Elemental analysis of airborne particulate matter and cooling water in west Texas residences

Ten residences in El Paso, TX were monitored in the summer of 2001 for concurrent indoor and outdoor PM2.5 and PM10 10-min mass concentrations in an attempt to establish the indoor–outdoor PM correlation for typical west Texas residences equipped with evaporative coolers. Simultaneously, the modified tapered element oscillating microbalance instruments were used to collect 48-h PM2.5 and PM10 samples, both indoor and outdoor, for elemental analysis. Water samples were also taken at each home for chemical and PM correlation analysis. The air and water samples were analyzed by inductively coupled plasma–mass spectrometry, with 30 elements identifiable above detection limits in the outdoor PM10 samples and fewer elements in the PM2.5 and indoor PM10. Indoor elemental concentrations in PM10 were found to be approximately 50–70% lower than outdoor concentrations in nine of ten homes, consistent with the PM10 indoor/outdoor (I/O) mass concentrations previously reported. PM2.5 I/O ratio correlations were not as strong as for PM10; however, reduced correlations could be attributed to a pattern of recurring outlier data pairs, consisting of the same three or four elements in all ten homes. Comparison of the elemental concentrations of the evaporative cooler supply water and indoor PM demonstrated little or no correlation, yielding a conclusion that the evaporative cooler was not introducing dissolved solids from the supply water into indoor air. Overall, evaporative cooling appears to provide a cleansing of indoor air.