US environmental regulators change how they measure air pollution in some areas

US environmental regulators are changing how they designate areas for air quality planning. This means some regions will now be measured against different pollution standards than before.

For decades, the US has used specific air quality standards to decide which areas need to clean up their air. This rule changes the technical details of how those areas are identified and categorized. It means some places might face new requirements, while others might see existing ones eased, all based on how their air pollution is now measured.