Public Views on Drinking Water Standards as Risk Indicators

Government agencies often compare contaminant levels to standards and other regulatory benchmarks to convey relative risk to public audiences, as well as for enforcement. Yet we know little of how citizens interpret these risk indicators or factors influencing interpretations. Owners of private residential wells in New Jersey were surveyed by mail. A majority appreciated this comparison, trusted the standard, and could effectively compare the contaminant level to the standard. Most people who recalled that their own well water quality was unsatisfactory simply installed treatment systems. However, there was also a surprising amount of inability to tell whether pollution levels were better or worse than the standard, perhaps exacerbated by confusing institutional language to summarize the comparison (e.g., pollution “exceeds” or is “less than” the standard) and innumeracy. There was also substantial skepticism about the degree to which pollution levels below, or (to a lesser extent) above, the standard are harmless or harmful, respectively. Skepticism was variously due to distrust of standards, disbelief in thresholds for health effects, inability to accurately compare standards and contaminant levels, information processing, and demographics. Discontinuity in reactions below versus above the standard did not exist in the aggregate, and rarely among individuals, contrary to some previous findings. At identical standards and contaminant levels, familiar toxins (mercury, arsenic, lead) elicited higher risk ratings than less familiar ones. Given the wide institutional use of this risk indicator, further research on how to improve the design and use of this indicator, and consideration of alternatives, is warranted.