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Toxicity Testing for Assessment of Environmental Agents: Interim Report
Pesticide Fact Sheets summarizing many pesticide evaluations conducted since the passage of the FQPA in 1996 are posted on EPA’s web site. Of the 59 chemicals posted, EPA found it unnecessary to apply an FQPA factor—that is, it uses a factor of 1—for all but 11 chemicals. For five pesticides, the agency applied the full FQPA factor of 10 for at least one exposure group and exposure circumstance, such as acute dietary exposure of women of childbearing age. For six pesticides, EPA applied an FQPA factor of 3. In the five cases where the factor of 10 was applied, severe developmental toxicity end points, such as multiple malformations and fetal death, were observed in laboratory animals. In two cases in which an FQPA factor of 1 was applied, a database UF of 10 was used. Both cases were driven by findings from existing studies suggesting effects at lower doses and the need for specific studies to resolve the uncertainty (for example, a developmental-immunotoxicology test).
EPA (2002b) notes that there should be consistency among agency programs, including the pesticide program, in deriving RfDs and RfCs for the same chemical. EPA (2002b) found that broad use of the database UF under the FQPA is characteristic of other agency practices and provided the following guidance on its use in risk assessments:
The [database] “completeness” inquiry should be a broad one that takes into account all data deficiencies. In other words, the risk assessor should consider the need for traditional uncertainty factors not only when there are inadequacies or gaps in currently required studies on pesticides, but also when other important data needed to evaluate potential risks to children are missing or are inadequate.
EPA (2002b) also noted that all agency programs have traditionally considered a group of five studies to be the minimum for deriving a “high-confidence” chronic RfD—two chronic oral studies in different species, two prenatal-development studies in different species, and a multigeneration reproductive-toxicity study in rats. EPA concluded that
the absence of any of these studies suggests that the existing data are not sufficient to address and relieve uncertainties regarding the hazards of the chemical and would typically give rise to the need for a database uncertainty factor to protect the safety of infants and children.