Trump threatens to increase Canada tariffs over wildfire smoke pollution

US President Donald Trump threatened Friday a tariff increase on Canada to cover the cost of smoke pollution from wildfires that have choked large parts of the US.

Dense wildfire smoke billowing down from Canada and northern Minnesota has set off unhealthy air quality alerts across the US.

As of Saturday, there were 937 active fires in Canada, most of which were burning out of control, according to the Canadian Wildland Fire Information System.

"This is Willful Negligence, and becoming a yearly ...