California Wildfire Smoke Harms Respiratory Health More than Fine Particulates from Any Other Source, Including Vehicle Emissions

By Jerri-Lynn Scofield, who has worked as a securities lawyer and a derivatives trader. She is currently writing a book about textile artisans.

A new study has found that the smoke that now blankets large parts of California during wildfire season is more toxic to human respiratory systems than any other source of fine particles, including vehicle emissions.

The study, published last week in Nature Communications, covered the period from 1999 through 2012 and examined data for southern California. It concluded that toxic particles arising from wildfires were ten times more likely to lead to hospitalizations than those from any other source.

The study concluded that given the different toxicity of particulate matter – depending on its source – policymakers needed to consider the source of emissions when formulating air quality standards:

Wildfires are becoming more frequent and destructive in a changing climate. Fine particulate matter, PM2.5, in wildfire smoke adversely impacts human health. Recent toxicological studies suggest that wildfire particulate matter may be more toxic than equal doses of ambient PM2.5. Air quality regulations however assume that the toxicity of PM2.5 does not vary across different sources of emission. Assessing whether PM2.5 from wildfires is more or less harmful than PM2.5 from other sources is a pressing public health concern. Here, we isolate the wildfire-specific PM2.5 using a series of statistical approaches and exposure definitions. We found increases in respiratory hospitalizations ranging from 1.3 to up to 10% with a 10 μg m−3 increase in wildfire-specific PM2.5, compared to 0.67 to 1.3% associated with non-wildfire PM2.5. Our conclusions point to the need for air quality policies to consider the variability in PM2.5 impacts on human health according to the sources of emission.

This conclusion is particularly important as California has always led the way among U.S. states in formulating air quality standards.

Climate Change Effects

Climate change has only raised the importance of these issues. Wildfires will become an increasingly common feature as the effects of climate change increase. According to The Guardian:

“We know wildfires are going to become more extreme, due to climate change,” said Rosana Aguilera, a postdoctoral scholar who co-authored the research. “And it’s important that we start to reckon with the health effects of that.”

Aguilera and her colleagues looked at hospital admissions over a 14-year period, from 1999 through 2012, and found that spikes in air pollution during peak fire season in southern California – when fierce Santa Ana winds usually stoke the most destructive wildfires – were correlated with a 10% increase in hospitalizations for respiratory issues.

Since then, wildfires in the west have only gotten more ferocious and destructive – spewing up even more toxic smoke. Six of the largest wildfires on record burned in 2020. And while particulate pollution across the US has been generally declining in recent years due to stricter environmental regulations, pollution in the north-west increased due to wildfires.

Impact of Wildfires on Low-Wage Workers

The Guardian account emphasised the disparate impact of the wildfires on low-wage workers, especially those required to do hard physical labor outdoors during fire season:

The pollution disproportionately impacts low-wage workers, and poor communities of color across the state who are already exposed to high levels of pollution from other sources including factories, highways and refineries. In southern California’s Riverside and Imperial counties, southeast of Los Angeles, farmworkers regularly breathe in pesticide-laden smog. “In our region, the majority of workers have asthma,” said Luz Gallegos, the executive director of the advocacy group Todec. “Their kids have asthma, their parents have asthma. This has been an ongoing crisis.”

During last year’s record-setting wildfires, workers continued to harvest crops under smoke-filled skies. “One woman in our community just collapsed in the field, as she was working,” Gallegos said. She had asthma, and once she was rushed to the hospital, tested positive for Covid-19. “Thank God, she survived,” Gallegos said – but it’s uncertain whether her lungs will be able to handle the continued strain.

“These stories are very, very common,” Gallegos added.

Implications for a Post-COVID World.

The study carries worrying implications  for a post-COVID world, for three reasons. Worsening wildfires will be an increasingly familiar occurrence as climate change accelerates. Even with drastic policy changes, even best case scenarios don’t predict any reversal of climate changes already set in motion.

First worry: many Californians who have survived COVID-19 now suffer impaired lung function, whether they experienced acute symptoms or not. A reminder: these impacts are not confined exclusively to the elderly or otherwise infirm. During an appointment with my opthalmologist in January, I got to taking to the technician who administered some of my eye tests. He was in his early twenties and looked quite fit. He confided that he’d had COVID late in 2020 – what he called a bad case, although I don’t think he was hospitalized – and was just beginning to feel better, after months of recovery. He said he was worried as scans of his lungs showed lingering damage. He said he’d always been active – a runner maybe? I don’t recall exactly. But he was young and lean. I know this is only one example, but there are so many more.

Second worry: the study looked at California only, from 1999 through 2012, stopping nearly a decade ago. Since then, West Coast wildfires have only dramatically worsened. And in future, out- of- control wildfires won’t be confined to the U.S. alone. Other places will – and some already have – experienced them. Take, for example,  Brazil; I wrote about the wildfires then raging in its Pantanal wetland – a place that should be impervious to wildfires – last September (see Brazil’s Pantanal Wetland is On Fire, Joining Other Places Where Wildfires Rage or Have Recently Burned Out of Control). The Pantanal is typically flooded between November and April, during the Brazilian rainy season .

Note that Brazil has also been hard-hit by COVID – and the ravages of the disease have also left many survivors with damaged lungs.

Third, worry: although this study examined the impact of wildfires on respiratory illnesses only, the smoke they produce can also drastically afflict  those who suffer from cardiovascular disease, and thus increase the likelihood of heart attacks or strokes. The Guardian picked up on this point:

Recent research has shown that wildfire smoke can exacerbate not only respiratory illnesses but also heart conditions – triggering heart attacks and strokes, said Mary Prunicki, a Stanford researcher who studies the health impact of air pollution.

Prunicki, who was not involved in the recent study, said there is a growing body of evidence that smoke from the megafires California has seen in recent years is not only bad for our health, it’s “extra-bad – probably worse than some other types of pollution”.

Impaired heart and brain function has also been reported in some COVID survivors.

What Is To Be Done?

The Guardian gestured to the need for California to adopt better wildfire policies. This is particularly important in a post-COVID world, where many people will be less able to cope with the smoke wildfires produce:

Although wildfires are a natural part of California’s landscape, global heating and decades of forest mismanagement have left the region increasingly vulnerable to bigger, more destructive blazes. Researchers said that officials should immediately take steps to curb greenhouse gas emissions to address the climate crisis, and recognize Indigenous ecological expertise in managing fire-prone landscapes.

Solutions could include a return to “prescribed burns” – a technique that hundreds of California’s Native people have used for thousands of years, setting small controlled burns to clear out fire-fueling vegetation and prevent the larger, more toxic blazes that have obliterated homes and neighborhoods.