Study suggests link to persistent fire smoke and spread of COVID-19

Photo: Alanna Kelly

A firefighting helicopter in the smoke over Cache Creek on Thursday

A recent study has suggested there could be an association between persistent wildfire smoke and the spread of COVID-19.

The study recently published in the Journal of Exposure Science and Environmental Epidemiology used data collected in Nevada last year.

It found a 17.7 per cent increase in COVID-19 cases, possibly caused by PM2.5 pollution, when smoke blanketed the city between Aug. 16, 2020 and Oct. 10, 2020.

PM2.5 particulates found in fire smoke have a diameter of less than 2.5 micrometres. It travels deep into the lungs and causes damage.

“Our results showed a substantial increase in the COVID-19 positivity rate in Reno during a time when we were affected by heavy wildfire smoke from California wildfires,” study lead and co-author Daniel Kiser told the Reno Gazette Journal.

Kiser said he was inspired to study the subject after reading a B.C. scientist’s article on the two crises.

“As we enter the wildfire season in the northern hemisphere, the potential for a dangerous interaction between SARS-CoV-2 and smoke pollution should be recognized and acknowledged,” said BC CDC senior scientist Sarah Henderson in her work that inspired Kiser.

“This is challenging because the public health threat of COVID-19 is immediate and clear, whereas the public health threat of wildfire smoke seems distant and uncertain in comparison. However, we must start preparing now to effectively manage the combination of public health threats.”

The study data did not support same-day association between COVID-19 test positivity and PM2.5, but found that the increase in cases was most strongly associated with dense smoke two to six days prior.

“Although this study only evaluated positivity rates, it is reasonable to assume that the excess cases due to wildfire PM2.5 resulted in excess mortality,” the study states.

Even with the widespread rollout of vaccines, the study predicted that fire season would again coincide with the pandemic in 2021.

“Thus, our findings should help shape regional policies that seek to manage the combined threats of wildfires and the pandemic,” the study continued.

“These policies might include lowering the recommended healthy limit for PM2.5 in cities with a high prevalence of SARS-CoV-2, establishing ‘clean air’ shelters that maintain social distancing, and allocating sufficient quantities of appropriate respirators to areas at high risk for wildfires.”