Associating highway density with asthma: Unraveling the link between traffic-related pollution and health in u.s. non-california metropolitan areas

This study delves into the influence of traffic-related pollution on respiratory diseases within the United States. While prior research has established a connection between air pollution and mortality or morbidity in sensitive age groups, this association has been predominantly observed in highly polluted areas, particularly in California. In this paper, we extend this line of investigation by examining adult patients with asthma symptoms across various metropolitan areas throughout the country. To address potential endogeneity concerns in our empirical framework, we adopt highway density as an instrumental variable (IV) for NO2 concentrations. This approach allows us to gain a more robust understanding of the relationship between traffic-related pollution and respiratory health outcomes. Our findings indicate that NO2 does not have a significant impact on patients with asthma symptoms in the overall sample. However, we observed that it can exacerbate asthma conditions in patients residing in warm areas. A back-of-the-envelope calculation estimates a 6.758 billion economic loss due to increasing asthma attack on adults in the selected study area. This regional disparity outside of California underscores the necessity for adjusting current regulations on vehicle emissions based on unique regional characteristics. Such adjustments could help mitigate adverse health effects associated with traffic-related pollution in different parts of the United States.