Impact of ozone transport mitigation policy through the NOx SIP rule on respiratory hospitalizations in New York State

Background: Few studies have examined the impacts of federal environmental policy on outdoor pollutants and health outcomes. The objective of this accountability study was to examine the health impact of the NOx State Implementation Plans (NOx SIP), a US Environmental Protection Agency mandate to reduce transport of nitrogen oxides (NOx) from neighboring states into New York State (NYS).

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

Results: Summertime ambient ozone concentrations significantly declined statewide during the post-intervention period. After adjusting for temporal trends, PM2.5, and meteorological variables, significant declines in admissions were observed following the NOx SIP in the Central (-10.2%, 95% CI:-14.2,-6.0), Lower Hudson (-11.1%, 95% CI:-16.5,-5.2), and NYC Metro regions (-5.7%, 95% CI: -7.4,-4.0), which were largely consistent with wind trajectories and likely ozone transport patterns. Stratified analyses suggest that asthma and COPD hospitalizations declined the most following intervention. Declines were observed for most age groups (-4.8 to -12.5%), and among both whites (-5.4%) and blacks (-2.7%), but not among Hispanics (7.1%). Differences in the policy impact by insurance coverage were also observed.

Conclusions: These findings provide support that positive public health impacts were associated with an environmental policy aimed to reduce outdoor ozone concentrations. The findings provide encouragement that federal mandates to reduce unintended exposure to outdoor pollutants have health benefits.