Washington: Smoke particles produced from burning roadside trash piles in India are 1,000 times more toxic to humans standing nearby than ambient air, a new study has found.
Of the nearly two billion tonnes of garbage produced worldwide each year, nearly half of it is burned for disposal, according to some estimates.
While much of this total is burned in large collection and disposal sites away from heavily populated areas, many cities and towns do not have the infrastructure in place to collect waste - especially in India.
"As you walk down the street in India, there are just piles of trash growing larger and larger until somebody decides to take a match to it," said lead author Heidi Vreeland, doctoral student at Duke University in the US.
"Even in large cities such as Bangalore, and even in the more affluent neighbourhoods, this is just the norm," said Vreeland.
"From our tests, we found that somebody standing near one of these fires is getting a dose of toxins 1,000 times greater than they would from the ambient air," said Michael Bergin, professor from Duke.
"To put it another way, a person would only need to breathe these particles for a minute to get an entire day's worth of hazardous particulate matter," said Bergin.
Researchers took samples of emissions coming from 24 roadside garbage fires in urban Bangalore. They then tested the collected particles for toxicity through both a chemical analysis and by applying them to cultured cells.
While the results showing that the high concentrations of particles near the fires resulted in 1,000 times more toxic exposures to nearby humans, one aspect of the experiment was eye-raising.
Thanks to various organic compounds burning in each fire, the test filters were turned into different colours, making a rainbow of toxins.
"When you take samples of ambient air either here in the US or in India, you just get different shades of grey," said Vreeland.
"But these smoldering fires turned our filters such different colours that one of my lab-mates actually thought I was looking at a panel of eye shadows," she said.
The wide variability found in the fumes likely stems from the trash piles containing many different organic and plastic materials.
It is also a result of smoldering, incomplete combustion, which offers at least one insight into how the practice might be improved.
"Just making sure the fire is hot enough and there's enough material available could go a long way to reducing its toxicity," said Bergin, who is beginning work on systems and recommendations that could help such roadside fires be less toxic, and perhaps even to recoup some energy from their burning.
The findings were published in the journal Atmospheric Environment.