The quality of the air we breathe affects our health.
Exposure to high levels of air pollutants has been associated
with cardiovascular and respiratory diseases.
Levels of some kinds of air pollution, like soot, have come down a lot over the years
as a result of environmental protection policies, but levels of other pollutants,
like ozone, have not come down as much.
It's also been noticed that lung diseases associated
with smoking-like emphysema-are occurring in people who don't smoke.
Here in the US, researchers have been working to understand the relationship of air pollution
to health outcomes, including lung health and emphysema.
Emphysema is destruction of the air sacs of the lung, most often caused by smoking.
The amount of lung affected by emphysema can be measured on a CT scan
and is associated with lung function impairment.
This brings us to a study published in the current issue of JAMA.
Researchers used data from MESA, a community-based cohort study.
Participants between the ages of 45 to 84 were recruited starting
in 2000 and followed up through 2018.
These participants resided in 6 cities throughout the US - Chicago, Winston-Salem,
Los Angeles, Baltimore, St. Paul and New York.
All participants had a baseline cardiac CT scan,
and most had at least one if not several follow-up scans.
Exposure to four pollutants: Ozone, fine particulate matter, oxides of nitrogen,
and black carbon were estimated over the follow-up period using EPA data
to calculate annual mean concentrations for each pollutant correlated
with each participants' home address.
Using CT scans, the researchers measured change in percent of the lung affected
by emphysema up to 5 times per participant.
The also performed spirometry up to 3 times
on each participant to evaluate their lung function.
Just over 7000 participants were followed
for a median 10 years; 1/3 to 1/2 of them never smoked.
Median percent emphysema was 3% at baseline and increased a mean 0.58% per 10 years.
The authors found a statistically significant association
between baseline ambient concentrations of Ozone; Fine Particulate matter;
Oxides of nitrogen; and Black carbon and increases in progression
of percent emphysema over those 10 years.
What about exposure to pollution over time?
There, the authors found statistically significant associations between increases
in Oxides of Nitrogen and Ozone and progression in percent emphysema.
A 3 parts per billion-higher long-term mean ozone exposure over follow-up was associated
with an increase in progression of percent emphysema over 10 years,
equal to the association between 29 pack-years of smoking and emphysema progression.
In other words, if the ambient ozone level was 3 parts per billion higher over 10 years
where you live compared to another location, that's roughly the equivalent of smoking a pack
of cigarettes a day for 29 years.
And as we see in figure 2A, Ozone levels in some major US cities are increasing by that amount.
The good news is that during the observation period of this study,
long-term average concentrations of fine particulate matter and oxides
of nitrogen decreased, as in these two figures.
What about lung function?
Ozone concentrations at baseline
and over follow-up were statistically significantly associated with a faster decline
in FEV in the first second, or FEV1, which is a standard measure of lung function.
The authors conclude that long-term exposure
to ambient air pollution is significantly associated
with increased emphysema-like changes seen on CT scans,
as well as with declines in lung function.
To read the study, click the link in the description.