The precautionary principle in environmental regulations for drinking water

The precautionary principle has been proposed as a means of providing increased safety for consumers of drinking water. While the principle has received increased attention over the past 2 decades, it remains rather poorly defined both in law and practice. Hence, the implications for application in risk-based decisions on water quality are not fully developed. This paper examines a series of philosophical, practical and decision-theoretic issues related to the application of the principle in such decisions, highlighting areas where at least the intent of the principle is already well embedded in environmental regulation through margins of safety, and identifying residual issues. A conclusion is drawn that full application of the principle may be driven forward both by programmes such as REACH in the EU, and by the emerging Water Framework Directive and multi-stakeholder approaches to climate change mitigation and adaptation.