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Guide PHIT Data: Lead in drinking water

This dataset shows drinking water exceedances for lead by Community Water System and year of exceedance. An exceedance is a measured concentration higher than 15 ug/L in drinking water.

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What you need to know

Drinking water violations are determined by the Massachusetts Department of Environmental Protection from compliance water sampling. Each row represents a water sample that tested above the EPA Action Level (AL) of 15 ug/L. The AL is compared to the 90th percentile value of all sampling results collected during each monitoring period. (This means that the sample exceeds the action level if more than 10 out of 100 samples taken exceed 15 ug/L.) 


Each record also contains descriptive information about the Community Water System, including the city/town served, number of people served, the community population, and the percent of the community population served by the Community Water System.

Explore lead in drinking water data

This dataset provides information on the number of Community Water Systems and the number of people potentially exposed to lead at different concentrations above the exceedance level. Maximum concentrations provide information on the peak potential exposure to lead by Community Water System, a small geographic scale.

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Information about these data

Lead exceedance data are published for Community Water Systems only. Private wells and transient non-community water systems may also be an important source of exposure. These data should not be used to identify single problematic water systems. To identify regulatory or compliance issues with single water systems contact the MA DEP.  Multiple Community Water Systems can serve the same city/county and multiple cities/counties can be served by a single Community Water System. Measures do not account for the variability in sampling and numbers of sampling repeats. Furthermore, concentrations in drinking water cannot be directly converted to exposure because water consumption varies by climate, level of physical activity, and between people.  Due to errors in estimating populations, the measures may overestimate or underestimate the number of affected people.

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