If you've been following the news coming out of Flint, Michigan, you're probably horrified for the residents there.

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If you’ve been following the news coming out of Flint, Michigan, you’re probably horrified for the residents there. In September, a local hospital released data showing that the percentage of children with elevated lead levels in their blood had doubled (and in some areas tripled) after the city switched water suppliers in April 2014. State officials initially dismissed these findings, but declared a public health emergency a week later.

Flint has switched back to its original water source, but experts say the crisis isn’t over: There are still questions about water safety, and it’s likely that the city’s youngest citizens will face cognitive and developmental challenges as a result of lead poisoning over the previous year and a half.

The “manmade disaster,” as Flint Mayor Karen Weaver called it, has also raised questions about lead exposure and water safety across the country—something many of us take for granted. Here’s a run-down of what exactly happened in Flint, and what you should know about your own water supply.

What is lead poisoning?

Lead is a metal that occurs naturally in the environment. Before it was phased out in the 1970s and 1980s, it was used regularly in household paints, gasoline, and plumbing materials like pipes, fixtures, and soldering.

Exposure to lead can be harmful for people of any age, but it’s especially dangerous for children and unborn babies, whose brains and nervous systems are still developing. Even at low levels, exposure to lead over time can contribute to behavior and attention problems, reduced IQ, low appetite and energy, kidney problems, and stunted growth. For the most part, these effects are irreversible and untreatable.

According to the U.S. Environmental Protection Agency (EPA), the most common source of lead poisoning in the United States is from dust and paint—but as much as 20 percent or more of exposure to lead can come from drinking water.

How does lead get into water?

Drinking water doesn’t usually contain lead at its source, but it does often travel through municipal and household plumbing systems made with lead. This in itself isn’t necessarily a problem; if water isn’t too corrosive, it can flow through these pipes without picking up significant traces of the toxic metal.

The EPA confirms that city plumbing is “the most likely source” of lead in Flint’s drinking water. “Like many older cities in the U.S., Flint, Michigan has a large number of lead pipes in their drinking water distribution system,” says Peter Grevatt, director of the agency’s Office of Groundwater and Drinking Water.

In Flint—a city on the verge of economic collapse—a decision was made to save money by switching from Detroit’s water system, which draws from Lake Huron, to the Flint River. But water from the Flint River is 19 times more corrosive than Lake Huron water, according to recent tests performed by Virginia Tech researchers.

There are ways to reduce water's corrosiveness—like adding chemicals called organophosphates—but in Flint, these measures were not required by the state, and were never put in place. (Another test by the Virginia Tech scientists found that these chemicals may not have made much of a difference in this case, anyway.) “U.S. EPA has formed a Task Force that is working with the City of Flint and the State of Michigan to ensure that optimal corrosion control is reestablished in Flint as quickly as possible,” says Grevatt, “and to ensure that this never happens again.”

How do I know if my water is safe?

According to EPA data, more than 91 percent of U.S. residents are served by public or community water systems that meet all applicable health standards, and more than 99 percent of all public water systems are in compliance with treatments designed to prevent exposure to lead and copper. Most public drinking water systems are required to monitor for the presence of lead, and are required to alert their customers of any concerns.

“However, everyday activities may impact the quality of the water you drink,” Grevatt cautions. “EPA encourages consumers to get familiar with their annual water quality report delivered by community water systems to their customers.”

This report, called a Consumer Confidence Report (CCR), is required to be distributed to customers by July 1 every year, usually with their water bill. It includes information on where your water comes from, your supplier’s compliance with drinking water rules, and levels of any contaminants detected in the last year—as well as their potential health effects. If you haven’t seen a recent report, you can find contact information for your local supplier at epa.gov/ccr.

If your water comes from a private well, the EPA recommends having your water tested for contaminants that might be present in your area. You may also want to test the water in your home if you have old pipes or plumbing fixtures, if there is an unexplained illness in your family, or if you notice a change in color, taste, or clarity of your water. (You cannot see, taste, or smell lead in drinking water, but other harmful chemicals could be to blame.)

“Testing is the only way to confirm whether an individual home has lead in their drinking water,” says Grevatt. Your county health department may be able to perform certain tests, or you can find a a state-certified laboratory by calling the EPA’s Safe Drinking Water Hotline at 800-426-4791.