Amazon.com said on Thursday that it was cutting delivery routes short for drivers in places affected by poor air quality, while Target also said its contactless order pickup service may not operate in the most affected areas.

Hundreds of forest fires are burning across much of Canada as the country sees its worst-ever start to the wildfire season, which has pushed smoke into the eastern United States, covering several cities with a thick, yellow haze. On Wednesday, New York City’s air quality was considered the worst in the world.

A spokesman for Amazon (NASDAQ:AMZN), the nation’s most valuable retailer by market capitalization, said it was cutting routes short where air quality is hazardous, and providing N-95 masks to delivery workers. Drivers were also encouraged to return to delivery stations if they felt ill.

Target Corp (NYSE:TGT) said its contactless order pick-up service called “Drive Up” may be turned off at locations with poor air quality. Customers can check their Target mobile application to confirm if the services were available at their local store, the company said.

Separately, Home Depot Inc (NYSE:HD) on Thursday said it was shipping supplies of air filters, respirator masks, box fans and air scrubbers to meet increased demand in areas dealing with poor air quality.

Schools across the region canceled outdoor activities and companies told employees to work from home, while health officials in more than a dozen states have urged millions of residents to stay indoors.