Cumulative conservatism

Certainly errors should be conservative, but cumulative conservatism reduces accuracy and usefulness while raising costs. 

If data have already been generated for risk assessments, it may be possible to use these without further quality assessment (as is done in the European Union), but any new and relevant information should be considered scientifically. Usually, the lowest acute and long-term toxicity data for a species should be used (if the endpoint is relevant at the population level and is derived from a validated study). If valid data for the same endpoints and the same species exist, the geometric mean should be taken. This value is then used together with other species values to calculate the EQSs. Use of a mean value in this situation minimizes cumulative conservatism that is, always using the most conservative data point, especially when additional valid data are available, will lead to too much conservatism, giving rise to an EQS that may be unrealistically low. 

Another way to evaluate risks is to calculate the sensitivity of the total risk estimates to changes in assumptions, frequencies, or consequences. Risk analysts tend to be conservative in their assumptions and calculations, and the cumulative effect of this conservatism may be a substantial overestimation of risk. For example, always assuming that short-term exposure to chemical concentrations above some threshold limit value will cause serious injury may severely skew the calculated risks of health effects. If you do not understand the sensitivity of the risk results to this conservative assumption, you may misallocate your loss prevention resources or misinform your company or the public about the actual risk. 

The need for aggregate and cumulative non-occupational exposure assessments, and lower reference doses for all assessments, means that some pesticides will fail lower-tier risk assessments and without more refined exposure data they might even fail higher-tiered assessments. For example, in North America many of the residential uses of the OPs have been discontinued as a result of the aggregate risk assessments. As a result, there has been increased emphasis on gathering better toxicology and exposure data to reduce the conservatisms that are contained in the current system. 

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