The ongoing pollution "red alert" in Beijing may affect northern Japan, a model of weather patterns suggests, although pollutants will be well within safe limits when they arrive.

Noxious smog particles may drift to Hokkaido and elsewhere, according to a new simulation of air currents in the region, but residents do not need to be alarmed, the government said.

The Chinese capital this week sounded its highest ever alert over smoky haze that has engulfed the city, forcing schools to close and requiring half of all private cars to remain unused.