Relationship between cause-specific mortality and temperature inversions in the Salt Lake Valley

During winter months the Salt Lake Valley can be covered by a thick dense fog, known as a temperature inversion, for a few days to several weeks. Cold temperatures remain trapped on the valley floor while warmer air circulates above the cold mass. This study examined the relationships between (a) air pollutants and temperature inversions and (b) cause-specific mortality and temperature inversions. No previous investigation of this type has been accomplished for Salt Lake Valley. This investigation will add to the understanding of air quality during temperature inversions and whether a mortality burden accompanies such events in the Salt Lake Valley. Daily data were collected on clearing index (a quantitative measurement for temperature inversion) and four major pollutants measured by the Bureau of Air Quality - Utah Department of Health from January 1, 1981 to December 31, 1983. During the same time period, mortality data were collected, from the Bureau of Vital Statistics Utah Department of Health, on all pulmonary or cardiovascular deaths. Of the four pollutants investigated, carbon monoxide was found to increase during temperature inversions. It was, however, difficult to determine how much influence this increase of carbon monoxide has on the health of individuals breathing the air during these inversions. Of greatest import to this investigation is the consistent relationship found between monthly mortality density ratios (greater than 1) and average monthly clearing index (less than 500 - indicative of a temperature inversion). Five of the 36 months demonstrated this relationship, whereas the remainder (31 months) had a mortality density ratio less than 1 and an average clearing index greater than 500. This relationship strongly implies cause-specific mortality is directly linked to temperature inversions or an entity of an inversion.