Pacific Northwest Wildfires

Altering Air Pollution Patterns across North America

Increasingly large and intense wildfires in the Pacific Northwest are altering the seasonal pattern of air pollution and causing a spike in unhealthy pollutants in August, new research finds. The smoke is undermining clean air gains, posing potential risks to the health of millions of people, according to the study.

The research, led by scientists at the National Center for Atmospheric Research (NCAR), found that levels of carbon monoxide—a gas that indicates the presence of other air pollutants—have increased sharply as wildfires spread in August. Carbon monoxide levels are normally lower in the summer because of chemical reactions in the atmosphere related to changes in sunlight, and the finding that their levels have jumped indicates the extent of the smoke’s impacts. “Wildfire emissions have increased so substantially that they’re changing the annual pattern of air quality across North America,” said NCAR scientist Rebecca Buchholz, the lead author. “It is quite clear that there is a new peak of air pollution in the month of August that didn’t used to exist.”

Although carbon monoxide generally is not a significant health concern outdoors, the gas indicates the presence of more harmful pollutants, including aerosols (airborne particulates) and ground-level ozone that tends to form on hot summer days.

The research team used satellite-based observations of atmospheric chemistry and global inventories of fires to track wildfire emissions during most of the past two decades, as well as computer modelling to analyse the potential impacts of the smoke. They focused on three North American regions: the Pacific Northwest, the central United States, and the Northeast.