The Brief

The smog appeared out of nowhere on July 8, 1943, blinding drivers and causing car crashes. Mothers grabbed their children and ran inside hotels to escape unwanted fumes. Some thought it was chemical warfare by a foreign country. But no, it was smog.

Former Los Angeles Mayor Fletcher Bowron said he would get rid of the "vexing fumes" within four months. The problem persisted for more than four decades.

L.A. has made progress on the stuffy air, which was once so thick it burned lungs and eyes and caused nausea. But the fight for clean air is far from over as Los Angeles still remains one of the worst-air-polluted cities in the country.

What brought the smog?

People initially blamed the smog on a gas company plant that made artificial rubber. Then, they blamed sulfur.

Chip Jacobs is a co-author of Smogtown: The Lung-Burning History of Pollution in Los Angeles. He said it was almost like L.A. was in a state of denial.

"Some people started suspecting it's cars, it's hydrocarbons from cars reacting in sunlight," he said in an interview with LAist's daily news program AirTalk, which airs on 89.3 FM. "That was not appreciated and embraced until a little scientist at Caltech took a chance."

That scientist was Arie Haagen-Smit, who escaped Holland to avoid World War II. According to Jacobs, he didn't want to be a scientist. But he was angry at the weak science around investigating smog. Lab work revealed tailpipe emissions were the smog culprit. Still, not a lot of people wanted to believe him.

"He was going up against the coolest product you could buy, a car," Jacobs said.

Feeling the burn

The smog ruined the great outdoors for many people in the decades to follow. AirTalk caller Joanne grew up in L.A. during the 1950s. She told host Larry Mantle that when she came home from college she asked her mom, "How can you live here?"

"It felt like the entire world was peeling onions," she said. "That's the only way I can describe it."

Other callers chimed in and remembered schools closing in the 1960s because the air pollution was so bad.

Mantle remembered burning lungs as a child.

"I just remember my lungs burning and wondering, wow, why is that? What's causing this?" Mantle said. "You don't really know what's going on because you take the smog for granted."

Jacobs also said it ruined a lot of fun for him in the 70s. He recalled canceled baseball games.

"You start with a blue sky, and it seemed like a fog rolled in. All of a sudden your asthmatic friends were running for the primatene mist," Jacobs said.

What changed? 

Ed Avol is a professor emeritus at the Keck School of Medicine at USC in the population and public health science department. He said cleaning up the air has been a huge success story in understanding improvement in Los Angeles.

He pointed to technology and policies through the state and regional agencies on refineries, power plants, and chemical and manufacturing.

Avol also credited regulations on trains, planes, ships and cars. Those included smog checks for cars, lead removal from gasoline, and catalytic converters that helped clear some of the air.

"The problem is really so vast here, and so many millions of sources here, that really one has to do a sort of full court approach to try and address everything we can to try and reduce that,” Avol said.

Listen to the conversation

Four million acres of California’s wildest backcountry could soon be opened to paving roads and logging.

The Trump administration announced last week that it’s pushing forward with a proposal to scrap a 2001 rule that blocks logging, road building and other construction in parts of national forests. The administration argues repealing the so-called “roadless rule” is key to managing vegetation to better prevent wildfires on public lands.

Environmental advocates and other groups worry rescinding the rule would harm pristine habitat and the wildlife it supports, and open up more public land to industrial activities and human access that can cause more wildfires.

And locals are worried about losing access to some of the last protected natural lands in the region.

“What we're dealing with here in the roadless rule is the protection of the backcountry,” said David Browning, president of the Orange County Mountain Bike Association, “where you can actually go out and be having an experience where you don't hear traffic, where you don't see buildings, where you actually remember what it was like before all of us got here.”

In Southern California, large swaths of the Los Padres, Angeles, San Bernardino and Cleveland national forests would lose protections.

Browning, who spoke with All Things Considered host Julia Paskin on Monday, said he’s particularly concerned about the Santa Ana Mountains, where much of Orange County’s backcountry biking trails exist within a roadless area that could be opened to construction.

