Julio Cortez/AP

A lesson in an essential element of summer.

With a mid-week holiday in the U.S., we’ve all got summer on our minds. So we’re trying something a little different for the CityLab Daily this week, exploring the essential elements of summer in the city. Find our latest stories at the end, and as always, let us know what you think at hello@citylab.com.

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Catch a great fireworks show last night? If so, you might’ve noticed something else in the sky this morning. The smoke after Fourth of July fireworks produces a spike in air pollution that you can actually see and breathe. Using data from 2017, CityLab’s David Montgomery visualized just how much particulate matter gets blasted into the air on America’s birthday. That big spike comes around 10 p.m. local time in places across the country and tapers off throughout the next day. The particulate matter levels are roughly equivalent to the difference in air quality between Los Angeles and Beijing.

A chart shows air pollution spikes during July 4 fireworks.

In a way, it underscores just how good the U.S. has it; it’s worth remembering how recently it became possible to enjoy summer en plein air in the city. Photos show how much of a barrier pollution posed to urban life before the EPA stepped in, and still today we’re learning more about the health consequences of poor air quality: A new research paper finds a link between air pollution and diabetes.

Some other cities are still experiencing extreme pollution all year round. Undergoing massive population and economic growth, cities like Delhi and Seoul have experimented with car bans and free public transit to curb the problems of pollution and smog. And even in the U.S. there are still ZIP codes where it’s hard to breathe. So when the smoke clears out today, take a deep breath to appreciate the progress cities have made so far, and the work that’s still to be done.

From the CityLab archives:

Andrew Small

Summer Icon: The Air Conditioner

A photo shows a window air conditioning unit.
(David Mercer/AP)

The modern air conditioner, invented in 1902 by Willis Carrier in Buffalo, New York, provided the first affordable way to keep cool indoors—but it took a while to catch on. Air conditioning spread to department stores, rail cars, and offices in the 1930s, but by 1965, only 10 percent of U.S. homes had an A/C unit, as Will Oremus notes in Slate. Before the air conditioner, city dwellers had to go to great lengths to stay cool, even sleeping on fire escapes, porches, and roofs when it got too hot.

Today, of course, the air conditioner is ubiquitous, with about an 87 percent adoption rate in U.S homes. It has shaped how architects design buildings and where cities can even exist, perhaps most famously making the Sun Belt much more inhabitable. But America’s love for the air conditioner isn’t exactly sustainable. If the rest of the world used A/C like the U.S., there would be about 45 times as much energy usage devoted to cooling homes—though research has suggested that heating actually uses way more energy than keeping cool.

By the Numbers

5.5 million: Estimated number of premature deaths caused each year by air pollution

133.9 million: Population of Americans who live in a county exposed to unhealthful levels of ozone or particle pollutants

170 million: Equivalent number of cars on the road to create the 1.7 percent increase in global carbon emissions from 2016 to 2017

26 percent: How much the U.S. promised to reduce carbon emissions from 2005 levels by 2025, before backing out of the Paris Climate Accord

24: Pounds of carbon dioxide and other global-warming gas emitted for every gallon of gas consumed

6.511 billion: Metric tons of carbon dioxide emitted by the U.S. in 2016

???: The number of air-conditioning units that fall from windows and hit people in New York (but it’s almost zero)

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