The air in the city is carrying more than just a whiff of noxious greenhouse gasses. Dangerous heavy metals seem to be accompanying the usual suspects of carbon dioxide and nitrous oxides.
Studying this accumulation on feathers, fur and even human hair across the city, researchers and students of Vijaya College found that at least seven heavy metals, most of them toxic, are being absorbed from the air.
The analysis shows that hens carry nearly seven heavy metals on their feathers; while crows, arguably the most common bird in the city, carried at least five including cadmium, iron, zinc and nickel. Metals were found in sheep, goats, cats and dogs, some even carrying molybdenum. The tests conducted on human hair show the presence of at least six heavy metals, including the presence of mercury on women’s hair.
“We wanted to show that these samples can serve as bio-indicators for the assessment of heavy metal pollution in the environment. Not all pollutants may have come from the air, but it is definitely something that should be researched further,” said Priyadarshini P.A., professor of Genetics, Vijaya College, who is the lead author of the study. The effects of these metals in large amounts in the air range from higher risks of allergies to adverse effects on metabolism owing to long exposure, and even the absorption of such metals into the blood stream.
The local study adds to the growing research of heavy metals pollution, arising largely from automobile exhausts and industries.
In 2017, a research paper by Bapuji Institute of Engineering and Technology in Davangere looked at the presence of arsenic, cadmium and lead in the air in residential and industrial areas in Rajajinagar. Predictably, industrial areas in the region showed higher concentrations of arsenic (which is often a gaseous by-product of industries).
Similarly, the amount of lead and cadmium (as a result of battery production or disposal) was also higher in industrial areas.
Much of the city’s focus is on greenhouse gases that lead to warming or visible pollution, rather than heavy metals. The Karnataka State Pollution Control Board only tabulates the lead content in the air. “Heavy metal pollution is a big concern, not just in Bengaluru but other cities too,” a senior KSPCB officer said.
Their research into 42 heavy metals present in the dust in Bengaluru showed a major spike. While the lead level is below national standards, the air in Bengaluru has five times the lead content as compared to other cities in the State. “There are 78 lakh vehicles and each car can spew out up to 22 metals, either through the exhaust or as wear and tear,” explained the officer.
Air pollution lessens
It may be hard to believe, but the city’s air may have become a little cleaner. The Karnataka State Pollution Control Board (KSPCB)’s analysis of air pollution for 2017-18 shows a significant dip in particulate matter pollution from the previous years.
For the previous financial year, the average particulate matter 10 (that is, fine dust of 10 microns) was 87.1 microgrammes per cubic meter, nearly 45% above the 60 umg/m3 limit set. However, this is a reduction of around 17% from the 106 microgrammes per cubic meter recorded in 2016-17, and the staggering 117 microgrammes per cubic meter recorded in 2015-16.
Multiple reasons
Officials attribute multiple reasons for the decrease: completion of metro construction which reduced debris; better cleaning of roads; asphalting of roads and creation of one-ways to smoothen traffic flows.
Adding to this is the record rainfall in the previous year, which saw pollution levels drastically drop for months. “There is a declining trend in PM10 levels has been observed for a few years, and much of it after coordination committees were formed following the High Court order. The functioning of the metro has helped too,” said an officer.
However, pollutants emitting from vehicles are on the rise. PM2.5, which is fine dust particle emitted from vehicles, has gone up to 43.1 microgrammes per cubic meter, up from 36.24 in 2016-17, and 37.82 in 2015-16. Similarly, nitrous oxides, sulphur oxides and lead are on the rise in the air.
