Not all air pollutants are created equal, and a new study has found that coal reigns supreme as the most toxic to humans.

Research led by a team from the Langone Medical Center at NYU discovered that fossil fuel emissions – including diesel vehicles and coal-fired power plants – generated the most toxic particles. Exposure to tiny particles in fossil fuel emissions were in fact linked to increased death risk from heart disease.

The nationwide study published Dec. 2 in the journal Environmental Health Perspectives is the first of its kind and involved almost 450,000 subjects in 100 American cities from 1982 to 2004.

Lead investigator and epidemiologist Dr. George Thurston said their research disproves previous ones that assumed all tiny particles are equally toxic regardless of source.

“Our results indicate that, pound for pound, coal-burning particles contribute roughly five times as much to heart disease mortality risk as the average air pollution PM2.5 particle in the United States,” he warned.

Thurston illustrated this point by citing that in Phoenix, windblown dust particles are much less dangerous than coal-burning emissions in Pittsburgh, while urban vehicle traffic in LA creates emissions shown to have half of coal’s toxicity.

In addition, those from wind-blown soil and burning wood as well as other biomass emerged as “non-significant” in death risks. “In the Arab world, there are high levels of particle pollution, but they’re from windblown soil. You think those are the same as coal? They’re not,” Thurston explained.

The tiny particles typically composed of arsenic, mercury, selenium, and other toxins increase the risk for fatal heart and lung conditions as they are small enough to get past one’s bodily defenses and become absorbed into the bloodstream and the lungs.

The team used trace-element “fingerprints” to assess the contributions of various pollutant sources. For instance, traces of selenium and arsenic were found in coal burning, while carbon was aplenty in traffic emissions. The toxicities of the tiny particles, too, were dependent on chemical composition and source of pollution.

The World Health Organization estimated that around three million individuals die every year from matter found in air pollution.

The study results were considered relevant to the U.N. Climate Change Conference currently being held in Paris, where delegates are in talks to reduce greenhouse gas emissions.

Photo: Aske Holst | Flickr