According to the World Health Organization (WHO), ambient air pollution was the cause of 3.7 million premature deaths in 2012. Numerous studies have linked airborne particulate matter to a variety of health consequences, including premature death in people with existing lung and cardiac disease, nonfatal heart attacks, aggravated asthma, irregular heartbeat, decreased lung function and general respiratory problems.
Previous research has also shown that smaller particulate matter, under 2.5 µm in diameter (PM2.5), is significantly worse for health than larger particles of 10 µm in diameter or more. This difference is due to a smaller particle's ability to enter deeper into the lungs and successfully maneuver within the blood system. Containing substances such as arsenic, mercury and selenium, once inside the human body, they are free to wreak havoc.
Exposure to PM2.5 particles over just a few hours or weeks can trigger cardiovascular disease-related mortality and other negative health events. Longer exposure times - a year or more - increases the likelihood of cardiovascular mortality even further. A new, first of its kind, study split pollution by type, as well as size; rather than simply looking at the diameter of particles, the researchers investigated the source of the pollution, for instance, coal burning, traffic fumes or wood burning.
Delving into the records of 45,000 patients between 1982 and 2004 the research team estimated the size, type and amount of pollution each individual would have encountered and then using trace element ‘fingerprints’, estimated the contributions from each of the types of PM2.5. They found that coal-burning contains traces of selenium and arsenic;; traffic emissions contain elemental carbon and oil combustion contains vanadium and nickel. Soil particles were shown to contain calcium and silicon, while wood-burning particles showed traces of potassium.
As expected, the results underlined that inhaling coal pollution was bad for health; but it was the strength of the result that surprised researchers. Past studies of this kind had assumed that all PM2.5 particles have the same toxicity, irrespective of their source. But researchers found that kilogram-for-kilogram the particles from coal-burning were five times worse than other particle types of the same size.
They also found that particles from burning fossil fuels were associated with an increased risk of death from ischemic heart disease. Interestingly, the team found that PM2.5 from wind-blown soil and the burning of biomass, like wood, were "non-significant contributors" to mortality risk.
The study's authors recommend that, on the basis of these findings, the main thrust of air pollution control should focus specifically on coal burning.