More than half a million single family homes and condos in New Jersey are sitting in high-risk ZIP codes, meaning at least one environmental factor is at hazardous levels, according to new research.

John Foxx, Getty Images

The report released Thursday by ATTOM Data Solutions, an online property database, analyzed 8,642 ZIP codes across the United States, including 348 in New Jersey that have sufficient housing trend data.

Twenty-five percent of single family properties in New Jersey were found to be in ZIP codes with high or very high risk for at least one of four environmental hazards: Superfunds, brownfields, polluters or poor air quality.

Based on the presence of each hazard, ATTOM gave each ZIP code a hazard index. The ZIP code 07105 in the city of Newark was New Jersey's worst. The report pointed to two Superfund sites on the National Priorities List, three brownfields and 13 industrial polluters.

Milford ZIP code 08848 in Hunterdon County pulled New Jersey's second-worst score with one Superfund site and an air quality risk considered "very high."

Check the heat map below to see how your city scored.

"Home values are higher and long-term appreciation is stronger in ZIP codes without a high risk for any of the four environmental hazards analyzed," said Daren Blomquist, senior vice president at ATTOM Data Solutions. "Corresponding to that is a higher share of homes still seriously underwater in the ZIP codes with a high risk of at least one environmental hazard, indicating those areas have not regained as much of the home value lost during the downturn."

In New Jersey, Blomquist said, the value of homes in ZIP codes with at least one high-risk factor is 15 percent below the average of homes with no nearby risk. A similar pattern exists for median sales prices.

New Jersey homeowners in low-risk environmental hazard areas who sold their home in 2016 gained an average of $35,000 since they purchased the property. In high-risk areas, the gain was $19,000.

"This is one thing your real estate agent may not tell you about, but you probably want to research before you buy a home," Blomquist said.

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Contact reporter Dino Flammia at dino.flammia@townsquaremedia.com.