RealtyTrac's hazardous zips, heat-mapped.

The recently released second annual Manmade Environmental Hazards Housing Risk Report from RealtyTrac revealed that 25 million U.S. homes are in zip codes at high risk or very high risk for manmade environmental hazards. That's 38% of the 64 million homes in the 7,751 zip codes analyzed.

The study looked at five different manmade environmental hazards, including air quality, superfund sites, polluters, brownfields and former drug labs.

Home prices see the consequences of these high risk zips. The median sales price of homes in high risk zip codes was $251,106 in 2015 on average, 15% lower than the median sales price of $295,202 for homes in zip codes with low or very low risk.

“Buying a home in an area with low risk of manmade environmental hazards may not just be a good idea for health and safety reasons; it may also be good for financial reasons,” said Daren Blomquist, vice president at RealtyTrac. “Across the country, home prices in high risk zip codes were lower on average, and appreciation over the last 10 years slower when compared to home prices and 10-year appreciation in low risk zip codes.”

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