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Study: air pollution along Utah’s Wasatch Front causes more than 200 pneumonia cases each year

Air pollution trapped along the Wasatch Front by winter inversions is estimated to send more than 200 people to the emergency room with pneumonia each year, according to a study by University of Utah Health and Intermountain Healthcare. Bad air quality especially erodes the health of adults over age 65, a population particularly vulnerable to the effects of pneumonia. The research findings were published online in the Annals of the American Thoracic Society.

The Wasatch Front—a metropolitan region in north-central Utah—is mostly surrounded by mountains. During the winter months, Utah’s Wasatch Front experiences periodic weather inversions that trap emissions along the metropolitan valley. Within days, air pollution worsens as the concentration of small particles rises, at times turning the air into the dirtiest in the country.

The research team applied time-stratified case-crossover analyses with distributed lag to 4336 pneumonia cases presenting to 7 emergency departments (EDs) over 2 years. They compared levels of PM2.5, NO2 and O3 at patient residences to ED cases, hospitalizations, objectively defined severe pneumonia, and mortality. They then calculated direct cost impacts of PM2.5 reduction.

Beginning one day after air quality deteriorates, increasing numbers of people end up in the hospital with pneumonia. The increase in cases from a single day of poor air quality can last up to a week.

Among adults ≥ 65 years old, the team found consistently positive associations between PM2.5 within 6 days of presentation and instances of pneumonia (lag-day-1 aOR 1.35 per 10 μg/m3 over 12 μg/m3, CI 1.16 – 1.57), severe pneumonia (lag-day-1 aOR 1.38, CI 1.06-1.80), and inpatient mortality (lag-day-5 aOR 1.50, CI 1.03 – 2.16).

Smaller associations were found between NO2 exposure and pneumonia occurrence, severity, and inpatient and 30-day mortality.

Ozone exposure was modestly associated with increased instances and severity of pneumonia in younger adults. PM2.5 and NO2 effects were greatest in colder months, and O3 in warmer months.

The team concluded that reduction of PM2.5 levels to < 12.0 mg/m3 could prevent 76-112 cases of pneumonia per year in these hospitals serving approximately half of the Wasatch Front’s population, reducing direct medical facility costs by $807,000 annually.

When exposed to elevated levels of particulate pollution, older adults are more likely to get pneumonia, be hospitalized with severe pneumonia and also die from pneumonia in the hospital.

—lead author Cheryl Pirozzi, M.D.

The relationship of air pollution to the severity of pneumonia was particularly striking. These are not just theoretical risks, but are important events for real members of our community. This study also shows just the tip of the iceberg of the costs we in Utah bear as a result of air pollution.

—co-author Robert Paine, M.D.

When levels of PM2.5 are less than 12 µg/m3, air quality is categorized as “good”. During a typical inversion air pollution episode, PM2.5increases to more than 40 µg/m3, categorized as “unhealthy for sensitive groups”. During these episodes, older adults are approximately 2.5-times more likely to have pneumonia, 2.5-times more likely to have severe pneumonia and triple their likelihood for dying in the hospital with pneumonia, says Pirozzi.

The extent of the findings surprised us. We were not expecting as large of a signal as we found.

—senior author Nathan C. Dean, M.D.

The study was supported by the Intermountain Research and Medical Foundation and an award from Veterans Affairs Health Services Research and Development.


  • Cheryl S Pirozzi, Barbara E Jones, James A VanDerslice, Yue Zhang, Robert Paine III, and Nathan C Dean (2017) “Short-Term Air Pollution and Incident Pneumonia: A Case-Crossover Study” doi: 10.1513/AnnalsATS.201706-495OC


Earle Beach

Another instance of VA-funded research that confuses correlation with causation.

When an inversion layer keeps nasty things in the air longer those nasty things have a greater opportunity to make people sick. Sounds good so far. Where this falls apart is when it is assumed that the nasty things are pollutants. Pneumonia is usually caused by viruses, bacteria, or fungi. Unless a mechanism can be established that these biological baddies hitch rides from the PM and don't just get breathed in by their lonesome there's no sound basis to assume causation.

Even were such to be established would it contribute as much to an increase in pneumonia cases as hospitals with their filtered air?



Pneumonia is an inflammatory condition of the lung with various causes. While the air pollution alone will not cause the common bacterial pneumonia, it will certain cause irritation of the lungs along with other problems. I live in the Wasatch Front and there are days where the air cause my eyes to burn and probably makes it harder to breathe.

Aaron Turpen

More proof that Utah is the promised land.

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