A heat wave on the East Coast could break records — and it's prompting warnings about dangerously poor air quality

  • A heat wave is making its way across the US, bringing potentially record-breaking temperatures to the Midwest and Northeast.

  • Air-quality alerts were issued in New York, Pennsylvania, and southern New England.

  • In hot weather, emissions from vehicles and power plants can react to form ozone, which can cause respiratory problems for children, elderly people, and those with pre-existing illnesses.

A record-breaking heat wave is sizzling across the US, bringing scalding temperatures and dangerous air pollution.

Chicago experienced its hottest Father's Day since 1995 on Sunday, with the thermometer at Midway Airport hitting 103 degrees Fahrenheit, according to the National Weather Service. The city is still under an excessive heat warning as of Monday morning.

That hot air has made its way east, where it's blanketing the Northeast, including Washington, DC, Pittsburgh, and New York City.

Temperatures may hit 95 degrees in New York this afternoon, which would be equal to the record-high temperature set in 1929, according to AccuWeather. Boston, Connecticut, and other parts of southern New England may also see temperatures in the high 90s. The National Weather Service issued a heat advisory for the greater Boston area, parts of New Hampshire, Connecticut, and southern Maine. A few schools in the Camden school district in Pennsylvania closed Monday morning due to the heat.

The New York State Department of Environmental Conservation issued an Air Quality Health Advisory for New York City, Long Island, and much of the Hudson Valley in response to the rising temperatures on Monday, urging people to limit outdoor exercise and curb the use of emissions-spewing vehicles and appliances. The advisory is in effect from 11 a.m. to 11 p.m.

Pennsylvania's Department of Environmental Protection also issued a Code Orange air-quality alert for Pittsburgh and Philadelphia, which means that young children, the elderly, and people with respiratory problems are vulnerable to health issues from air pollution.

Why heat waves cause air quality to plummet

The main air-quality concern is the formation of ground-level ozone, which can be especially dangerous to children, the elderly, and people with respiratory illnesses like asthma.

Ozone in the upper atmosphere forms naturally and is useful for protecting Earth against the sun's harmful UV rays. But when the gas is created by human activity closer to the ground, it can cause severe problems.

Ground-level ozone forms when certain types of pollutants are emitted from cars, power plants, and refineries that burn gasoline or coal. The sun's heat spurs those compounds to react with naturally occurring gases, creating what's known as tropospheric ozone. The rate at which this ozone is produced increases with temperature, so the hotter it is, the more ozone pollution there will be.

That process, combined with the lack of wind on hot days, is why smog tends to hangs around on summer days. Ozone levels are usually highest in the early evening, since the amount of emissions in the air rises throughout the day. They then decrease at night as the temperature drops.

"People, especially young children, those who exercise outdoors, those involved in vigorous outdoor work, and those who have respiratory disease (such as asthma) should consider limiting strenuous outdoor physical activity when ozone levels are the highest (generally afternoon to early evening)," New York's Department of Environmental Conservation (DEC) said in its advisory.

The warning added: "When outdoor levels of ozone are elevated, going indoors will usually reduce your exposure. Individuals experiencing symptoms such as shortness of breath, chest pain, or coughing should consider consulting their doctor."

To help reduce ozone pollution, the DEC recommends carpooling or taking public transit, shutting your lights off, limiting the use of appliances in your home or office, and refraining from outdoor burning like grilling or smoking cigarettes.

Heat waves and air pollution are likely to get worse

Heat waves and record-breaking temperatures are becoming more common around the world due to climate change, and are expected to get worse. By 2075, strong heat waves that currently occur once every 20 years could become annual events on 60% of the Earth's land areas. Swaths of Pakistan, Bangladesh, and northern India could become uninhabitable over the next few decades because of extreme heat.

That will cause the air pollution problems in cities to get worse as well.

According to a Harvard study, climate change could contribute to an additional three to nine days per year of unhealthy ozone levels — amounting to a 70-100% increase in ozone days, depending on the region.

California, the Southwest, and the Northeast will be among the most affected areas, seeing up to nine additional ozone days per year, according to the study.

The air-quality warnings of today could therefore be just a preview of what's to come if emissions continue unchecked.

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