The 1994 EPA document requested comments on a proposal to exempt plant-pesticides that acted primarily by affecting plants and “that act through nontoxic modes of action.” The types of substances that clearly are in this category are structural barriers such as plant hairs; substances that inactivate or resist toxins that are produced by pests; and substances that decrease chemical components needed for pest growth. As discussed in chapter 2 (section 2.4 and section 2.5), these exemptions are unlikely to result in any new human exposure to harmful substances.
However, within the same category the 1994 EPA document also discusses exempting plant hormones. Plant hormones often cause multiple changes in plants, including changes in secondary metabolites that might be toxic, so the scientific basis of such an exemption is questionable.
As with the exemption of VCPs, the categorical exemption of substances that act through nontoxic modes of action mostly considers human health effects. As outlined in previous sections of our report ( section 2.6 and section 2.7) there is a need to consider separately the impact of such substances on nontarget species and the potential for the genes that code for these substances to move to feral populations or weedy relatives of the crop, where they could increase recipient plants' fitness. Categorical exemption under FIFRA might not be scientifically justifiable.
The 1994 EPA document states that
any food safety questions beyond those associated with the plant-pesticide, such as those involving changes to food quality or raised by unexpected or unintended compositional changes, are under FDA's jurisdiction. Similarly, food safety issues associated with alterations in levels of a substance with pesticidal properties, or the appearance of a substance with pesticidal properties, that occur as an unintended consequence of modifications to a non-pesticidal trait would also fall under FDA's authority.
That is an important statement and shifts an important component of pest-protected plant assessment to FDA.
As discussed previously in this report (section 2.4.1 and section 2.5.2), genetic changes that result in production of a specific plant protectant can result in production of biologically active compounds other than the in-