Why are some new standards for Specific Pollutants proposed by UKTAG more precautionary?

Where the standards proposed are more stringent, this may be because, there is new toxicological data available that provides evidence that a tighter standard is necessary to protect sensitive species. However the European method also allows for the application for safety factors when setting a standard to address circumstances where our current level of scientific understanding may be lacking. This approach is designed to safeguard the environment and still enable a standard to be set. UKTAG has recommended that where there is not sufficient evidence to justify a high safety factor and where there is unlikely to be improvement in scientific knowledge, we use an existing standard under DSD as an interim value. We have undertaken a review of substances where such concerns exist and identified a number of toxicological studies that would improve our understanding and facilitate the calculation of a more precise safety factor. Subject to the availability of sufficient funding we will endeavour to undertake this work as soon as possible and will bring forward proposals for further standards in due course.