Impact of Ozone Transport Mitigation Policy through the NOx SIP Call on Children's Respiratory Hospitalizations in New York State

BACKGROUND: Limited studies have examined the impacts of federal environmental policy on outdoor pollutants and health outcomes. The objective of this study, was to examine the health impact on children of the NOx SIP call, a US Environmental Protection Agency rule that required Northeast states and the District of Columbia to submit state implementation plans (SIPs) that address the regional transport of ozone, through reductions in nitrogen oxides (NOx) emissions, implemented fully in 2003.   

METHODS: A time-series analysis was used to assess the health impacts of the implementation of the NOx SIP call in NYS. Outdoor ozone concentrations and child respiratory hospitalizations were compared between baseline (1997-2000), partial-implementation (2001-2003) and post-implementation (2004-2006) periods, adjusting for temporal trends and meteorological factors. 

RESULTS: Summertime ambient ozone concentrations statewide significantly declined during the post-intervention period. After adjusting for temporal trends, particulate matter (PM_2.5), and meteorological variables, significant declines in child respiratory admissions were observed following the implementation of the NOx SIP call in the Long Island (-11.1%,  95% CI: -20.0,-1.3), NYC Metro (-21.7%, 95% CI: -24.5,-18.7), Upper Hudson (-21.3%, 95% CI:-34.2,-5.8) Eastern Ontario (-23.1%, 95% CI: -36.3, -7,2) and Central(-35.3%, 95% CI:-44.3,-24.9) regions.  Stratified analyses suggest that respiratory hospitalizations, among children; 5-17 years old, White and Others race, parental insurance classified as self-payers, Medicaid-covered, declined the most post-full NOx implementation period.

CONCLUSIONS: This research found that positive public health impacts on children were associated with an environmental policy aimed to reduce outdoor ozone concentrations.The findings demonstrated encouragement that federal mandates to reduce exposure to outdoor pollutants have health benefits. However, the effect varied by region and socio-demographic characteristics.