Wildfire smoke raises air pollution across US and Canada in July 2026

Brown carbon – a light‑absorbing component of soot released by wildland fires – was detected across a broad swath of the United States and Canada during a continuous seven‑day monitoring period in July 2026. Satellite observations combined with ground‑based air‑quality stations showed elevated concentrations of the pollutant, coinciding with a series of large forest fires in the western interior of North America. The surge in brown carbon contributed to a measurable decline in regional air quality, pushing the Air Quality Index (AQI) into the “unhealthy for sensitive groups” category in several metropolitan areas.

The tracking effort was coordinated by the U.S. Environmental Protection Agency, Environment Canada, and NASA’s Earth Science Division, which employed multispectral imaging and aerosol optical depth measurements to quantify the plume’s spread. Data indicated that brown carbon levels peaked at 0.8 µg m⁻³ in parts of the Pacific Northwest and the Canadian Prairies, exceeding typical summer averages by more than 150 percent. Health advisories issued by local authorities warned residents of increased respiratory irritation, especially for individuals with asthma or other pre‑existing conditions, and recommended limiting outdoor activities during the peak exposure period.

Officials emphasized that the episode underscores the growing influence of wildfire‑derived aerosols on transboundary air quality. Ongoing surveillance will continue throughout the fire season, with agencies preparing to issue further guidance should brown carbon concentrations rise again. The incident highlights the need for integrated monitoring and mitigation strategies to protect public health amid increasingly frequent and intense wildland fire events.