Dr Nilsson examines the economic and environmental dangers of the "precautionary principle" - the idea that a substance should only be used if there is proof that it will cause no harm. Dr. Nilsson argues that legislation should be based on sound science, not blind 'precaution'. He laments the fact that Sweden has been at the forefront of pushing the precautionary approach. Dr Nilsson, an expert in biochemistry and radiation biology, is a senior toxicologist at the National Chemicals Inspectorate in Sweden and professor at the University of Stockholm, Sweden. He was previously employed by the Swedish Environmental Protection Agency, where he worked to reduce lead in gasoline. He has offered his chemical expertise to many developing countries, and his recommendations were incorporated into law in India.