Car Exhaust, Grilling Generate Mutagenic Compounds Previously Unknown to Science

The chemical reactions that create car exhaust and grill marks on steaks produce previously unknown compounds that are hundreds of times more mutagenic than their parent compounds, which are known carcinogens.

Writing in the journal Environmental Science and Technology, Oregon State University chemistry and toxicology professor Staci Simonich and her colleagues report that the presence of these compounds raises concerns about the health impacts in heavily-polluted areas and certain dietary exposures.

"Some of the compounds that we've discovered are far more mutagenic than we previously understood, and may exist in the environment as a result of heavy air pollution from vehicles or some types of food preparation," Simonich said. Mutagens are chemicals that can cause DNA damage in cells that in turn can cause cancer.

"We don't know at this point what levels may be present, and will explore that in continued research," Simonich said.

Polycyclic aromatic hydrocarbons, or PAHs, are considered to be the parent compounds behind these chemical reactions. PAHs are formed as a natural result of almost every form of combustion, from wood burning in a fireplace to the internal combustion in an automobile engine.

An agency of the World Health Organization reported last fall that it now considers outdoor air pollution, especially particulate matter, to be carcinogenic. PAHs are of concern because they are one type of particulate matter found in air pollution.

PAHs are worrisome because many of them, such as benzopyrene, are known to be carcinogenic. When a PAH interacts with nitrogen and becomes "nitrated" they become NPAHs, which the researchers say are even more of a concern. The newfound compounds are all NPAHs that were unknown up until now, the scientists said.

"This study found that the direct mutagenicity of the NPAHs with one nitrogen group can increase 6 to 432 times more than the parent compound," OSU wrote in a statement. "NPAHs based on two nitrogen groups can be 272 to 467 times more mutagenic."

The researchers went on to say that these estimates may actually be understating the toxicity of these compounds.