Julio Díaz
Research professor and co-director of the Reference Unit on Climate Change, Health and the Urban Environment at the Carlos III Health Institute
In my opinion, this is an interesting study that highlights the importance to health of exposure to smoke from forest fires that have occurred hundreds or even thousands of kilometres away from the place where it is focused. In this case, it refers to the impact of fires in Canada on mortality in Europe and North America.
Although the article appears robust from the point of view of smoke transport models from these fires, from the point of view of health impact, there are two issues that could be improved in the manuscript.
On the one hand, the impact of PM2.5 is estimated using standard functions for PM2.5, without taking into account the composition of PM from forest fires, which tends to be more toxic and therefore has greater health effects.
On the other hand, PM2.5 is often associated with volatile organic compounds that act as precursors to tropospheric ozone, so the health impact of this other secondary pollutant should be added to the impact of PM. This tropospheric ozone has a health impact that is sometimes greater than that of PM itself.
Therefore, the figures given in this study on the health impact of these Canadian fires on North America and Europe are probably underestimated.