Ammonium Nitrate Chemistry

Air Pollution Hangs Over Sydney

A blanket of smoke covered Sydney earlier this week, raising some complex questions about how we balance public health and safety when it comes to air pollution.

Hazardous air quality levels were recorded across Sydney on Tuesday, with more than 60 people reported to require treatment for acute respiratory issues.  There was some exaggerated reporting about air pollution in Sydney being worse than Beijing - which is actually not shocking given that it is summer in the northern hemisphere and a same-day comparison is almost meaningless - but nevertheless, the recorded air quality index (AQI) values in excess of 200 (even above 400 in some locations) were dangerous, especially to vulnerable groups such as children, the elderly, and those with known respiratory issues.

The culprit in this latest pollution event was planned and controlled fuel reduction burns, which themselves are an unavoidable part of living safely alongside the Australian bush.  Unfortunately, the best conditions for controlled burns - cold, still days - can result in the greatest air pollution threats, with smoldering fires and trapped smoke plumes.  It will be difficult to decide just how much importance we should place on air pollution risks when managing bush fires, but severe impacts on the air that millions of people breathe must be taken into consideration.  We do have the capacity to model the extent of air pollution from controlled burns beforehand, based on meteorological predictions, and this needs to be incorporated into planned burns if it isn't already, with the results used to inform when to carry out burns and to alert the public of their potential severity.  There are also worrying reports that logging burns in Victorian forests are being described as fuel reduction efforts, and it is difficult to see these as being in the public interest.

A broader issue here is that the bush fire season in Australia has been moving earlier and earlier in the year, and it will continue to do so on our warming planet.  The need to co-exist with fires and air pollution is here to stay, and we need to think seriously about how to best manage this.