This article describes the ongoing debate as to the ability of the US Environmental Protection Agency's (USEPA's) sewage sludge regulations to protect public health and the environment. These regulations, known as the EPA Part 503 Biosolids Rule, or “biosolids rule” for short, are based on risk assessments that some consider inadequate in that they do not address all potential risks. This article provides information about why environmentalists, farmers, and scientists are encouraging the USEPA to adopt a more protective program. It has been suggested that the Precautionary Principle, an emerging general principle of international environmental law, should be used in determining the safety of such a widely used practice as applying waste to the land.