Linking climate change to health outcomes, a lunch time webinar series.

The health effects of landscape fire smoke depends on the intensity and duration of exposure. There are very many contaminants in smoke and these vary according to the stage of fire (smouldering or fully developed), they type of fuel and the transport of the smoke from the fire front to the population. The main pollutant used in health studies (and health warnings) is fine particulates. These are present in all fires. Again their composition (chemistry) varies but for monitoring and health studies fine particulates (as a single entity) is used. Therefore, it is the exposure to smoke per se, irrespective of the type of fire.

This comes mostly from large cohort studies, mostly birth cohorts, although there are some adult studies that are also showing the association between air pollution and asthma development. These studies are done in cities so the air pollution of concern is urban combustion pollutants (mostly traffic emissions). For many years air pollution has been accepted as a trigger for symptoms but the association with asthma initiation has been less clear.  However, there are now a number of longitudinal cohort studies showing relationships between early life or lifetime exposure and asthma development.

Pregnant women should be encouraged to reduce exposure to smoke, and other air pollution, as much as they can. The Hazelwood fire was a long duration event (45 days) so there was a long exposure for those that remained in the region (I would expect we will see similar results from epi studies from the 2019/2020 bushfires). The literature on bushfires and birth outcomes (eg LBW, SGA, gestation) is not consistent but often the exposures are of reasonably short duration. The main message is to reduce exposure any way they are able (stay indoors (unless house is full of smoke), go to clean air shelters, reduce outdoor activity, temporary relocation if fires are going to be prolonged, portable air filters (for short duration)). I think they need to know the options for reducing their exposure and deciding what they can do considering the disruption to their lives. As I mentioned in the talk there is a very good article in the MJA that discusses the smoke exposure reduction strategies and the strength of evidence for their effectiveness (generally very little evidence – more based on common sense) (ref: Vardoulakis et al. Bushfire smoke: urgent need for a national health protection strategy. MJA 2020; 212: 349)