Determining "safe" levels of exposure: safety factors or mathematical models?

The object of regulatory toxicology is to determine "safe" levels of human exposure to toxicants present in the environment. The traditional safety factor approach is compared to more recent mathematical modeling techniques, outlining the underlying assumptions and statistical properties of each procedure. Several linear extrapolation procedures are examined in detail using computer simulation, along with the impact of nonlinear kinetics on the extrapolation process.