Investigating short-term effects of PM2.5 components on mortality and morbidity in Greater Houston, Texas
Exposures to ambient PM2.5 (particulate matter with an aerodynamic diameter of ≤ 2.5 μm) have been associated with a variety of adverse health effects, including respiratory symptoms, aggravated asthma, cardiovascular disease, lung cancer, and increased mortality. Compared to the health effects of PM2.5 mass that have been extensively studied, fewer studies have focused on health effects of PM2.5 components. In this dissertation, we conducted three time-series studies to investigate short-term associations between PM2.5 components and three health outcomes: mortality, emergency department visits, and emergency hospital admissions in Greater Houston, Texas. For emergency department visits and hospital admissions, we focused on a privately insured company (Blue Cross and Blue Shield of Texas [BCBSTX]) rather than the general public or national social insurance programs such as Medicare or Medicaid. Because BCBSTX covers mostly the working aged individuals, studying such a population adds to the literature linking exposure to PM2.5 components and adverse health effects of a population that is closely related to economic development.^ In the first study, we found that PM2.5 mass concentrations were statistically significantly associated with increased mortality risk during 2000 - 2011. This association decreased over time when effect estimates of PM2.5 mass between 2000 - 2005 and 2006 - 2011 were compared. Among selected PM2.5 components, ammonium, nitrate, sulfate, and vanadium were statistically significantly associated with an increased risk in mortality of Seasonal analysis suggested that the associations were strongest during the winter months. In the second study, we found that bromine, potassium, sodium ion, and sulfate were statistically significantly associated with an increased risk in total ED visits. In addition, bromine and nickel were statistically associated with increased ED visits for stroke. Aluminum, chromium, and potassium were significantly associated with increased ED visits for respiratory problems. Seasonal analysis suggested that effect estimates for most PM2.5 components were higher during the warm season. In the third study, we found that arsenic and copper were associated with increased emergency hospital admissions for stroke and pneumonia.^ Our results show that the short-term associations between PM2.5 and mortality differ across the PM2.5 components; this suggests that future air pollution control measures should not only focus on mass but also components, especially those with high toxicities. Our results on emergency department visits and hospital admissions indicate that, although presumably healthier than the general population, the privately insured population may be still at risk of adverse health effects due to exposure to ambient PM 2.5 components.^
Liu, Suyang, "Investigating short-term effects of PM2.5 components on mortality and morbidity in Greater Houston, Texas" (2016). Texas Medical Center Dissertations (via ProQuest). AAI10182184.