The Combined Effect of Ambient Ozone Exposure and Toxic Air Releases on Hospitalization for Asthma and Respiratory Illnesses in Harris County, Texas

Nnamdi C Nnoli, The University of Texas School of Public Health

Abstract

This study represents an analysis of the effect of exposure to ambient ozone and toxic air releases on hospitalization for asthma and respiratory illnesses in Harris County, Texas from 2009 to 2013. Although the adverse health effects of ozone and air toxics have been documented in the literature, evidence regarding the respiratory health effects of these pollutants in Harris County, Texas, is limited. A study of this relationship in Harris County is particularly important due to its high levels of ambient ozone; an extensive network of air pollution monitoring systems; a cluster of petrochemical industries; the high levels of industrial emissions resulting from the large network of industries along the Houston Ship Channel; and the potential air pollution due to the large road network and vehicular traffic in the region. ^ Our study identified temporal and spatial variations in asthma hospitalization across the study region, and explored the combined effect of exposure to ambient ozone and air toxics on asthma and respiratory illnesses. A variable was created for seasons of the year, and analyses were performed separately for selected pulmonary irritants, and for all chemical pollutants. We used the ArcGIS tools and SAS 9.4 to perform spatial and statistical analysis respectively. Average maximum 8-hr ozone concentrations per zip code were interpolated using kriging to predict ozone measures in zip codes without ozone monitors. Our spatial analysis showed that asthma and Chronic Obstructive Pulmonary Disease (COPD) hot spots and clusters were located in zip codes that are relatively closer to zip codes of facilities with high toxic air releases and emission events located around the Houston ship channel area. ^ Asthma and COPD hospitalization rates per 10,000 people were determined to be highest in either first or fourth quarter of each study year from 2009 to 2013. Bivariate analysis using the Generalized Linear model found that asthma hospitalization rate per 10,000 people was significantly associated with total air releases reported under the Toxic Release Inventory (TRI) , as well as a combination of TRI total air releases and toxic emissions events air releases reported by the Texas Commission on Environmental Quality(TCEQ) in children 17 years and younger. Using zip codes that reported zero emissions as reference, asthma hospitalization rate per 10, 000 people was estimated to be 0.29 and 0.33 units higher when zip code levels of TRI toxic air releases, as well as combined TRI toxic air releases and TCEQ toxic emission events releases in pounds were 0–40 and 40–400, with p-value of 0.03 and 0.02 respectively for the selected pulmonary irritants. Similarly, asthma hospitalization per 10,000 people in children 17 years and younger was estimated to be 0.32 and 0.35 units higher when TRI toxic air releases, as well as combined TRI toxic air releases and TCEQ toxic emissions events release levels per zip code were above 400 lbs. with p-values of 0.03 and 0.01 respectively for the selected pulmonary irritants. Statistically significant results were also obtained for all released chemical pollutants. ^ In adults 18 years and above, a statistically significant effect was only observed when the levels of the selected air toxics were at the highest categorization (above 400lbs). Asthma hospitalization per 10,00 people in adults 18 years and above at this pollutant level was estimated to be 0.29 and 0.33 units higher with p-values of 0.008 and 0.02 respectively in zip codes with reported TRI toxic air release as well as combined TCEQ toxic emission events release and TRI toxic air releases respectively, for the selected pollutants . At pollutants levels above 400 pounds, statistically significant results were also obtained for all released chemical pollutants. Black race, average income per household, and season were significantly associated with asthma hospitalization in both children and adults. ^ In an adjusted regression controlling for our covariates, only season became a significant predictor (p<0.0001) of asthma and COPD hospitalization in both adults and children. An examination of the combined effect of ozone and toxic air releases showed that there is no significant interaction between the two variables relative to asthma and COPD hospitalization in both children and adults. We conclude that the major predictor of asthma and COPD hospitalization is season, with hospitalization rate per 10,000 people for asthma and COPD being highest in winter period when ozone levels are usually lowest.^

Subject Area

Environmental health|Health sciences|Environmental science

Recommended Citation

Nnoli, Nnamdi C, "The Combined Effect of Ambient Ozone Exposure and Toxic Air Releases on Hospitalization for Asthma and Respiratory Illnesses in Harris County, Texas" (2017). Texas Medical Center Dissertations (via ProQuest). AAI10259888.
http://digitalcommons.library.tmc.edu/dissertations/AAI10259888

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