Almost half of Americans breathing more unhealthy air than ever before: Report

Almost half of Americans are experiencing more days of unhealthy and hazardous air quality than before, according to a report by the American Lung Association.

Almost half of Americans -- 137 million people -- are experiencing more days of "very unhealthy" and "hazardous" air quality than in the previous two decades combined, according to a report published this week by the American Lung Association.

The annual "State of the Air" report looked at Americans' exposure to two types of air pollution: ozone, also known as "smog," and particle pollution, also known as "soot." It found that over 63 million Americans are now impacted by deadly particle pollution, an increase of nearly 9 million people from previous years.

This particle pollution or "particulate matter" comes from wildfires, wood-burning stoves, coal-fired power plants and diesel engines, and can cause multiple health problems, including asthma attacks, heart attacks and strokes. With repeated exposure, it can cause lung cancer.

"We've seen much better air quality in most areas today than when we started the report. But over the last five years, we've seen an uptick, and we attribute a lot of that to climate change. We've had some of the hottest years on record -- creating dry conditions that lead to drought and wildfires," said Paul Billings, senior vice president of public policy for the American Lung Association.