In a state known for tough clean-air regulations, the drought has unleashed unprecedented levels of dust and smoke in the air.

The policies that made California a model of how big, developed economies can thrive while safeguarding the environment did not originate in some statewide sense of kumbaya.

They were a desperate response to serious air quality problems in Los Angeles, Bakersfield, and Fresno.

Bad air is a serious drag on public health, driving up rates of cardiovascular disease, cancer, asthma, and death.

California’s efforts to rein in pollution — by requiring smog tests for all cars and trucks and mandating that utilities generate a significant fraction of the power they sell from renewable sources — have delivered decades of improvements in ozone and particulate matter pollution.

But the severe drought the state has weathered the past three years threatens to roll back those gains.

“Air quality was improving and [the San Joaquin air districts] were making good progress toward attaining the federal standard,” said Sylvia Vanderspek, chief of the air quality planning branch of the California Air Resources Board (CARB). “And then the drought happened.”

The San Joaquin Valley, a poor agricultural region that has long been a trouble spot for pollution, has experienced air quality so bad this year that public health officials warned residents to stay inside unless they had no other choice.

The same stagnant air that has, with ruthless efficiency, kept the rain out of California has kept the pollution in.

The San Joaquin Valley, the part of the Central Valley that runs from Sacramento to Bakersfield, is especially vulnerable. Southern winds bring pollution, as do vehicles that produce it along two major highways that run down the valley.

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In the winter, with no rain to speak of, residents of the San Joaquin Valley faced “abnormally high” levels of fine particle pollution. Levels even dwarfed past years when the area didn’t meet federal air quality standards.

If officials hadn’t set stricter standards for the use of fireplaces and wood stoves, offering to reimburse poor residents who upgraded to clean-burning alternatives, conditions would have been worse.

“Pollution just builds up day after day. The only time the numbers go down is if we’d have a windy day or something,” said Vanderspek.

It’s clear that the drought has ramped up pollution that had otherwise been waning. And even before it did, fine particle pollution — a mix of ammonium nitrate, ammonium sulfate from industrial and vehicle emissions, along with burned wood and geologic material — killed about 9,000 Californians a year as of 2010.

Then there’s larger particulate matter, made up almost entirely of dust. Farmers have been forced to stop watering more than 500,000 acres of farmland statewide, the vast majority of it in the Central Valley. Those empty fields are turning to dust, which residents breathe in.

Large particulate pollution in the San Joaquin Valley hit a low point in 2010 and has been rising since then.

The dust comes with an additional cost. The lion’s share of jobs in the San Joaquin Valley are agricultural. Crops were limited because of water shortages, leading agribusiness to cut its headcount by 5 percent in 2014 and again in 2015.

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The summer brought still more dramatic challenges.

The drought has turned the wooded mountains that surround the San Joaquin Valley’s farmland into kindling. The 2015 wildfire season was the most destructive on record, with fires so big and fast-moving that they’ve been dubbed “super fires.”

As the fires blazed along the western edge of the Sierra Nevada, smoke and ash poured downwind into the valley. Fresno saw what Bonnie Holmes-Gen, senior director for air quality and climate change for the American Lung Association, called “nightmare scenarios.”

“There was just like ash floating in the air. It was bad,” she said.

Anyone, however hale and hearty, who has been enveloped in the smoke and haze that billows out from wildfire knows it’s unpleasant.

But until 2008, environmental regulators weren’t sure that this natural smoke posed a real threat to public health. That year was the last time, before 2015, when an exceptional amount of the state’s acreage burned. It was also the year Colleen Reid was an intern at a California branch of the Environmental Protection Agency (EPA).

The office was fielding a steady stream of calls from concerned citizens breathing in smoke and wondering if it was bad for them. The staff, accustomed to thinking of air pollution as the emissions from cars and factories, couldn’t quite wrap their heads around it. So they let the intern dive into it. Reid went on to get a Ph.D. studying the effects of wildfire on air quality and health.

The findings have been pretty grim, given that climate models predict that both drought and wildfire will become the new normal in California. Wildfire season in the state has gone from five months to nearly year-round as the area at risk has expanded.

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Reid’s research has shown that smoky conditions drive up the number of patients with chronic obstructive pulmonary disease and respiratory infections seeking medical attention. She’s shown that birth weights are lower for babies who were in the womb while a nearby fire blazed.

Other researchers have found that there are more heart attacks and more deaths on days when smoke hangs in the air.

The strongest connection is to emergency room visits for those with asthma, Reid said. This summer, Fresno public health officials reported a four-fold increase in the number of people seeking medical care for asthma.

The science on how wildfire smoke affects us is still in its earliest stages. However, the direction it’s headed seems pretty clear. Wood smoke is 12 times more carcinogenic than an equal concentration of cigarette smoke.

The impacts are serious enough that residents in the San Joaquin Valley, one of the poorest regions in the state, saw public health warnings like this one over the summer: “Smoke levels are in the unhealthy range today and expected to remain there for several days. Everyone should remain indoors as much as possible.”

In a state that’s made enormous strides to reduce the toll that bad air takes on its residents, it seemed like a somber step backward.

But the methods that have served the Golden State so well in decades of pushing industry to provide cleaner trucks, cars, boats, and fireplaces don’t translate easily when it comes to dealing with wildfires.

California is “leading the nation in our response to the manmade emissions that are driving global climate change,” said Juliet Christian-Smith, Ph.D., a climate scientist at the Union of Concerned Scientists.

But the state is struggling to deal with the effects of climate change that are already locked in, she said.

“That’s just a very difficult job because we don’t have an institutional framework set up to deal with interdisciplinary problems like drought contributing to increased wildfires,” Christian-Smith said.

Vanderspek put it this way: “Wildfires are a significant problem when you’re dealing with air quality, but I think from a planning perspective, it’s not something that we can control.”

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But is there really nothing the state can do to blunt the poisonous effects smoke has on its citizens, beyond telling them to stay inside with an air conditioner, which many can’t afford?

Max Moritz, Ph.D., a professor of environmental science at the University of California at Berkeley, sees room for improvement.

“We have earthquake kits,” he said, “but we don’t have wildfire kits.” There are some $30 masks that could help protect people’s lungs, for example.

Government can’t control where fires happen, but it could do more to ensure that fires are smaller when they do occur. That means controlled burns, which the state’s Department of Forestry and Fire Management, known as Cal Fire, advocates.

But, ironically, the state’s air quality restrictions make controlled burns difficult to accomplish, Moritz said.

Cal Fire can only conduct controlled burns under certain conditions. Moisture and wind conditions have to be favorable, so the burns don’t blaze out of control. And air quality has to be good or the state will put the kibosh on burn plans.

“Air quality restrictions are pretty stringent now and it’s pretty rare that prescribed burns can be used,” Moritz said.

In other words, to protect air quality in the short term, one agency forbids the action that another has identified as the best way to limit wildfire smoke in the long run.

“Maybe it’s because we’re in the early stages of coexisting with wildfire, but we’re still operating under some guidelines and perspectives that are built on the recent past. A lot of them are just not going to work,” he said. “We’re going to have to think outside the box.”

But air pollution isn’t the only, or even the worst, problem California faces as the result of its historic drought. It’s also going to have to get by with less water for more people, even if the state does get the wet winter climatologists predict.

Part II of this series will explore the effects of the drought on water quality, as well as expected public health effects of the anticipated El Nino weather phenomenon.