No, Air Pollution Isn’t Much Better

Newspapers around the world have delivered a glimmer of positive news by reporting physical distancing’s seemingly rapid environmental benefits. Keep the humans indoors and shut down the economy, such stories suggest, and the world quickly returns to a clean and natural state. Closer analysis, however, reveals many of the rebounds to be wishful thinking. The dolphins allegedly rushing to Venice’s cleaner waters were, in fact, filmed in Sardinia.

Some reports attributing clean air around the world to reduced traffic and idle industries may be equally unfounded, that includes rosy reports that British Columbia’s skies cleared over the past month thanks to the shuttering of non-essential businesses and travel, and the need to physically distance from each other. Our research reveals that British Columbia’s most harmful air pollution — fine particles of soot and dust — has likely been more prevalent than average compared to the past five years.

“If you look at the soot levels, which is what we’re most concerned with, there’s not much indication that they’ve gone down,” says Michael Brauer, a professor at the University of British Columbia’s School of Population and Public Health who studies the health impacts of air pollution.

Environmental health experts such as Brauer say enduring air pollution is likely making people with COVID-19 more sick, and increasing B.C.’s pandemic death toll. The province has taken some actions, including banning most outdoor fires to limit air pollution during the pandemic. But some experts are hoping for more, such as restrictions on the use of fireplaces and wood stoves.

By examining the latest data from pollution sensors around British Columbia, our analysis found some worrisome trends. We zeroed in on two pollutants: fine particulate matter, also known as PM2.5 because it includes airborne particles smaller than 2.5 microns (1/400th of a millimetre) across, and nitrogen dioxide, or NO2. Major sources of PM2.5 include diesel engines and burning wood, as well as dust from construction sites. NO2 is a reddish-brown gas created by vehicle engines and other high-temperature combustion sources.

To analyze that data, we took a different tack from most news reports crediting COVID-19 with decreasing pollution, which generally compare the days or weeks before and after physical distancing began. The Vancouver Sun recently did that, for example, reporting a “drop in PM2.5” in the Metro Vancouver region that it claimed was “plainly visible” in visualizations of sensor data from the regional authority’s air-map website.

Brauer says some of the recent before-and-after observations are likely accurate, such as those showing air clearing in heavily-polluted India and northern Italy. However, he warns that shifting weather can also clear the air — or intensify air pollution.

Meteorological conditions that trap air likely caused the pollution spike that Beijing experienced in mid-February, for example, when PM2.5 levels set a three-year record amid the Chinese capital’s pandemic lockdown.

Our analysis reveals the weather-driven variability of British Columbia’s pollution. We calculated the average PM2.5 and NO2 concentrations during the first month of distancing — March 15 to April 15 — at various sites around the province. We then compared pollution levels recorded during physical distancing against the levels observed over the same 31 days over the previous four years. The data shows substantial year-to-year variation. (See charts.)

Reduced car traffic should produce less NO2, and most sites we examined did come in slightly cleaner over the past month — with roughly seven per cent less NO2 than the 2016–2019 average. But every year was different, and most sites reported cleaner air than the past month for at least one recent year.

NO2 levels were higher than average at one site beside Vancouver’s Second Narrows Bridge. But Metro Vancouver air quality planner Kyle Howe says that site is a regular outlier. The sensor sits beside an industrial site, and even one idling truck can inflate its readings.

PM2.5, however, was consistently higher than average during British Columbia’s first month of COVID-19 distancing compared to previous years — three to 22 per cent higher at four of the sites examined. The fifth site showed little change from average conditions.

Brauer and Howe point out that one might expect residents cooped up at home to fire up wood stoves and fireplaces, creating more soot. But they say the modest PM2.5 increment above average our analysis detected under physical distancing — about 0.73 micrograms per cubic metre of air — could just as easily reflect natural variability. The variability we observed supports that soot levels vary by year even more than those for NO2, and at most sites at least one prior year had sootier air than 2020.

What is certain from the data is that British Columbia air is not pristine, and the pollution has health consequences for residents — especially those experiencing COVID-19. “We’re still seeing pollution and there’s no safe level. Air pollution worsens respiratory infections,” says Brauer.

Researchers from Harvard University recently estimated that every one microgram increase in soot concentration increases mortality from COVID-19 by 15 per cent. Brauer says a study of China’s 2003 SARS outbreak found similar increased deaths from air pollution.

The link between air pollution and respiratory disease is one reason why provincial health officer Dr. Bonnie Henry has advocated for bans on slash burning and other open fires during the pandemic, according to Sarah Henderson, senior environmental health scientist at the BC Centre for Disease Control. On March 26 the BC Ministry of Environment and Climate Change Strategy answered that call, announcing a temporary smoke control regulation for thickly populated areas, which the ministry subsequently extended through June 15.

Brauer says residential fires, especially in the Lower Mainland, should be banned unless wood burning is a home’s primary heat source. “The idea that people are lighting fires that can make someone’s infection bad enough that they go to the hospital is something we shouldn’t be allowing,” he says.

Late last month Metro Vancouver tightened its bylaws for indoor wood stoves and fireplaces — an update that was three years in the making. The new rules limit use of older, more polluting equipment and ban indoor wood fires during warm months — moves that the city projects will deliver over $282-million in health-related economic benefits, including reduced mortality. However, the rules do not begin phasing in until next May.

Henderson says BC residents living in urban areas should already be thinking twice about lighting up their fireplace, unless they need it to stay warm. “Using fireplaces for aesthetic value right now? No, I wouldn’t recommend that,” she says. And if people are going to burn, she says they should do so responsibly. “You can burn wood without making a whole ton of smoke.”

Her biggest concern, however, is the approaching wildfire season, which now begins as early as June thanks to climate change drying out British Columbia’s interior forests. Smoke from wildfires significantly affected Metro Vancouver’s air quality during the summers of 2015, 2017, and 2018, and fouled air considerably more in the province’s interior. In August of 2018, record PM2.5 levels placed Quesnel and Prince George among the world’s top 10 most-polluted cities.

This summer those spiking PM2.5 concentrations could be harder to escape for people with respiratory challenges. Dr. Henry recently suggested that some physical distancing measures will continue through this summer. Henderson says it may not be possible with ongoing COVID-19 concerns for people to retreat to malls, community centres, and other public gathering places with ventilation systems that provide cleaner air.

On April 16 additional burn limits went into effect province-wide designed to reduce the risk of wildfire this summer. Those limits rule out most open fires, but still allow campfires. That is, for now. The campfire exception, as with everything in COVID-19 time, is no doubt subject to change.