Hospital admissions for asthma and acute bronchitis in El Paso, Texas: do age, sex, and insurance status modify the effects of dust and low wind events?

BACKGROUND: El Paso County (Texas) is prone to still air inversions and is one of the dust "hot spots" in North America. In this context, we examined the sub-lethal effects of airborne dust and low wind events on human respiratory health (i.e., asthma and acute bronchitis) between 2000 and 2003, when 110 dust and 157 low wind events occurred. Because environmental conditions may not affect everyone the same, we explored the effects of dust and low wind within three age groups (children, adults, and the elderly), testing for effect modifications by sex and insurance status, while controlling for weather and air pollutants. METHODS: We used a case-crossover design using events matched with referent days on the same day-of-the-week, month, and year with conditional logistic regression to estimate the probability of hospital admission, while controlling for apparent temperature (lag 1), nitrogen dioxide, and particulate matter of 2.5µm or less. RESULTS: Children (aged 1-17) were 1.19 (95% confidence interval: 1.00-1.41) times more likely to be hospitalized for asthma three days after a low wind event, and 1.33 (95% CI: 1.01-1.75) times more likely to be hospitalized for acute bronchitis one day after a dust event than on a clear day. Girls were more sensitive to acute bronchitis hospitalizations after dust events (1.83, 95% CI: 1.09-3.08) than boys, but less sensitive than boys to acute bronchitis hospitalizations after low wind events (0.68, 95% CI: 0.46-1.00). We found general trends with regard to dust and low wind events being associated with increased odds of hospitalization for asthma and bronchitis amongst all ages and adults (aged 18-64). Adults covered by Medicaid and adults without health insurance had higher risks of hospitalization for asthma and acute bronchitis after both low wind and dust events. CONCLUSIONS: Results suggest that there were respiratory health effects associated with dust and low wind events in El Paso, with stronger impacts among children and poor adults. Girls and boys with acute bronchitis were differentially sensitive to dust and low wind events.

Children's asthma hospitalizations and relative risk due to nitrogen dioxide (NO2): effect modification by race, ethnicity, and insurance status.

BACKGROUND: This study explores the role of race, ethnicity, and insurance status in modifying the effects of air pollution on children's asthma hospitalizations in Phoenix, Arizona (US) between 2001 and 2003. While controlling for weather, interactions between nitrous dioxide (NO(2)) and race, ethnicity, and insurance status are used to predict relative risk for subgroups of children. METHODS: The generalized logit regression model for nominal categorical data within a multinomial likelihood framework was used. This model is specifically suited to small counts and the reporting of 95% confidence intervals for the odds ratio of hospital admission for one group as compared to another. The odds ratio is known to approximate relative risk for rare events. RESULTS: Several significant findings were found for race, ethnicity, and insurance status as modulators for the effect of NO(2) on children's risk for asthma hospitalization: (1) children without insurance have 1.4 (95% CI: 1.1-1.8) times higher risk of asthma admissions than those with private insurance at exceedances of 0.02 parts per million (ppm) of NO(2) above the seasonal mean; the same finding holds for children without insurance as compared to those with Medicaid; (2) black children have 2.1 (95% CI: 1.3-3.3) times higher risk of hospitalization than Hispanic children at seasonal mean NO(2) levels, but this disproportionate risk shrinks to 1.7 with exceedances of 0.02 ppm of NO(2) above the seasonal mean. Specific to finding (1) among those children without health insurance, Hispanic children have 2.1 (95% CI: 1.1-3.8) times higher risk of hospitalization than white children. Among all Hispanic children, those without health insurance have 1.9 (95% CI: 1.3-3.0) times greater risk than those with private insurance; the same finding holds for Hispanic children without insurance as compared to Hispanic children with Medicaid. Specific to finding (2), among children with private insurance, the disproportionate risk of black children as compared to Hispanic children is magnified by a factor of 1.3 (95% CI: 1.0-1.8) for exceedances of 0.02 ppm of NO(2) above the seasonal mean. CONCLUSIONS: Although we cannot confirm a cause-effect relationship, this analysis suggests that increasing insurance enrollment for all children, and specifically Hispanic children, may reduce their disproportionate risk from exceedances of air pollution. There are few black children in Phoenix, so further studies are needed to investigate the increasing risk of black children with private insurance as compared to Hispanics at exceedances of NO(2).