Bushfire smoke increasing global public health concern

The number of people exposed to toxic smoke from bushfires around the world has alarmed scientists.

A study published today in Nature estimated global daily air pollution from all landscape fires from 2000 to 2019, finding:

• 2.18 billion people were exposed to at least 1 day of substantial landscape fire air pollution annually.
• Each person in the world had 9.9 days of exposure per year on average, an increase of 2.1% in the past decade.

It also found exposure levels in low-income countries were about four times higher than in high-income countries.

This comprehensive assessment of the global population’s exposure to fine particulate matter (PM2.5) and surface ozone concentrations from outdoor fires during 2000-2019 was calculated using a machine-learning approach with inputs from chemical transport models, ground-based monitoring stations, and weather data.

In the study, landscape fires refer to any burning in natural and cultural landscapes, including planned or controlled fires and wildfires. The authors report substantial fire-sourced air pollution increased significantly from 63.2 billion exposed person-days per year during the period 2000–2009 to 72.8 billion per year during 2010–2019.

Country	Person days/year
DR Congo	11.6 billion
Indonesia	7.2 billion
Brazil	4.9 billion
Angola	4.3 billion
Tanzania	4.1 billion

Country	People/year
Brazil	189.4 million
USA	165.1 million
Indonesia	154.7 million
China	139 million
Russia	97.5 million

The assessment was conducted by Professors Yuming Guo and Shanshan Li, from Monash University’s School of Population Health and Preventive Medicine. They found billions of people were exposed to substantial landscape fire-sourced air pollution, with particularly high exposure levels in several hotspots across Central Africa, Southeast Asia, South America and Siberia.

Australia, the United States and Canada were identified as hotspots for fire-sourced air pollution caused by catastrophic wildfire events.

“Fire-sourced air pollution can often travel hundreds (sometimes even thousands) of kilometres and affect much larger populations, causing greater health consequences,” says Guo.

Short-term exposure to fire-sourced air pollution has many adverse health impacts, including increased mortality and exacerbations of cardiorespiratory conditions.

The authors say the large quantity and increasing trend of the population exposure to substantial fire-sourced air pollution suggests that landscape fire air pollution is an increasing public health concern.

“Addressing this concern needs multisectoral efforts to reduce landscape fires and prevent adverse health impacts of landscape fire air pollution. Landscape fires can be partially reduced through effective evidence-based fire management, as well as appropriate planning and design of natural and urban landscapes,” they write.

They propose policy change to agricultural waste burning in northern hemisphere nations and deliberately set fires to convert land for agricultural or commercial use could reduce landscape fires.

“However, unplanned wildfires are more difficult to control, as evidenced by the fact that aggressive fire suppression actually contributed to the extreme wildfires in the western United States in recent decades because of fuel accumulation.”

“Because the increasing severity and frequency of wildfires are related to anthropogenic climate change, our finding about the socioeconomic disparities provides further evidence of climate injustice, that is, those least responsible for climate change suffer the most from its consequences.”