Where do our top air pollutants come from?

Most think of cars and industry as the sources of our air pollution, but the top polluters have changed over the years, scientists say, thanks to some tighter regulations.

Keeping tabs on air quality has been an important project for scientists for decades as poor air quality can lead to various health issues, including heart attacks, strokes and asthma attacks, according to the Puget Sound Clean Air Agency.

Most think of pollution coming from car exhaust or industrial production, and they would be right. Wood smoke from either wildfires or home fireplaces can also contribute to degraded air quality due to increased tiny particles in the air. 

Air quality managers monitor six common air pollutants: particle pollution, ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead, with the first two comprising the bulk of pollutants.

But the sources of our air pollution have changed over the years, scientists say, thanks to tighter regulations.

"I would say 20 years ago, the top three (air quality polluters) were transportation/motor vehicles, power generation and industry," says Prof. Joost de Gouw with the Chemistry Department at the University of Colorado. 

But the Clean Air Act, passed in 1970 and amended in 1977 and 1990, has reduced pollution from those sources.

"And so now other sources that haven't been addressed so much are coming to the top of the list," de Gouw says. Many of those are chemical products we use every day and their manufacturing processes.

"For instance, all the shampoos and deodorants that we use in our daily lives; all the bottles we have in our homes that come from the automotive shop, the grocery store and the garden store, basically," he said. 

And even agriculture can contribute to air quality issues.

"There's a lot of ammonia that comes from animal feedlots," de Gouw said. "We smell those here on a regular basis in Colorado. And so, yeah, so the number of sources has really diversified because we've been so successful in skimming off the top ones, you might say."