More than 4 million Americans live in places where contaminants in drinking water exceed a legal limit—and poor, rural areas are often more affected than wealthy, urban and suburban ones. Those are some of the key takeaways from a new database that the Environmental Working Group (EWG) released today.

“We’re seeing a lot of problems in places that are more rural and lower income.”

The database pulls about 30 million records from 2010-2015, mostly from state agencies. With the handy tool,  you can enter your zip code and get a report on the contaminants that flow from your tap.

Although EWG has not yet analyzed all the data it collected according to demographics, it did find some preliminary patterns. “We’re seeing a lot of problems in places that are more rural and lower income,” said Bill Walker, vice president and managing editor of EWG. Walker emphasized that agriculture is one of the biggest pollutants of drinking water in the country and that, while pesticides and fertilizers are used in many places, toxic runoff from these pollutants are found at higher readings in rural communities.