US pollution measurement practices raise questions about reliability of data

Guardian analysis heightens concerns on whether the air around many large factories is, or will be, safe to breathe

A Guardian analysis has raised fresh questions over the way regulators and corporations measure the air quality impact of planned factories that risk emitting dangerous levels of pollution.

Between 2014 and 2024, air pollution permit applications in Michigan - designed to gauge if proposed industrial projects would cause regions to violate federal pollution limits - did not meet data collection rules or best practices over 90% of the time. Some measurements were taken more than a hundred miles away from sites.