Rampant burning of rubbish is throwing more pollution and toxic particles into the air than governments are reporting, according to a scientific study estimating more than 40 per cent of the world's refuse is burned.
The study, published in the journal Environmental Science and Technology, attempts the first comprehensive assessment of global refuse-burning data, including how much carbon dioxide, carbon monoxide, mercury and tiny particulate matter that can dim the sun's rays or clog human lungs is produced.
It includes the first country-by-country index of rough emissions estimates for both carbon dioxide and toxic pollutants linked to human disease, although researchers acknowledge the index is a "first draft" based on estimates and some measures could be off by 20-50 per cent.
"There is a lot of room for improvement in the index," leader researcher Christine Wiedinmyer said, but expressed hope it would still help policymakers set agendas to clear the air. "Most health regulations are based on the total mass of particles in the air, based on their size. But that's not getting at what the particles are made of. That can have different health impacts as well as different impacts on the climate."
While many governments tally emissions from incinerators, the burning of rubbish in backyards, fields and dumps is mostly unregulated and unreported.
Researchers pulled together existing data on population, per capita production of refuse and official reports on waste disposal to calculate how much rubbish is burned around the world each year. The answer: 41 per cent of our global two billion tonne annual output goes up in flames.
China and India were found to have the most rubbish burned by residents, while China, Brazil and Mexico burned the most at rubbish dumps.
Much of the world's air pollution can be blamed on burning refuse, including discarded plastics, electronic devices, furniture and food scraps.
According to the study, 29 per cent of the finest airborne particles, known as PM2.5, which can penetrate deep into the lungs, comes from such fires, as well as 10 per cent of toxic mercury emissions. China's emissions, for example, are not reflected in official data for the slightly larger PM10 particles; the study shows those emissions are equal to 20 per cent of what's reported.
The study also showed that globally, rubbish burning releases about 5 per cent of man-made emissions of carbon dioxide, a potent greenhouse gas.