A rural community water supply contaminated by wastes from a railroad derailment has a hazard index for adults greater than one but less than one for children. How should the exposure be characterized?

• A. there is no significant risk to the community
• B. there is an unacceptable risk to adults but not to children
• C. there is an unacceptable risk to children but not adults
• D. there is an unacceptable risk to both adults and children

Answer: (B)

When evaluating non-carcinogenic risk, the hazard index (HI) compares exposure to a reference dose. If HI exceeds 1, adverse health effects are potentially unacceptable for that group; if HI is below 1, the risk is considered acceptable. In this scenario, adults have a hazard index greater than 1, indicating an unacceptable risk for that group. Children have a hazard index less than 1, indicating no unacceptable risk for them. Thus the exposure is characterized as an unacceptable risk to adults but not to children. Differences in HI between groups can arise from factors like varying water consumption relative to body weight, which can shift the overall risk assessment between adults and children.