Millions of Americans face air quality alerts from Minnesota to New York as authorities urge people to stay indoors

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Smoke from wildfires burning in south-central Canada and parts of Minnesota is spreading across the US, prompting air quality alerts in more than 20 states with millions of Americans expected to face unhealthy air conditions this week.

The smoke from the more than 180 active wildfires in northern Ontario briefly made Toronto’s air quality among the worst in the world on Wednesday. By Wednesday night, the smoke had spread across several US states, from Minnesota, where multiple wildfires are also burning, to New York, blanketing the skies in haze and worsening air quality.

Hourly concentrations of particulate matter rose to 6.7 times their pre-fireworks levels, according to an analysis

Washington DC residents breathed in “unhealthy” air for hours after a 40-minute Independence Day fireworks show over the National Mall on Saturday night, with the country’s capital briefly recording the worst air quality of any major city in the world.

The highly emitting display, which the president called “spectacular”, came as the Trump administration rolls back an unprecedented number of pollution controls.

Babies exposed to higher levels of neurotoxin more likely to have difficulty controlling impulses later, research shows

Exposure to common air pollution may cause childhood obesity because it affects children’s ability to control impulse, new first-of-its-kind peer-reviewed research finds.

Particular matter 2.5 (PM2.5) is a neurotoxin that has been linked to obesity, and Mt Sinai researchers say they have for the first time identified impulse control as a potential pathway. The study found that babies exposed to higher levels of PM2.5 during their first year of life were more likely to develop difficulties with controlling impulses later in childhood.