Trump threatens Canada with steeper tariff costs over wildfire smoke

US President Donald Trump has threatened to impose additional tariffs on Canada as a penalty for the wildfire smoke that has clouded cities across North America. Trump blamed Canadian governance for the fires, claiming the US was 'invaded by filthy, polluted, and unhealthy air'. He pledged to call Prime Minister Mark Carney and add the costs to existing tariffs. Scientists attribute the proliferation of wildfires to climate change.