Environmental injustice and inequality: NO2 air pollution in the United States

Abstract

Background: Communities with lower socioeconomic status often have higher exposure to air pollution and higher susceptibility to air pollution health impacts. Aim: To describe and compare environmental injustice and inequality in residential outdoor air pollution for the entire contiguous United States population, including both urban and rural areas. Methods: We employ a recent national land-use regression for Census block –level nitrogen dioxide (NO2) and Census socioeconomic data (~1-km2 urban spatial resolution). Our analyses compare population-weighted NO2 concentrations by socioeconomic characteristics (race-ethnicity, income, poverty status, education level) and calculate environmental injustice and inequality statistics for US regions, states, counties and urban areas. Results: Nationally, population-weighted mean NO2 concentrations are 3.4 ppb (27%) higher for low-income nonwhites than high-income whites. Inequality for NO2 concentration is greater than inequality for income (Atkinson Index: 0.11 [NO2] versus 0.08 [income]). NO2 disparities are similar in magnitude by income and by race. For example, within individual urban areas, NO2 concentrations are, on average, ~8% higher for nonwhites than whites (after controlling for income) and ~5% higher for low-income than for high-income groups (after controlling for race). Ambient NO2 concentrations are higher than average for low-income nonwhite young and old people. Conclusions: Previous work has documented air pollution environmental injustice and inequality within individual US metropolitan areas and regions; our research establishes a national context for trends throughout the continental US.