Long-term smoke exposure may be associated with dying from a tumour: study

Amid some of the worst air quality to hit North America in decades, a new study has dug into the long-term health impacts of smoke exposure.

While researchers didn’t find any significant associations between wildfire-related air pollution and increased mortality from cardiovascular or respiratory diseases, they did find an association between this exposure and mortality due to neoplasms— another term for tumours.

Authors say that the new research, published this month in the peer-reviewed Journal of Hazardous Materials, is the first of its kind.

“To the best of our knowledge, this is the first population-based prospective cohort study to quantify the associations between long-term exposure to wildfire-related PM2.5 and mortality,” Shanshan Li, associate professor at Monash University in Australia and lead researcher, said in a press release.

It’s a timely study. Wildfire smoke has left huge swathes of North America choking for air over the past few months, with many of the strongest blazes burning in Canada. Dangerous air quality warnings were issued in parts of Ontario and Quebec Sunday as smoke and ash continue to clog the sky.

“Given the recent pollution levels in North America caused by the Canadian wildfires, our study linking long-term exposure to wildfire-related PM2.5 and mortality suggest that further research is urgently needed to provide more scientific evidence on this topic,” Li said.

PM2.5 refers to fine particulate matter that is 2.5 microns or less in diameter. It is an air pollutant usually found in wildfire smoke that causes air to appear hazy when levels are high. When a large quantity of it is inhaled, it can cause short-term damage such as eye, nose, throat and lung irritation, as well as longer-term damage to the heart and lungs, according to previous research.

This new study took health data from the U.K. Biobank, a cohort of more than 492,000 participants enrolled between 2004 to 2010, and followed participants for around 11 years.

Researchers looked at which participants had passed away during the scope of the study period, regardless of the their cause of death, and then mapped out their exposure to wildfire-related PM2.5 one to five years before their death.

They then investigated to see if the level of exposure showed any patterns connected to different types of mortality — essentially, whether participants who died of certain diseases tended to also have a higher level of wildfire smoke exposure that could underline an association of risk.

While there was no particularly strong association with cardiovascular or respiratory deaths, Li said the study findings “show that wildfire-related PM2.5 exposure has long-lasting adverse impacts on all-cause, nonaccidental, and neoplasm (tumour) mortality.”

All-cause mortality means that when looking at all deaths, before separating them by case, long-term smoke exposure was found to be associated with an increased risk of death in general.

One of the reasons that inhaling PM2.5 may have an impact on the formation of tumours, the study suggested, is that previous research has shown that it can cause slight alterations in the body, including activating tumour-associated signalling pathways.

Authors noted that the study has its limitations, including that the U.K. isn’t as prone to severe wildfires as some other regions of the world, meaning these associations could be more dire in regions that see heavier wildfire activity. They also note that more research needs to be done to better underline how smoke exposure may be associated with mortality.