Surprising Water Samples

The Flint water crisis is a public health crisis that started in 2014 after the drinking water for the city was contaminated with lead.^[1] During that event, the city of Flint switched water sources, and the residents began to suspect that their water was contaminated with lead. The Michigan Department of Environmental Quality (DEQ) claimed that the water was compliant with federal regulations and that there was not a contamination problem. The federal guidelines for water safety state that a city is compliant if at least [latex]90\%[/latex] of water samples obtained from residences have lead in the water under [latex]15[/latex] parts per billion (ppb). A water sample is “contaminated” if it contains lead at [latex]15[/latex] ppb or above. In other words, under [latex]10\%[/latex] of residences would need to be contaminated in order for the city to be compliant.

The residents of Flint suspected that more than [latex]10\%[/latex] of the homes in the city had contaminated water, so they took their own sample of residences with support from scientists at Virginia Tech. They tested the water from [latex]271[/latex] homes as part of the Flint Water Study (FWS), and they recorded the proportion of homes that had contaminated water.