Air pollution contributes to the global burden of disease, with ambient exposure to fine particulate matter of diameters smaller than 2.5 μm (PM_2.5) being identified as the fifth-ranking risk factor for mortality globally. Racial/ethnic minorities and lower-income groups in the USA are at a higher risk of death from exposure to PM_2.5 than are other population/income groups^{, , –}. Moreover, disparities in exposure to air pollution among population and income groups are known to exist^{, , , , , , , , , , –}. Here we develop a data platform that links demographic data (from the US Census Bureau and American Community Survey) and PM_2.5 data across the USA. We analyse the data at the tabulation area level of US zip codes (N is approximately 32,000) between 2000 and 2016. We show that areas with higher-than-average white and Native American populations have been consistently exposed to average PM_2.5 levels that are lower than areas with higher-than-average Black, Asian and Hispanic or Latino populations. Moreover, areas with low-income populations have been consistently exposed to higher average PM_2.5 levels than areas with high-income groups for the years 2004–2016. Furthermore, disparities in exposure relative to safety standards set by the US Environmental Protection Agency and the World Health Organization have been increasing over time. Our findings suggest that more-targeted PM_2.5 reductions are necessary to provide all people with a similar degree of protection from environmental hazards. Our study is observational and cannot provide insight into the drivers of the identified disparities.