Higher Air Pollution Is Linked To A Higher COVID-19 Death Rate, A New Study Finds

Long-term exposure to high levels of air pollution increases the risk of death related to COVID-19, according to a new study from Harvard University.

That’s especially concerning in Southern California, where Los Angeles, Riverside and San Bernardino counties regularly rank among the worst in the nation for long-term particulate matter pollution, or PM2.5.

And, as is true in other parts of the nation, the effects of that pollution disproportionately harm Latinos, African Americans, Asian Americans and low-income communities — which underscores early data showing black Americans are dying at higher rates from COVID-19 complications.

The Harvard study gathered data from roughly 3,000 U.S. counties, which account for 90% of confirmed COVID-19 deaths nationwide, as of April 4. Researchers factored in population size, the number of hospital beds, the number of individuals tested, weather, plus some “socioeconomic and behavioral variables” like smoking.

That data was checked against county-level data on long-term exposure to PM2.5, which is generally measured by microgram per cubic meter of air.

According to the findings, an increase of just one microgram per cubic meter of air was associated with a 15% increase in the COVID-19 death rate.

L.A. County is dark red, indicating high particulate matter

“The results of this paper suggest that long-term exposure to air pollution increases vulnerability to experiencing the most severe COVID-19 outcomes,” the authors wrote.

The study has been submitted to The New England Journal of Medicine for review.

What is particulate matter?

The Environmental Protection Agency describes PM2.5 as “fine inhalable particles, with diameters that are generally 2.5 micrometers and smaller.” Most PM2.5 comes from emissions generated by cars and trucks, power plants, and industrial sites.

Exposure to particulate matter has been linked to harmful health conditions including asthma, decreased lung function and complications for people with heart or lung disease. Many of those same conditions put people who contract COVID-19 at a higher risk of falling severely ill, according to the CDC.

“There is a large overlap between the diseases that are affected by fine particulate matter and diseases that lead to death if you get COVID-19,” said Dr. Francesca Dominici, a professor of biostatistics at the Harvard T.H. Chan School of Public Health and the study’s senior author.

Dominici said the findings can serve as a guide for public health officials to strengthen distancing efforts, direct resources and prepare for more serious COVID-19 cases in regions with worse PM2.5 pollution.

Air pollution in southern California

Southern California skies may be remarkably clear right now, but our infamous air pollution is well documented.

The American Lung Association releases an annual “State of the Air” report, ranking U.S. counties and metropolitan areas with the worst air pollution. The Los Angeles-Long Beach metro area placed fifth in its most recent report for highest annual levels of PM2.5. Fresno and Bakersfield were ranked first and second, respectively.

Measuring by county, San Bernardino and Riverside counties placed sixth and eighth, respectively, for the U.S. counties with the highest year-round PM2.5 pollution. L.A. County ranked 15th. Thirteen of the 20 worst counties for PM2.5 levels were in California.

Dominici singled out L.A., Orange and Fresno counties as “among the most polluted counties in the United States” based on her team’s research.

“For California counties that are most polluted, what it means is that… unfortunately, we’re expecting higher risk of death [from] COVID,” she told LAist today. “You are dealing with a population that is already susceptible to adverse health effects of COVID, because their lungs have been already exposed to many years of fine particulate matter.”

San Bernardino and Riverside counties also lead the nation in ozone pollution levels, better known as smog. L.A. County is ranked third for a SoCal hat trick.

Harvard’s study did not examine ozone levels for possible links to COVID-19 mortality, but Dominici said her team plans to study that soon. She said she also wants to look further into the impact coronavirus is having on African Americans.

Harvard’s study is online and available to the public.

(Infographic by Riley Anderson)

LA Metro’s Idea of Solving Traffic: Making You Pay for It

LOS ANGELES — Good news, drivers. Metro is looking into the one solution that has actually been proven to reduce traffic.

Los Angeles County’s transit agency is set to vote this week to study a practice called “congestion pricing,” which would charge people to drive on roads based on how busy it gets.

Metro CEO Phil Washington proposed the idea last month as a way to not only reduce impassable roads, but accelerate some big transportation projects for the 2028 Olympics.

“We have to do something about congestion in the county and it’s going to get worse,” Washington told KPCC’s AirTalk in December.


If you’ve ever been hit with surge pricing while using a ride-hail service like Uber or Lyft, or tried the express toll lanes on the 10 or 110 freeways, you get the gist of congestion pricing. Users get charged a fee that goes up or down based on demand for a limited commodity, in this case the roads.

