Protocols for toxicity- and allergenicity-testing, whether of gene products or plants, should be reconciled across agencies (see section 4.3). Variations among EPA, FDA, and USDA toxicity-testing protocols, other than those dictated by legislative authority, should be minimized or abolished. It should also be noted that the use of “familiarity ” as a guideline to minimize testing can sometimes be inappropriate and warrants caution. Familiarity can be defined as indirect knowledge or experience obtained from similar gene products, plant varieties, or progenitor varieties grown under similar conditions and used for the same purposes in the same way.
In addition to human health concerns, there is concern that gene products of some transgenic and conventional plants may be toxic to nontarget species in the ecosystem. This section reviews and discusses relevant data on such potential nontarget effects of transgenic and conventional pest-protected plants.
It is useful to divide the effects of conventional and transgenic pest-protected plants on nontarget species into direct and indirect effects. Direct effects include the adverse effects of the toxic plant components on nontarget herbivores, omnivores, and microorganisms that feed on live plants (Hare 1992) and on detritivores that feed on dead plants (Horner et al. 1988). When toxic substances are on the surface of a plant, there could also be direct effects on organisms that do not feed on the plant solely caused by contact toxicity or repellence (Farrar and Kennedy 1993).
Indirect effects include adverse effects of genetically modified pest-protected (GMPP) plants through an intermediary species (Bergman and Tingey 1979; Hare 1992; Price et al. 1980). For example, if an herbivore is tolerant of toxic substances in a plant, these substances could be found in the herbivore's digestive system (Price et al. 1980) or even be sequestered in the herbivore's tissues (Brower et al. 1984; Duffey 1980; Tallamy et al. 1998). Such a herbivore can be unpalatable or toxic to some of its predators or parasites because of this biological magnification of plant-defense compounds (Brower et al. 1984; Ferguson and Metcalf 1985; Hoy et al. 1998). If a pest-protected plant causes dramatic decreases in some herbivore or omnivore populations, there will be less nutrient material for the next level in the food chain. It is theoretically possible that a specialized predator, parasite, or pathogen of an affected herbivore could become locally extinct (Riggin-Bucci and Gould 1997).