Implicit precaution, scientific inference, and indirect evidence: the basis for the US Environmental Protection Agency's regulation of genetically modified crops

In this study, we explore how the US Environmental Protection Agency (EPA) uses science in its overseeing of genetically modified (GM) plants producing their own pesticides (plant-incorporated protectants or PIPs). Our analysis is based on a systematic review of EPA's product assessments, regulatory decisions and policy documents on GM plants. In regulating PIPs, product characteristics remain the fundamental basis for the agency's risk assessment. However, a recent ruling by the EPA represents a departure from a strict "product" approach to risk assessment. By considering not only product characteristics, but also the process by which a GM crop was developed, the EPA may be seen as adopting a cautionary approach under conditions where current science is unable to resolve whether GM crops and foods impose unique risks by comparison with products derived through conventional breeding. The EPA's case-by-case evaluations of GM products rely heavily on models and indirect measurements interpreted through biological and biochemical principles.