Tiny particles in smoke from wildfires may increase the danger of acute heart problems, including cardiac arrest and ischemic heart disease, especially among vulnerable people, according to a new study published today in the Journal of the American Heart Association.
The findings are especially worrisome as heavy smoke generated from wildfires in Alaska and Canada continues to drift southward. Smoke already has made its way down into the northern United States, including Montana, the Central Plains, the Upper Mississippi Valley, and into the Mid-Atlantic and Northeast.
“During bushfires there is widespread and huge quantities of smoke, and people are exposed,” said Anjali Haikerwal, study author and a doctoral candidate at the school of public health and preventive medicine at Monash University in Melbourne. “These particulates can be easily inhaled deep into the lungs. These particles may act as a trigger factor for acute cardiovascular health events.”
The new research studied the connection between exposure to wildfire-related fine particulate pollution — particles smaller than 2.5 thousandths of a millimeter in diameter, which is 1/30 the diameter of a human hair — and the risk of cardiac incidents in the state of Victoria, Australia in December 2006 and January 2007. During the two-month period, smoke reached cities far from the blazes and, on most days during the wildfires, levels of particles exceeded the recommended air quality limits.
Examining Victoria health registry data during the wildfires, the scientists found a 6.9 percent increase in out-of-hospital cardiac arrests, with a stronger link between pollution and cardiac arrests in men and individuals 65 and older. They also found a 2.07 percent increase in emergency department visits for ischemic heart disease and a 1.86 percent increase in hospitalizations for ischemic heart disease, with a stronger association in women and those 65 and older. Ischemic heart disease manifests as reduced blood flow to the heart.
“This new study suggests that particles from wildfires specifically can cause adverse cardiovascular effects on a short-term basis,” said Jonathan Samet, professor and chair of the department of preventive medicine at the University of Southern California’s Keck School of Medicine. “This is a useful finding from the public health point of view and suggests that we should alert the public and the medical care system about this risk.”
Samet has conducted research on the health risks of inhaled pollutants, including particles and ozone in outdoor air, and was not involved in this study. He called the new paper “a demonstration that particles from forest fires can cause adverse effects on cardiovascular health.”
“The advance is in showing the risks of particles from one particular source — forest fires — that can lead to widespread population exposures,” he said.
Recent decades have shown a steady increase in wildfire activity in the United States. Annual wildfire costs increased to $3 billion in the early 2000s, up from $1 billion in the 1990s. The area burned during that time period doubled, rising to 6.5 million acres, up from 3.6 million. A report recently released found that between 7 and 9 million acres were burned annually in the United States.
This current year has been especially bad. As of June 30, nearly four dozen wildfires burned from Alaska down to Arizona and as far as Colorado. Wildfires in Southern California have driven thousands from their homes, while fires in Alaska have destroyed more than one million acres. Thousands of people have been evacuated because of the hundreds of fires burning across Canada’s western provinces and the thick smoke they produce. Air advisories have been issued across central and western Canada, as well as parts of the western United States. During the last two weeks, about 13,000 people have left their homes from about 50 communities in Saskatchewan. Fires have destroyed 81 houses and cabins. Earlier this week, 127 fires were burning, half of them near La Ronge, a town of 2,700 and one of the largest communities in northern Saskatchewan.
Many climate scientists believe this upsurge is the result of climate change, which contributes to conditions that encourage wildfires. Heikerwal, the study’s author, acknowledged a possible link. “We are living in this world and seeing heat waves and drought happening around us so, yes, it could be climate related,” Heikerwal said.
Climate change alters the conditions that trigger fires or determine their intensity, including how much fuel is available, how fires are ignited, and how flammable the fuel is that keeps the fires burning. By influencing storm patterns, for example, global warming may change the frequency of fires started by lightning. Climate also affects the structure and composition of forests, generally increasing the amount of fuel available to burn. Other climate variables that occur on a shorter time scale play a role, like higher temperatures, lower humidity, and stronger winds. These all increase the ease with which fires are started and facilitate the spread of wildfires.
Through shifting precipitation patterns, more frequent drought and higher temperatures, global warming has increased the risk of wildfires. Moreover, hotter temperatures have led to wildfires starting in previously wildfire-free locations like arctic Alaska and the southwestern deserts.
Furthermore, extended periods of record-breaking temperatures and drought create drier conditions that in turn make wildfires bigger and lengthen the wildfire seasons. The western United States has experienced this unfortunate phenomenon, as large wildfires have grown more frequent and the fire season has grown significantly longer in recent decades. The main drivers of this increase are considered to be higher temperatures and earlier spring snowmelt.
“Living in California, I am very aware of the issue of drought and forest fire danger,” Samet said. “The IPCC does project increased risk for forest fires as some areas become drier. Of course, it is difficult to attribute specific events directly to climate change, but the prolonged drought in California and the western U.S. is considered by many to be a reflection of climate change.”
A recent report found that as the global average temperature has increased over the last 35 years, the wildfire season has gotten longer, and the global area affected by them has doubled.
“As a generality, increasing population exposure to smoke from fires would be expected to increase risk for cardiovascular events, though the increases would likely only be detected through complex analytical approaches, unless truly catastrophic — like the London Fog of 1952,” Samet added, referring to the toxic smog that smothered England’s capital city for five days in December of that year, killing thousands.
Haikerwal called for more research to determine the danger posed by smoke that travels far from its original source. “These particles are so small that they are suspended in atmosphere for long periods, and might have the potential to locate to other places,” she said. “But we don’t know how far, or how near.”
In the meantime, given the increase in frequency and intensity of wildfires experienced in recent years in the United States and elsewhere, she urged those exposed to smoke to be aware of its health impacts, and be vigilant to such symptoms as chest pain and tightness, shortness of breath, dizziness, and coughing, all signs of possible heart trouble.
“These are the symptoms to be mindful of during this period,” she said. “Do not delay seeking medical help if you experience symptoms of heart problems during smoke episodes from wildfires.”
Marlene Cimons, a former Los Angeles Times Washington reporter, is a freelance writer who specializes in science, health, and the environment.