As a child, I thought anybody who refused to drink tap water was just too picky. But once you learn about the array of potentially harmful chemicals in U.S. tap water, you realize it’s smart to protect yourself and your family.

Tap water from almost all public water utilities in the country meets federal standards. But compliance with legal standards isn’t the same as being free of pollutants. In fact, the tap water in many communities can contain contaminants at levels scientists don’t consider safe.

Sure, it’s unlikely you’ll have to call in sick the day after brewing your morning coffee with unfiltered tap water. But over time, the risks of exposure to even low levels of contaminants can add up. And in many communities, especially small ones, tap water contaminant levels can be quite high.

An EWG investigation reveals that atrazine, a heavily used weed killer sprayed primarily on corn, contaminates drinking water in many parts of rural America. Atrazine is sprayed in late spring and early summer, and it runs off corn fields into streams and reservoirs.

In 2015 the weed killer was detected in the tap water of nearly 30 million Americans during the spraying season. Atrazine, like many toxic chemicals, poses particular risks to the developing fetus. So for expectant parents who want to do everything possible to ensure the health of their baby, these findings are a call to action.

Atrazine disrupts hormones and harms the developing fetus. It can even turn developing male frogs into egg-laying females. Although atrazine in drinking water is regulated by federal law, these harmful effects have been seen at levels much lower than the federal limit of 3 parts per billion. (A part per billion is about one drop of water in an Olympic-size swimming pool.) In recent studies, pregnant women who drank water contaminated with atrazine were more likely to have premature or low-birth-weight babies. Low birth weight increases the risk of health problems later in life, such as breathing problems, developmental delays and cardiovascular disease.

We found that atrazine levels spike far above the legal limit in spring and summer, when atrazine is heavily used. In the water supplies we investigated, some of these spikes were as much as three to seven times the legal limit. Spikes often go unreported, because utilities aren’t required to test their water when the atrazine levels are high, so many do it before or after the spike.

What can you do?

EWG has tools and information to help you take action to protect your family and children in just a few simple steps.

First, find out whether your water contains atrazine or other contaminants. You won’t be able to see, smell or taste it, so search the EWG Tap Water Database to see if it’s been found in your drinking water.

Have a private well? Even private water supplies in corn-growing areas can be contaminated. We suggest that pregnant women with private well water, especially those in agricultural areas, seek out a state-certified water testing laboratory to test for atrazine and other potential contaminants.

Atrazine is only one possible component of the toxic cocktail in your water, each with its own side effects and health consequences. Children are particularly vulnerable to the toxic effects of these contaminants. That’s why it’s so important to filter them out of your water and minimize seasonal atrazine spikes.

To do this, you can use a carbon filter such as an inexpensive countertop pitcher or faucet-mount filter. EWG’s Water Filter Guide can help you identify available options for water filters.

Keep in mind that the level reported by your water utility may not be the highest one you’ve been exposed to. Whether you’re pregnant or planning on becoming pregnant, a water filter is key to protecting the fetus – because as it turns out, all those “picky” people may have been right all along.

Access to clean, safe tap water is one of America’s greatest resources, and it’s important to protect it. Please add your name to EWG’s petition urging the Environmental Protection Agency to ban atrazine.