Metro is looking at three distinct models for congestion pricing:

  • The first, cordon pricing, is the most common in practice. It sets a variable fee to enter a certain neighborhood, usually the central business district, as is done in London and Stockholm.
  • The second model charges drivers based on the number of miles they travel, with rates dependent on the time of day and where the travel occurred.
  • Under the third model, drivers are charged on certain busy corridors, like freeways or big arterials, such as Wilshire Boulevard.

In all cases, the fee would vary according to the size of the demand. Driving at 8:30 a.m. would cost much more than at 10:30 p.m.

The idea is to force people to consider whether they really need to travel into a crowded area or at a peak time, or whether they might travel at a different time or elsewhere, or use a less costly alternative mode of transportation.


“The reason that people like me and my colleagues like congestion pricing so much is that it really is the only way to meaningfully reduce traffic congestion,” said Michael Manville, UCLA urban planning professor, at a Metro committee meeting in January.

“Conceptually, it’s the only way to do it. Empirically, it’s the only policy that’s ever been shown to reduce congestion and keep it reduced,” said Manville, pointing to successful programs in London, Stockholm, Milan and Singapore.

In London, the number of private cars entering the congestion zone dropped by 39 percent between 2002 and 2014. In Stockholm, traffic dropped by 20 percent during the 2006 pilot program, enough to convince a skeptical public to vote and make the charge permanent.

New York City has been working on some form of congestion pricing for years.

Manville also pointed to evidence that efforts to expand road capacity, by building more or bigger freeways or taking some cars off the road by building trains, don’t permanently reduce traffic. In most cases, these increase it.

“What basically happens is that you can have a situation where suddenly the road’s moving faster, but pretty soon people realize that, and they start to converge on the road at that time,” said Manville.

(Kevork Djansezian/Getty Images)

It’s such a well-documented phenomenon that it has a name: the Fundamental Law of Road Congestion — and we’ve written about it here.

Congestion pricing operates on basic economic theory. If there’s a high demand for a commodity and you give it away, people will get in line to get it and “pay” with their time instead. Soviet bread lines or free ice cream cones show how this plays out.

But if you set the price of a commodity correctly, you can mitigate the demand for it, and in the case of the roads, make them function more efficiently.

Many people are understandably resistant to the idea of paying for something they currently get for free. Until now, it’s been pretty difficult for congestion pricing to get political traction in the U.S., or be taken seriously by decision-makers.


Theoretically, yes. Gas taxes are intended as user fees that pay for the construction of roads, although technically our gas taxes haven’t actually paid for the roads in quite some time.

In Los Angeles County, residents also pay higher sales taxes to fund transportation, thanks to four voter transportation tax measures approved in recent years.

Manville said we could think of congestion pricing as metering road use, the way we meter the use of services like electricity or water. Once the pipe system or the electric grid is built and paid for, utilities don’t stop charging people to use the service. If they did, people would leave their water on for 10 hours or run their air conditioners all day.

“One thing that price does that the gas tax does not do is not just make sure that the service is there but that it’s good service,” he said.

Under Manville’s analogy, the roads are like the water service. We only have enough of it to allocate well, and it’s only allocated well if it’s priced right.


A cordon or corridor system would likely require all cars to carry a transponder, such as the FasTrak currently used for the express lanes. A charge based on vehicle miles traveled could be viewed as more invasive, requiring some kind of location-enabled tracking that plugs into a car’s computer.

Metro has already had a hard time enforcing tolls in its express lanes, admitting a full quarter of users evade payment by switching their transponders to carpool or avoiding transponder readers. Metro is pursuing video systems that can read the number of passengers to catch carpool cheaters.


This is an oft-cited criticism. The fact is the charges would disproportionately burden lower-income people.

Manville pointed out that we accept many other regressive charges, such as those for utility bills, gas taxes and transit sales taxes but that there are many ways to mitigate the negative effects for disadvantaged populations. Offering a low-income discount, as Metro does for transit fares, is one.

The revenues from congestion pricing can also be reinvested into alternative modes of transportation like transit to make non-auto travel more viable. And with reduced traffic, buses can operate much more efficiently.

Metro’s Washington has even suggested that county transit could be offered free with revenues from congestion pricing. Metro estimates congestion pricing could raise about $10 billion a year.

“If we were to implement something like this, we would be the first major city in the world that would offer free transit on the scale that we have it here in Los Angeles,” he said.