Which contaminant is measured to assess the safety of drinking water related to health risks?

Measuring the safety of drinking water concerning health risks involves assessing a wide range of potential contaminants that can adversely affect human health. Bacteria, nitrates, and heavy metals are all significant concerns.

Bacteria in drinking water can lead to severe illnesses, particularly gastrointestinal diseases. Pathogens such as E. coli and Giardia are indicators of microbial contamination and pose direct health risks to consumers.

Nitrates are often a concern because they can originate from agricultural runoff, sewage, and fertilization practices. High levels of nitrates in drinking water can lead to methemoglobinemia, or "blue baby syndrome," which affects the ability of blood to carry oxygen in infants.

Heavy metals, including lead, arsenic, and mercury, can leach into water supplies from industrial discharges, corroded pipes, or natural sources. These metals are particularly dangerous as they can accumulate in the body and lead to chronic health issues, including neurological damage, developmental problems, and increased cancer risk.

Given that all three of these contaminant categories have well-documented health risks and are regularly monitored for safety in drinking water, it's clear that a comprehensive assessment of drinking water safety would indeed include measuring bacteria, nitrates, and heavy metals. Thus, the correct answer