This is an archived article that was published on sltrib.com in 2017, and information in the article may be outdated. It is provided only for personal research purposes and may not be reprinted.
Think of poor air quality in Salt Lake City, and you likely think of winter temperature inversions and associated particulate matter (PM) pollution. Temperature inversions are a function of our topography with the Wasatch and Oquirrh mountain ranges to the east and west of the Salt Lake Valley. With 80 percent of Utah's population (and their associated motor vehicles) living and commuting between Ogden and Provo, the resultant tailpipe emissions, along with other air pollution sources, get trapped under a lid of warm air.
In the summer, residents of Salt Lake City and surrounding communities suffer from other forms of air pollution – predominantly smoke, dust and ozone. Smoke from forest fires and blowing dust cloud the sky, reminding us of the dry (and potentially volatile) desert conditions in which we live. From a health perspective, smoke can be especially problematic for people with lung conditions such as asthma or chronic obstruction pulmonary disease (COPD) or emphysema, and for people with heart conditions like congestive heart failure and angina. Windblown dust can also cause unhealthy levels of airborne particulate matter. Blowing dust is often a consequence of high winds and ambient dry conditions. However, man-made dust sources from development and construction are increasingly adding to environmental dust levels. Like smoke, dust can trigger adverse health events amongst those with underlying heart and lung disease.
Unlike smoke and dust that can be seen and/or smelled, and as such avoided, ground level ozone is colorless and odorless. Ground level ozone, in contrast to the "ozone level" which lies about 10 miles above the Earth's surface, is another form of air pollution. Ozone pollution is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight. Similar to particulate matter pollution, the major sources of NOx and VOC are motor vehicle and industrial emissions. Exposure to ozone pollution harms healthy people as well as those with chronic heart and lung disease. Long-term exposure to ozone not only aggravates underlying asthma, but is also a known cause of asthma; and is independently associated with premature death.
Ozone is measured at air quality monitors across the state. Ozone levels are reported as ppm (parts per million) and then associated with the AQI (Air Quality Index). Ozone levels of 0.054 ppm correlate with an AQI of 50. A value less than 50 is considered healthy of for all. AQI values between 51 and 150 should prompt sensitive people to avoid prolonged exposure or heavy exertion outdoors. AQI values in excess of 150 are unhealthy for everyone – a good day to exercise indoors! Recent hot, sunny days in Salt Lake City have resulted in ozone levels in the unhealthy level.
Since ozone peaks in mid-afternoon, runners and cyclists should enjoy outdoor exercise early in the day, or later in the evening — likewise people with underlying health conditions that enjoy a walk around the park or their neighborhood. Unfortunately, facemasks do not meaningfully reduce ozone exposure, so modifying outdoor activity is the best strategy to avoid short and long term exposure. You can check your local ozone level online at http://www.air.utah.gov, or download the app airnow.gov to your smart phone. Finally, we can all reduce ozone pollution by decreasing motor vehicle travel (combining trips, car-pooling, and avoiding idling); as well as switching to an electric lawn mower, eliminating outdoor fires, and limiting outdoor grilling when ozone levels are high.
Elizabeth Joy, M.D., MPH, is medical director for community health and food and nutrition at Intermountain Healthcare and an adjunct professor of family and preventive medicine at the University of Utah School of Medicine.