Canada’s 2025 wildfire season has scorched about 7.5 million hectares—an area larger than Ireland—making it the country’s second-worst year on record. More than 700 fires were burning nationwide on 14 August, 161 of them out of control, sending repeated waves of smoke that degraded air quality across much of eastern and mid-western North America from Chicago to New York. The transboundary haze has triggered a political backlash in Washington. Republican lawmakers from several Great Lakes and Plains states filed a formal complaint with the U.S. Environmental Protection Agency and the International Joint Commission, arguing that Ottawa is not doing enough to curb the smoke and urging measures such as forest thinning and prescribed burns. They have also suggested the issue could surface in future tariff negotiations. Canadian officials counter that many fires are in remote, rugged terrain that is difficult to suppress and note that the federal government has earmarked nearly C$46 million for new research into wildfire prevention and risk assessment. Health specialists warn that the stakes extend beyond diplomacy. A study published this week in The Lancet Planetary Health found that short-term mortality linked to wildfire-generated fine particulate matter (PM2.5) may be underestimated by as much as 93 percent, with each one-microgram increase in concentration raising all-cause deaths by 0.7 percent. The findings underscore the growing public-health burden posed by Canada’s intensifying fire seasons and the smoke they send across borders.