SHOW WORK Lead in drinking water. The US. Environmental Protection Agency (EPA)
ID: 3299043 • Letter: S
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SHOW WORK
Lead in drinking water. The US. Environmental Protection Agency (EPA) sets a limit on the amount of lead permitted in drinking water. The EPA Action Level for lead is .015 milligrams per liter (mg/L) of water. Under EPA guide lines, if 90% of a water system's study samples have a lead concentration less than .015 mg/L, the water is considered safe for drinking. I (co-author Sincich) received a report on a study of lead levels in the drinking water of homes in my subdivision. The 90th percentile of the study sample had a lead concentration of .00372 mg/L. Are water customers in my subdivision at risk of drinking water with unhealthy lead levels? Explain.Explanation / Answer
The 90th percentile is the value for which 90% of the data points are smaller. Therefore the 90th percentile value of 0.00372 mg/L means that 90% of the sample values would have a concentration less than 0.00372 mg/L which automatically means that 90% of the sample values would have a concentration less than 0.015 mg/L because 0.015 > 0.00372. Therefore the water customers are safe as the requirements of EPA guidelines are clearly met such that 90% of the samples have a lead concentration of less than 0.015mg/L
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