What did the study reveal about the link between smoke exposure and mortality?
The component of smoke most damaging to health is fine particulate matter (PM2.5 ) – which can penetrate deep into the lung and then go on to damage in other parts of the body. The new research, published in Lancet Planetary Health, examined hundreds of thousands of child deaths in 55 low-income and middle-income countries (LMICs).
The first component of the work focused on developing a relationship between child mortality and the amount of PM2.5 the children were exposed to as a result of landscape burning. This so-called “exposure response function” is one of the first ever developed specifically for landscape fire effects on children.
The second component combined this new information with worldwide population information and global airborne PM2.5 concentration data taken from a combination of satellite data and air quality modelling - focusing only on the PM2.5 coming from landscape fires not that from other sources such as vehicles and industry.
Using this, the researchers calculated that over 9% of deaths in children under five worldwide are driven by inhaling smoke from landscape fires (2000-2014 period). Considering other causes of mortality such as malnutrition, poor sanitation, and diseases such as malaria, this seems a huge percentage – equating to between 760 and 960 thousand deaths per year. Almost all these deaths are in low- and middle-income countries, and in some nations more than 30% of child deaths in the under-fives were from this source.
Which parts of the world are affected by this?
The countries with the highest child mortality figures linked to landscape fire smoke inhalation were Nigeria and the Democratic Republic of Congo – with over 100 thousand deaths estimated annually on both nations, along with India, Uganda, and Indonesia each with around 30 to 60 thousand. In some of these countries, airborne PM2.5 concentrations can reach really extreme levels during the burning season. In parts of Indonesia for example, our group has previously measured levels well over 1000 micrograms per cubmic metre of air, far in excess of the World Health Organisation’s top limit of 300 micrograms per cubic metre of air, which they class as ‘extremely hazardous to health’.
What do you hope will result from the research?
Overall, it is hoped that this research will help intergovernmental organisations such as WMO, child health services, NGO’s and others to recommend and ultimately help implement interventions to protect children’s health by lowering the prevalence of recurrent landscape fires in many parts of the world – which are related for example to the removal of rice straw and wheat stubble after harvest.
How does the study change our understanding of this global problem?
Contrary to perhaps popular understanding, the majority of health impacts from landscape fires are related to human-driven fires used routinely for land management, primarily those related to deforestation and peatland burning, and agricultural burning of straw and stubble – rather than so-called ‘wildfires’. The health impacts from all these fires mainly come from the air pollution they generate, rather than the fires themselves.