The timing is uncanny: as wildfires continue to rage throughout California and smoke from forest fires in western Canada drifts as far as the east coast of the United States, the Journal of the American Heart Association has just published a new study that reveals that air pollution from wildfires may lead to an increased risk of acute heart problems.
Wildfire smoke has long been linked to asthma and other respiratory conditions, but scientists have only recently been able to consistently demonstrate the connections between wildfire smoke exposure and heart problems. This new study, authored by doctoral candidate Anjali Haikerwal of Monash University’s School of Public Health & Preventive Medicine in Melbourne, Australia, joins a growing body of current research exploring the effects, both short and long term, of fine-particle air pollution from wildfire smoke on the heart.
The study covers the months of December 2006 and January 2007, when a series of bushfires in the state of Victoria, Australia, burned between 1.2 and 1.3 million hectares of land. The resulting smoke haze affected traffic, delayed flights to and from Melbourne’s airport, and forced a ban on outside play at some schools. According to Australia’s Environment Protection Authority, December 20 saw the worst levels of bushfire smoke ever recorded in the country, with visibility in the central business district of Melbourne reduced to just two kilometers.
The specific aim of the study was to examine the association during this period between the risk of heart-related incidents, such as cardiac arrests, and the fine particulate matter air pollutant produced by the bushfires. Typically not visible to the human eye, these fine particles measure less than 2.5 thousandths of a millimeter in diameter, or just 1/30th of the diameter of a human hair. Haikerwal and her research team used modeled air exposure data to estimate the bushfires’ levels of fine-particle concentration, which were then examined alongside additional health registry data from the state of Victoria for the same period.
The results do seem to indicate that air pollutants from wildfires can play a role in triggering acute heart problems. The study’s most significant finding was that out-of-hospital cardiac arrests increased by nearly 7% when particle concentration increased from the 25th to the 75th percentile over two days (including adjustments for humidity and temperature). In addition, the association between cardiac arrests and pollution was found to be stronger in men and people over the age of 65. The study also found an increase of just over 2% in emergency department visits for ischemic heart disease, a heart problem caused by narrowing heart arteries that prevent adequate blood and oxygen from reaching the heart, and an increase of nearly 2% in hospitalizations for the same condition, this time particularly among women as well as people aged 65 and over.
The study further emphasizes that, while these findings are consistent with other research and do constitute a demonstrable association between fine-particle exposure and acute heart problems, additional research is still needed to determine how exactly air pollutants affect the cardiovascular system in these cases. One leading explanation suggests that inhaling the particles causes inflammation and nerve irritation in the lungs, which in turn can disrupt the balance of the body’s nervous system, leading to responses such as elevated blood pressure and interrupted cardiac electrical activity, which then provoke cardiovascular events like cardiac arrest.
Given the extent of the wildfires currently burning in North America, as well as the fact that wildfire smoke disperses widely and has the potential to affect large portions of the population well away from the actual source of the fire, it is crucial for the general public to be aware of the health implications of Haikerwal’s study. Among the most significant of these is the fact that seniors are at particularly high risk for acute heart problems triggered by fine particles. It is also important to note that the length of exposure to elevated levels of particle concentration does not need to be very long—two days was the time frame used in the study—to trigger an acute cardiovascular health event.
In the event of a wildfire situation, Haikerwal urges people to protect themselves by following precautionary measures set out by local public health officials, and to seek help immediately if they experience symptoms of heart problems following smoke exposure. To further help people stay informed and healthy, the US Environmental Protection Agency posts daily updates on air quality and levels of particulate matter on its website.