More than 100 million Americans were affected Wednesday by air quality alerts because of smoke caused by fires in Canada. These alerts cover most of the northeastern United States, from Chicago in the north to Atlanta in the south.
Cities like New York and Washington were on red alert, a level at which the general population can feel effects on their health. The populations concerned are under an "orange" alert, corresponding to a possible impact on the health of fragile people (the elderly, asthmatics, children...)