potentially harmful effects of ecologically based controls on human and environmental health. Generally speaking, the risks posed by biological-control organisms and resistant plants are not the same as those associated with broad-spectrum synthetic chemical controls. The specificity of the mode of action of the biological organism, or resistant plant with respect to target pest, the likely constrained geographic area of biologically based control measures, and the method of deployment all contribute to the likelihood of safety. Human and environmental health risks of biological controls are not only different in kind from those of most conventional chemicals but also lower in the degree of hazard potentially posed. In many cases, the risks of continued use of chemical controls may be greater than the risks of instituting ecologically based strategies. By the same token, for pest problems not currently addressed by conventional chemicals, the use of ecologically based controls may indeed present some risks, but to the best of this committee's knowledge there needs to be more data to make a more accurate risk assessment. Nevertheless, the history of biologically based resistance genes supports their continued use and their risks may well be acceptable compared to those attributable to lack of effective control.

Biological-control products include genes or gene products derived from living organisms that kill, disable, or otherwise regulate the behavior of living organisms. In this category of controls, the product of a living organism rather than the living organism itself is used to manage a pest or pathogen population. Assessment of the potential risks of biological-control products, as chemical pesticides, must include their effects on environmental and human health. The nature of these risks is in large part a function of the mode of action of biological molecules, which range widely from toxicity to attraction. There are many natural products, including Bt toxins, pheromones, floral attractants, insect growth regulators, and plant growth regulators that have been registered as biochemical pesticides (U.S. Environmental Protection Agency, 1994a). Many others are being proposed for exemption from regulation by EPA. Fermentation products and plant extracts with a toxic mode of action have promise, but their development may be hindered if they are automatically regulated as conventional synthetic chemicals.

Effective oversight must also account for the likelihood that the particular kinds of human or environmental risks posed will vary with the biological-control organism, product, or resistant plant. And, the risks may vary in degree if not in kind depending on the particular agronomic setting of the pest/crop combination. Consequently, human health considerations may be paramount in some cases, whereas environmental effects (e.g., adverse impacts on nontarget organisms) may be the only cause for concern in other cases. Accommodating such variation in risk profiles across the many types of ecologically based controls will be key to constructing effective but not burdensome oversight.

Significant markets for agrochemicals in many cropping systems justify investment in the regulatory costs involved in their development, and some biologi-

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