COPD outlook DAVID GRAY/GETTY DAVID Firefighters battle the bush fires that devastated Australia in 2019 and 2020. leads to faster lung-function decline even in people with otherwise healthy lungs. “Other Fireproofing the lungs parts of the world, I think, should be watch- ing very closely,” says Wark, particularly the wildfire-prone US west coast. People with conditions such as COPD are vulnerable “I find it rather unsettling that there are all these unknown things,” says Guy Marks, to wildfire pollution, but there is little advice on how a respiratory and environmental epidemiol- to keep safe. By Anna Nowogrodzki ogist at the University of New South Wales, Sydney. “The scale of the fire that we’ve just had is unprecedented. It represents to me a few days into the new year, an older prednisone on hand to ease her symptoms. clear turning point in our experience of the person came into John Hunter But still, she found breathing more and more consequences of climate change.” Hospital in Newcastle, Australia, difficult. wheezing and short of breath. Res- COPD is a common condition — it is the third Vulnerable lungs piratory physician Peter Wark was leading global cause of death. And people with Wark’s patient improved just by being in the Aon call at the time. He wasn’t surprised to respiratory conditions such as COPD are some air-conditioned hospital. “We really didn’t do see someone with respiratory problems — of the most vulnerable to particulate matter anything else,” he says. She was one of three or Australia was enduring an unprecedented and from air pollution and wildfires. Data from pre- four older people with lung disease whom Wark devastating bush-fire season. Smoke from fires vious Australian bush fires, as well as wildfires remembers arriving at the hospital over the that had been raging kilometres away for the in California, Colorado and North Carolina, course of a few days. But he strongly suspects past four weeks had caused the air quality in show that people who have COPD visit the that many more people with respiratory dis- the city to plummet. emergency department more frequently than eases were suffering. “The ones who make it to Wark’s patient already had chronic obstruc- usual during these events. the hospital are the tip of the iceberg,” he says. tive pulmonary disease (COPD), and her med- Yet physicians don’t have the evidence they Wildfires are not good news for people with ical team had tried to prepare her for this kind need to tell these vulnerable people what to COPD. A 2019 review found evidence across of event. She had done her best to keep her do to protect their health. And researchers multiple studies that visits to emergency windows and doors closed, despite a lack of don’t know what the effect of this exposure will departments increase for people with COPD1. air conditioning and some brutally hot days. be for everybody in the long term. Data sug- However, the data on hospitalization were And she had the anti-inflammatory drug gest that long-term exposure to air pollution mixed. Some studies found an association S18 | Nature | Vol 581 | 14 May 2020 ©2020 Spri nger Nature Li mited. All ri ghts reserved. ©2020 Spri nger Nature Li mited. All ri ghts reserved. between wildfire smoke and hospitalizations Poorly maintained properties and older mask to ensure that it filters out particles as it overall, and others did not, says Colleen homes tend to be leaky and let in smoke even is supposed to. Marks says there’s not enough Reid, a health geographer at the University of with windows and doors closed, she explains. evidence to say whether N95 masks are bene- Colorado Boulder and an author of the review. And people without air conditioning often ficial for people with COPD. One study found The most concerning pollutant for those leave their windows open. A study of indoor that, for 14 people with mild COPD, wearing who find themselves downwind of a wildfire is air quality during the 2016 and 2017 wildfire either an N95 mask or a mask that covered half fine particulate matter less than 2.5 microns in seasons in Denver, Colorado, found that most the face affected breathing — in particular by 6 diameter, says Reid. These PM2.5 particles are of the 28 low-income homes studied kept a limiting how quickly the person could exhale . about four times smaller than a grain of pollen. window open for more than 12 hours a day, Although it’s not clear how people with In a 2019 paper, Reid found that PM2.5 levels which more than doubled the levels of some COPD can protect themselves from the effects increased sixfold downwind of a wildfire, pollutants in their homes4. of smoke particles, medical interventions whereas levels of ozone — another pollutant can help them if their symptoms worsen and that can harm the lungs — increased less than breathing becomes more difficult. Ipratropium 2 “There could be a different twofold . chemical composition of the bromide and β-adrenergic agonists such as PM2.5 travels farther into the lung tissue salbutamol can be taken to widen the bron- than larger particles, almost reaching the smoke depending on what’s chi. And prednisone — taken orally to reduce tiny grape-like sacs called alveoli where gas being burned.” inflammation — helps some people. A 2003 exchange happens, says Nicholas Kenyon, a study of people who had recently been dis- pulmonologist at University of California, charged from hospital following an exacer- Davis. He says that in vitro experiments sug- If people do shelter in place, evidence bation of COPD showed that those who took gest that, once in the lung tissue, the particles suggests that air purifiers such as prednisone for 5 days were considerably less exacerbate chronic bronchitis (inflammation high-efficiency particulate air (HEPA) filters likely to visit an emergency department within of the airways) and disrupt the layer of epithe- in the home decrease particulate-pollution 30 days than were those who did not take it7. lial cells that line the airways. levels, says Reid. It is less clear whether puri- However, these strategies have not been tested It isn’t clear exactly which chemicals in PM2.5 fiers improve the respiratory health of people specifically in people with acute severe smoke affect lung tissue, says Reid. “There could be a with COPD. One study of 35 people with COPD exposure in controlled trials, says Wark. different chemical composition of the smoke found that HEPA filters had no effect on res- If needed, oxygen therapy and antibiotics depending on what’s being burned,” she says. piratory symptoms when used for 6 weeks5. can be provided in hospital, so it is also advised Various studies have implicated different sets Still, the reduction in particulates in the home that people with COPD who live in at-risk loca- of chemicals in lung problems. is reason enough for many clinicians to rec- tions have an action plan for getting to a med- Scientists also don’t know enough about the ommend purifiers — especially to people who ical centre during a wildfire. health impacts of ozone produced during wild- live very close to busy roads or notice soot on Wildfires are short-term events, but climate fires, Reid says. Ozone causes airway inflam- their windows. “I encourage them to get air change is already increasing their frequency, mation and the formation of very unstable and purifiers,” says Mary Rice, a pulmonary and meaning that people in fire-prone areas will highly reactive molecules. These free radicals critical care physician at Beth Israel Deaconess probably be exposed to wildfire smoke more can kill the lungs’ epithelial cells, stripping the Medical Center in Boston, Massachusetts. often. There are few studies of the long-term airways and leaving the lung tissue more vul- The costs can add up quickly, however, health impacts of repeated wildfire-smoke nerable to viruses or allergens, says Kenyon. putting HEPA filters out of reach for people exposure on either healthy people or those Research has found that higher ozone levels with low incomes. Air purifiers cost US$100– with COPD. But more generally, Rice says that are correlated with increased hospital admis- 600 in the United States. When used contin- long-term exposure to air pollution allowable sions and emergency-department visits for uously, HEPA filters (costing $90–175 each) within the current US Environmental Protec- people with COPD3. need to be replaced every three months and tion Agency standards “is associated with use about $30–90 of electricity per year — more rapid decline in lung function”. Uncertain response although running a purifier only during wild- “I find myself rather frustrated at not There isn’t enough research into how to protect fires would cost less. And each room requires having the answers,” says Marks. As a COPD the health of people with lung conditions from its own purifier. researcher, he says, “I get frequently asked, the spiralling effects of climate change, says When the smoke pollution is particularly ‘What are the risks and what should we do to Rupa Basu, an epidemiologist in the Office of bad, many people use N95 particulate respira- protect ourselves?’ And I give more or less the Environmental Health Hazard Assessment tor masks. These fit tighter than surgical masks same answer: that we don’t really know.” at the California Environmental Protection and are designed to keep out particles as small Agency in Oakland. “Sometimes people look as 0.3 microns — more than eight times smaller Anna Nowogrodzki is a journalist based in at all respiratory disease, which may not be than PM2.5.