The story adds a sharper political and scientific framing: U.S. leaders are now explicitly floating tariffs or sanctions against Canada, while researchers more directly tie the worsening fires to climate change and shared responsibility. The smoke episode itself remains the same, but the policy dispute and mitigation guidance are more developed.

The story broadened from a Canada-driven smoke episode into a cross-border wildfire and air-quality crisis affecting both Canada and the northern U.S., with a stronger emphasis on heat-driven fire behavior and political blame over responsibility. It also adds a new local pollution example from Washington, D.C., to show how non-wildfire sources can worsen air-quality problems.