“Our mission is to protect and expand trail access, and so our entire agenda is to make sure that in a highly populated county, like Orange, that we have available the outdoors to be able to go and enjoy,” he said.

Browning takes issue with the wildfire argument — he pointed to the 2024 Airport Fire, which was sparked when heavy equipment operated by Orange County employees struck a rock. They were moving large boulders that day to, in part, block vehicles from getting into a dry brush area and potentially starting a fire. Browning said the “roadless rule” prevents such access that could increase the risk of fire. A recent peer-reviewed study supports that, finding that although roads are important for managing a fire once it ignites, they’re also more likely to be a place where a fire starts.

Though addressing wildfires and protecting public lands have become heavily politicized under the Trump administration, Browning thinks most locals probably aren’t as divided.

“ I don't think this is a party issue,” he said. “We want to hold onto the outdoors and protect them as best we can.”

There unfortunately isn’t much respite in sight for heat-weary Southern Californians.

Forecasters say this week’s heat wave is likely to be the hottest so far this summer. Extreme heat warnings will be in effect from the National Weather Service for almost the entire region from Tuesday morning through Friday evening.

Temperatures will peak between Tuesday and Thursday.

Highs in downtown Los Angeles are expected to reach around 100 degrees, and the warmest inland valleys will get up to 112. L.A. County beaches will hit the high 80s.

Forecasters have also issued Red Flag Warnings for the interior mountains and foothills of Los Angeles, Ventura and Santa Barbara counties. Gusty winds and low humidity at higher elevations mean fires could spark and spread quickly.

At lower elevations, humidity continues to make the heat feel more sweltering and make it harder to cool down, especially at night. Nighttime temperatures will only get down to the 70s in most places, including along the coast.

A slight cooldown is expected this weekend, though forecasters say temperatures will stay above normal into next week.

The extreme heat this week poses an especially high risk of heat-related illness for people over 65, young children, people who work or spend a lot of time outside and those without access to air conditioning.

Driving the heat

Several factors are behind this week’s heat wave, many of which have also been behind the rest of this summer’s consistently hot weather.

The main driver is a high pressure air system hovering over the southwestern U.S., trapping warm air, compressing it and warming it further, and blocking cooler air from entering the region.

Offshore winds are also pushing warm inland air toward the coast, preventing cooler onshore winds from blowing inland.

“That blocks our natural air conditioning off the ocean from coming in as early as it normally does,” said Weather Service meteorologist Mike Wofford. “So as long as that cool air stays offshore, it heats up on land.”

The offshore winds are not strong enough, however, to significantly dry out the air in the L.A. Basin and cut down on the humidity.

“That's probably going to be around for the whole summer because you’ve got all this warm ocean water that's feeding into that,” Wofford said.

Warmer seawater evaporates faster, adding to moisture in the air and increasing humidity across the region, especially along the coasts.

Air quality warnings

Along with the heat this week, many Southern Californians also have smog to worry about.

The South Coast Air Quality Management District issued an ozone advisory on Monday for inland areas of Los Angeles and Orange counties, much of Riverside County and parts of San Bernardino County. It will remain in effect through Friday evening.

The multi-day smog event is in part driven by the heatwave.

Officials say ozone pollution may reach unhealthy levels or higher in the Santa Clarita Valley, parts of the San Gabriel and San Bernardino valleys, and portions of the San Bernardino Mountains.

Under unhealthy levels, it’s possible for anyone to experience adverse health effects like difficulty breathing and throat irritation. Sensitive populations could experience more serious effects.

Levels are expected to be unhealthy for sensitive groups in the San Fernando Valley, Perris Valley, Mission Viejo, Lake Elsinore, Corona, Hemet, Riverside and Pasadena.

Officials advise certain vulnerable groups — including people with heart or lung disease, those with asthma, pregnant women, children and people over 65 — to limit their time outdoors.

Officials predict that ozone levels will be lower along the coast.