and negligible levels
(generally defined as a lifetime probability of tumor occurrence at one in a million) for cancer risks as
guides to determine the appropriate levels for dietary exposure.
Assembly Bill 2161 (Bronzan and Jones, 1989) requires the DPR to "conduct an assessment of
dietary risks associated with the consumption of produce and processed food treated with pesticides".
In the situation where "any pesticide use represents a dietary risk that is deleterious to the health of
humans, the DPR shall prohibit or take action to modify that use or modify the tolerance.....". As part
of the tolerance assessment, a theoretical dietary exposure for a specific commodity and specific
population subgroups can be calculated from the product of the tolerance and the daily consumption
rate.
B. ACUTE EXPOSURE
An acute exposure assessment using the residue level equal to the tolerance is conducted for each
individual label-approved commodity. The TAS Exposure-4 software program and the USDA
National Food Consumption Survey (USDA, 1987-1988) are used in this assessment. The acute
tolerance assessment does not routinely address multiple commodities at the tolerance levels since
the probability of consuming multiple commodities at tolerance levels decreases as the number of
commodities included in the assessment increases. A list of all the tolerances is in Appendix A. The
printouts from the TAS program analysis are on file at the Medical Toxicology Branch and are
available on request.
In this document, the tolerances of raw agricultural commodities, milk, eggs, and meats were
evaluated. The tolerance for mushrooms was not evaluated since the use has been deleted from the
labels. Based on the 95th percentile user-day exposures and the acute NOEL of 0.5 mg/kg-day for
cholinergic signs observed in the rats (Lamb 1992; and Lamb 1993a), the MOSs were greater than
800 for all population subgroups for the tolerances of tomatoes, radishes, poultry, eggs, beef, veal,
pork, and sheep. The MOSs were greater than 200 for all population subgroups, with one exception,
for the tolerances of cucumber, lettuce, and milk. The MOS for children (1-6 years) was 160 for the
tolerance of lettuce. The MOSs for all other tolerances were greater than the benchmark level of 100
considered sufficient for the protection of human health.
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