The city of Flint, Mich., is in the midst of a water crisis several years in the making. The city opted out of Detroit’s water supply and began drawing water from the Flint River in April 2014, part of a cost-saving move. Eighteen months later, in the fall of 2015, researchers discovered that the proportion of children with above-average lead levels in their blood had doubled.

The city reconnected to Detroit’s water system in October, but the damage was done. Water from the Flint River was found to be highly corrosive to the lead pipes still used in some parts of the city. Even though Flint River water no longer flows through the city’s pipes, it’s unclear how long those pipes will continue to leach unsafe levels of lead into the tap water supply. Experts currently say the water is safe for bathing, but not drinking.

A group of Virginia Tech researchers who sampled the water in 271 Flint homes last summer found some contained lead levels high enough to meet the EPA’s definition of “toxic waste.”

The researchers posted their test results online, which I represent graphically below with other visuals to help understand just how high above normal Flint’s lead levels really were.

Lead in water is measured in terms of parts per billion (ppb). If a test comes back with lead levels higher than 15 ppb, the EPA recommends that homeowners and municipalities take steps to reduce that level, like updating pipes and putting anti-corrosive elements in the water when appropriate.

But 15 ppb is a regulatory measure, not a public health one. Researchers stress that there is no 100 percent “safe” level of lead in drinking water, only acceptable levels. Even levels as low as 5 ppb can be a cause for concern, according to the group studying Flint’s water.

So let’s start with Flint’s neighboring cities. At the city level, public health officials are most concerned with the 90th percentile level of lead exposure in homes they test — that is, 90 percent of homes will have a lead level belowthis threshold, while 10 percent will register above it.

Leave a Reply

Your email address will not be published. Required fields are marked *