Does Air Pollution Cause Asthma?

by John Bottrell Health Professional

With asthma rates increasing, and pollution on the forefront of our minds, many of us like to blame pollution for the rise in asthma rates.
So is pollution
really the culprit, or is there something else going on?
Let's investigate.

The Environmental Protection Agency (EPA) recognizes two types of air pollutants that have been proven by various studies to affect asthma.
These are:

  • Ozone.
    This is a naturally occurring gas in the earth's atmosphere to protect us from the sun's ultraviolet rays.
    On the earth's surface it can mix with fumes from exhaust and can be harmful.
    It's levels are higher on hot summer days, and therefore kids are more at risk because they tend to spend more time outside.
    It's found mainly in smog.

  • Particle matter:
    These are tiny particles suspended in the air we breathe. This can be naturally occurring, such as from volcanoes, dust storms, fires, sea spray. It can also be man made, such as burning fossil fuels, power plant and industrial plant aerosols. Man made aerosols account for 10% of air pollution.

This is found in haze, smoke and dust.

According to a report by the EPA for healthcare professionals,
air pollutants trigger asthma because they injure the airway, cause inflammation, and increase airway reactivity to asthma triggers such as dust mites, molds, pollen and cockroach urine.

I believe the EPA here because I've seen the studies.
In fact, the latest study released shows a strong correlation between uncontrolled asthma and ozone and particulate matter pollution, according to, "Years of Air Pollution May Be Tied to Uncontrolled

Researchers studied five cities in France between 2003 and 2007 and concluded that "the risk of uncontrolled asthma was 69 percent higher among those with long-term exposure to ozone and 35 percent higher for those with long-term exposure to particulate matter."

Pollution looks like it might trigger asthma, and it may even make asthma worse. Yet does it cause

Asthma researchers have surmised that constant exposure to any irritant that causes airway inflammation may result in chronic (it's always there) inflammation -- which is asthma.
So can we now assume short term exposure to pollutants may trigger asthma, and long-term exposure may cause asthma.

So it only makes sense that pollution should be blamed for rising asthma rates. Right?
Well, you'd think so, except for one important statistic that often gets ignored: pollution rates are on the decline, yet asthma rates have stayed the same or risen. So what's the deal?

Pollution is still considered to be a
major contributing factor to rising asthma rates in Western societies such as the U.S., U.K, and Australia.
Yet new evidence shows
asthma rates continue to rise (up 4.3 percent since 2001) "despite improved air quality throughout most of the country and widespread decreases in smoking," the LA Times reports.

Some asthma experts believe this might be proof something besides air pollution is causing asthma, like the
hygiene hypothesis or
microflora hypothesis.

I think we can safely conclude here that pollution is definitely an asthma trigger, yet whether it's a cause is still open to debate.

However, based on my own research,
asthma has many causes
-- air pollution included.
This is my theory; my educated guess.
What do you think?

John Bottrell
Meet Our Writer
John Bottrell

John Bottrell is a registered Respiratory Therapist. He wrote for HealthCentral as a health professional for Asthma and Chronic Obstructive Pulmonary Disease (COPD).