Drinking Water: Measures and Data
Why are drinking water contaminants a concern?According to state statistics, the most commonly occurring contaminants in Washington’s drinking water are nitrate and microorganisms (such as bacteria and viruses). Infants, children, the elderly, and those with weakened immune systems are particularly susceptible to serious health effects from these contaminants. Although public water systems must regularly test for dozens of potentially harmful contaminants, there is no statewide testing required for private wells. Incomplete information about exposure to water-related health problems hampers epidemiological inquiry.
How are they tracked?The state tracks waterborne disease outbreaks. However, for various reasons, reports of outbreaks are rare and may not reflect the actual extent of waterborne illness issues. Group A and B public water systems must regularly test their water and meet federal and state requirements designed to protect people from waterborne illness. Results of these tests are compiled by the state. Measures of the presence and concentration of contaminants in drinking water are useful for estimates of risk.
What can be done?The proportions of public water systems that conduct all required tests for microbiologic contamination and for nitrate are used as protective indicators for risk. Other indicators that ensure safe drinking water include the proportion of systems with current inspections, operating permits in full compliance, and fully certified system operators. Additional indicators, useful as proxy estimates of risk, that can be derived from drinking water data include hazard indicators (e.g., the proportion of public water supplies not meeting microbiological standards) and health outcome indicators (e.g., the number of waterborne disease outbreaks).
More Information on Specific Contaminants