Air quality estimates are the primary source of information regarding exposure to pollution, and their quality is important for public health, policy, and society. These estimates rely on the coverage of monitoring infrastructure across the nation.

Using September 2024 directory of active monitoring sites, we examine monitoring coverage in the United States. We find that more than half of the US counties are air quality monitoring deserts, lacking even a single monitoring station. Rural counties and those with higher indicators of social disadvantage are more likely to be air quality monitoring deserts.

The potential underrepresentation of certain areas due to limited infrastructure may result in gaps in data availability and hinder assessments of environmental or public health conditions.