Increase in Childhood Asthma Morbidity as a Result of Climate Induced Ground-Level Ozone

An increase in respiratory illnesses has been linked to ground-level ozone pollution, which is projected to increase with climate change. Sheffıeld et al. (2011) predicted future asthma emergency department visits associated with ground level ozone changes in 2020 compared to 1990. The authors used data for emergency department visits, the relationship between ozone concentrations and visits, and projected concentrations from a well-known climate model in order to determine the relationship. A significant increase in pediatric emergency asthma visits during the summer months of 2020 was found. The effect was increased with the inclusion of population growth, but was decreased with the inclusion of ozone precursor changes.—Simone Berkovitz
Sheffield, P., Knowlton, K., Carr, J., Kinney, P,. 2011. Modeling of Regional Climate Change Effects on Ground-Level Ozone and Childhood Asthma. Am J Prev Med. 41, 251–257.

Recent research has highlighted the potential future health impacts of climate change on respiratory illnesses. Exacerbation of asthma has been linked to air pollutants, specifically ground-level ozone (O3), which is predicted to increase with climate change. O3 is not directly emitted into the air, but is formed through a reaction between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight. Ground-level ozone is known as a summertime pollutant and significantly increases with temperature. Several studies have modeled global mortality and morbidity of asthma due to climate change, however regional projections for pediatric asthma have not been explored. Therefore, Sheffıeld et al. aimed to predict the effects of climate-driven, ozone related pediatric asthma in the New York Metropolitan area. 
            This study used a health impact assessment to look at O3-related asthma emergency department visits for children aged 0–17 in the 2020s compared to the 1990s. A 36 x 36 km grid of the New York City Metropolitan area, which included 14 counties, was used to conduct the study. By linking models for global climate, regional climate, and regional air quality, the authors were able to develop projections for ground-level O3. Greenhouse gas emission future predictions were based upon the IPCC A2 scenario, which assumes relatively rapid emissions and population growth.  Due to computational constraints, the study only modeled outputs for June-August. A morbidity analysis was performed in order to determine the mean number of daily asthma emergency department visits due to daily 8-hour maximum O3 concentrations. This was calculated using population, the county-level daily asthma emergency department visits rate, and the ERC, which is the exposure-risk for asthma morbidity due to a change in O3. First, the effects of climate change on summer O3 concentrations were looked at in order to project asthma emergency department visits, then two sensitivity analyses were conducted to incorporate the effects of population growth and other pollutants.
            Sheffıeld et al. found that in all of the fourteen counties, an increase in O3 would result in a greater number of asthma emergency department visits in both surrounding metropolitan counties and the central urban areas.  The results suggest that climate change could cause a 7.3% regional summer increase in asthma emergency department visits in children aged 0–17, however the percentage increase varied across individual counties. The sensitivity analysis demonstrated that as population is predicted to increase in urban areas, a higher percent increase in morbidity was found. The second analysis found a decrease in visits when the effects of climate change were isolated, due to the influence of other pollutants, which can mix to decrease O3 levels.
            An increase in pollution and temperature will have serious adverse effects on respiratory illnesses. The authors realized that their study had several limitations such as the assumption of uniform exposure to ozone across all the counties and the application of a single ERC. It is clear this model simplifies the complex relationship between climate change, O3 prevalence, population growth, and asthma prevalence, but it is important to realize the effects of climate change on disease in children. This study provides an important modeling approach, but the quantitative future predictions should be interpreted loosely. 

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