15.5  Case Study: Flint Water Crisis

Imagine you open the tap to get a glass of water. But instead of the clear water you’re used to, the water comes out looking brown and has an odor.^[1]  Would you want to drink this water? This is exactly what the residents of Flint, MI found in May 2014 when they used their tap water. The dirty water was the first evidence of the Flint water crisis. In this section, we’ll take a look at why it happened using the concepts from this chapter.

Lead Pipes

Lead has been used as plumbing material since ancient times.^[2]  In fact, the root word for plumbing is the latin word plumbum, meaning lead. Even though the ancient Romans valued lead as a versatile material, they also knew it could lead to health effects. These include symptoms such as high blood pressure; joint and muscle pain; and memory/concentration difficulties. And in children, exposure can lead to developmental delays and learning difficulties.^[3]

Although these health risks were known, lead pipes were widely utilized to supply water to homes until the early 20th century.^[4]  You can see an interactive map of the US here to see where these pipes are located. Since it is toxic, it is important to minimize leaching of the lead from the pipes into the water.

One way this is accomplished is by adding phosphate to the water.^[5]  This forms an anti-corrosion crust made of lead (II) phosphate.

In order to maintain the crust, the water flowing through the pipes must have phosphate continually added and maintained at a certain pH.

Water Source Switch

The water crisis in Flint, MI began in April 2014 when the city decided to switch its water supply to the Flint River that did not add phosphate.^[6]  Let’s now consider the effect of the absence of phosphate on lead levels.

In addition to the lead (II) phosphate, the protective crust also has lead (II) carbonate. Another factor in the lead level is the pH of the water. How does changing the pH affect the lead (II) carbonate portion of the protective crust?

Once the protective crust was gone, lead in the pipe was exposed. This exposed lead underwent ionization due to a process called corrosion, which will be covered in Section 17.6. The result of the change in phosphate concentration and the pH lead to an increase in lead levels to over 200 ppb (parts per billion).^[7]  That’s at least 13 times the EPA limit of 15 ppb. Some samples tested came in at 13,000 ppb!

Aftermath of the Crisis

The city of Flint switched their water supply back to Detroit Water (now called Great Lakes Water Authority) in October 2015. Although lead levels improved, it remained unsafe to drink at over 20 ppb in March 2016.^[8]

For some children, who are particularly vulnerable to the effects of lead exposure, it was already too late. Blood lead level testing found that the number of children under 5 with elevated lead level nearly doubled after the initial switch in water source.^[9]

Summary

This section reviewed a simple and innocuous seeming change in water sources lead to the Flint water crisis. Concepts from solubility and equilibria explain why it occurred. It also illustrates the vital role chemistry plays in our everyday lives whether we’re aware it or not. We’ll revisit Flint water crisis again in Chapter 17, when we consider how electrochemical reactions also played roles in this disaster.