A New Model Suggests a Higher Burden of Death Due to Particulate Air Pollution

Particulate air pollution is generally agreed upon to be harmful to long-term health, particularly from sources prevalent in poorer regions of the world such as the smoke from wood fires used for cooking. Exposure to these airborne particles raises the burden of chronic inflammation, thus accelerating the onset and progression of all of the common age-related diseases, including cardiovascular disease and dementia, and increasing age-related mortality. The mechanism is fairly cut and dried, but the size of the effect on mortality is up for debate, as is often the case. Just how many deaths does it cause?

In today's research materials, researchers report on the outcome of using updated models of mortality risk due to particular exposure. They argue that the data of recent years shows that low doses of particulates are worse than thought, while the increasingly negative effects at high doses do not plateau as early as thought. Applying this to the model gives a much greater impact of particulate air pollution on human mortality than previously though. This is nonetheless a model, in which the many different connecting parts can be adjusted one way or another based on underlying arguments for the right or wrong way to do it. This paper is one position in an ongoing debate of many positions on the topic. It is not a great plan to sit in front of a wood fire every day, but it remains hard to pin down just how bad this is.

Pollution from fossil fuel combustion deadlier than previously thought

A new study found that fine particulate pollution generated by the burning of fossil fuels was responsible for one in five early deaths worldwide in 2018-far more than previously thought. The people most at risk are those "who can least afford it." The study found that, worldwide, 8 million premature deaths were linked to pollution from fossil fuel combustion, with 350,000 in the U.S. alone. Fine particulate pollution has been linked with health problems including lung cancer, heart attacks, asthma, and dementia, as well as higher death rates from COVID-19.

Global mortality from outdoor fine particle pollution generated by fossil fuel combustion: Results from GEOS-Chem

The burning of fossil fuels - especially coal, petrol, and diesel - is a major source of airborne fine particulate matter (PM2.5), and a key contributor to the global burden of mortality and disease. Previous risk assessments have examined the health response to total PM2.5, not just PM2.5 from fossil fuel combustion, and have used a concentration-response function with limited support from the literature and data at both high and low concentrations.

This assessment examines mortality associated with PM2.5 from only fossil fuel combustion, making use of a recent meta-analysis of newer studies with a wider range of exposure. We also estimated mortality due to lower respiratory infections (LRI) among children under the age of five in the Americas and Europe, regions for which we have reliable data on the relative risk of this health outcome from PM2.5 exposure.

We used the chemical transport model GEOS-Chem to estimate global exposure levels to fossil-fuel related PM2.5 in 2012. Relative risks of mortality were modeled using functions that link long-term exposure to PM2.5 and mortality, incorporating nonlinearity in the concentration response. We estimate a global total of 10.2 million premature deaths annually attributable to the fossil-fuel component of PM2.5. The greatest mortality impact is estimated over regions with substantial fossil fuel related PM2.5, notably China (3.9 million), India (2.5 million) and parts of eastern US, Europe and Southeast Asia.The estimate for China predates substantial decline in fossil fuel emissions and decreases to 2.4 million premature deaths due to 43.7% reduction in fossil fuel PM2.5 from 2012 to 2018 bringing the global total to 8.7 million premature deaths.

This study demonstrates that the fossil fuel component of PM2.5 contributes a large mortality burden. The steeper concentration-response function slope at lower concentrations leads to larger estimates than previously found in Europe and North America, and the slower drop-off in slope at higher concentrations results in larger estimates in Asia.