Priority setting for risk assessment--the benefit of human experience.
The chemical risk assessment process plays an essential role in the potential human health risk evaluation. Setting priorities for this purpose is critical for better use of the available human and material resources. It has been generally accepted that all new chemicals require safety evaluation before manufacture and sale. This is a difficult task due to the large number of chemicals directly consumed by man, as well as those that are widely used. At present, more than 50% of chemicals do not have the minimum data requirements for risk assessment. Production and release volumes are well-established prioritization criteria, although volume itself does not directly reflect the likelihood of human exposure. This quantitative approach applied in setting priorities may be influenced by human experience. Human data provided by epidemiological investigations have been accepted as the most credible evidence for human toxicity although analytical studies are expensive and require long-term follow up. Unfortunately, some epidemiological studies continue to have difficulties with exposure documentation, controlling bias and confounding, and are not able to provide predictions of risk until humans are exposed. Clinical toxicology services and Poison Centres around the world accumulate a great amount of toxicological-related information that may contribute to the evidence-based medicine and research and so collaborate with all the risk assessment disciplines. The information obtained from these services and centers has the potential to prioritize existing chemical assessment processes or to influence scheduling of classes of chemicals. Prioritization process may be improved by evaluating Poisons Centres statistics about frequency of cases, severity of effects, detection of unusual circumstances of exposure, as well as vulnerable sub-populations. International efforts for the harmonization of these data offer a useful tool to take advantage of this global information. Case report and case series may give information about the spectrum of human health effects, particularly when frequency is not very high. Improvement in the access to this information could be facilitated by better documentation of cases and targeted follow up. Special attention should be given to strengthen the documentation capabilities of clinical toxicologists, occupational physicians, and forensic toxicologists from developing countries. The benefit of human experience on priority setting for risk assessment purpose depends not only on the quality of information but also on the improvement of understanding between risk assessors and clinical toxicologists or poison center specialists.