In August, the Environmental Protection Agency took historic action to protect the public from a dangerous pesticide, issuing an emergency halt to the sale of a weed killer shown to cause irreversible damage to fetuses during pregnancy.

Emerging science shows the potential health risks tied to a wide range of pesticides that are routinely sprayed on U.S. land. Sometimes that spraying happens near schools where children, who are particularly vulnerable to those risks, spend their days.

Landscapes across America, from neighborhood playgrounds to school sports fields, are often coated in toxic chemicals. In fact, by some estimates, more than 1 billion pounds of pesticides are sprayed on U.S. lands every year and drift beyond their intended targets.

Maryland resident Ling Tan knows it well. She remembers smelling pesticides outside her home and worrying about her children, who have asthma. She felt like her kids could not escape the potential harm since they were also exposed to it at school and on playgrounds, in addition to the incidents in their neighborhood.

Children are more vulnerable to the effects of the poisons in pesticides, which can impact their developing brains, organs and immune systems.

Scott Faber, senior vice president of government affairs at the Environmental Working Group, or EWG, is part of an effort to better understand those effects.

EWG recently mapped thousands of elementary schools across America that could be in the path of agricultural pesticides.

Faber said the map of schools near crop fields was shocking to him.

EWG found more than 4,000 elementary schools located within 200 feet of a crop field where pesticides could be applied, leaving kids at risk of inhaling or ingesting the toxic drift.

It may not end there. According to the U.S. Geological Survey, pesticides can travel for hundreds of miles.

Protections in place vary from state to state.

California and Texas require the use of low-risk pesticides. Louisiana and Pennsylvania require schools to track students who are sensitive to pesticides, while Georgia and New Mexico limit the times when spraying can be done near schools.

There are no federal laws that address the spraying of pesticides near schools.

In the absence of federal laws, parents like Tan are pushing ahead. She and just a few other parents raised concern and got the first countywide ban of pesticides passed in the United States.

But she knows many communities are still unprotected.

“It’s really frustrating because as parents, we think that the federal government is not looking out for us,” Tan said. “We need to speak up instead of looking the other way.”