SALEM, Ore. -- Your driveway could be making you sick. A new study by Oregon State University found products used to seal driveway surfaces could increase your risk of cancer.

Instead of re-paving, parking lots and driveways are often repaired with a much less expensive sealant or sealcoat.

The two most common kinds are a coal-tar-based sealant and one that's asphalt-based.

Recent U.S. Geological Survey studies have shown that coal-tar-based sealants contain hazardous chemicals that have been linked to cancer.

But a brand new study led by Oregon State University environmental chemist Staci Simonich discovered the sealants are even more hazardous than any previous study found.

"We measured the coal-tar sealcoat and found there were more chemicals that were toxic present in it than previously known," Simonich said.

The coal-tar sealcoat is commonly used in the Midwest and Eastern United States.

In the West, including in Oregon, the asphalt-based option is primarily used.

But Simonich says her research showed that while the asphalt sealant is much less toxic than the coal tar, there is still some risk.

"The asphalt also has some toxicity and contains many of these similar compounds, so there's not zero risk with the asphalt-based, it's just less than the coal-tar-based," she said.

Researchers have studied the effect of the chemicals on zebrafish, which are biologically similar to humans. They found the chemicals caused deformities in the fish.

Washington was the first state in the country to ban coal-tar-based sealant.