Question

Lead in drinking water. The U.S. Environmental Protection Agency (EPA) sets a limit on the amount of lead permitted in drinking water. The EPA Action Level for lead is .015 milligram per liter (mg/L) of water. Under EPA guidelines, 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 (coauthor Sincich) received a recent 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.

Short answer

The water customers are not at risk of drinking water with unhealthy lead levels.

Step-by-step solution

Defining percentile

A percentile is a value below which a certain number or percentage of values or observations fall. For example, the 45th percentile indicates 45 percent of the total number of values or observations can be found.

Indicating the reason for not having a risk of drinking water with unhealthy lead levels.

The research study shows that 90 percent of the samples show that the lead concentration is 0.00372 mg/L (which is less than 0.15 mg/L). Due to this reason, the drinking water is safe for the water customers.