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| Last Updated:09/10/2018

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Black carbon level in city 5 times higher than WHO limits: study (The Hindu,01/02/2017)

High vehicular emission levels have created pollution hotspots in city


The ambient black carbon (BC) concentration in the city has been found to be about five times higher than the limits set by the World Health Organisation (WHO).


It was found that the city had BC measurement of over 95,000 ng/m3 (nanogram per cubic metre) whereas the WHO mentions levels of BC not more than 20,000 ng/m3 to be safe. BC is a significant light absorbing particulate matter in the air formed by the burning of fuels.


The BC values were found by Biju Thomas, paediatric respiratory medicine consultant from Singapore, who undertook a study to find a person’s exposure to black carbon in Kochi.


According to Dr. Thomas, high vehicular emission levels at various traffic junctions had created hotspots of pollution in the city, especially at Edappally and Vyttila. The two junctions had shown higher levels of BC concentration compared to other congested areas such as Kaloor Junction, Kadavanthra Junction, Collectorate traffic signal and Medical Trust Junction and M.G. Road.


The study measured BC exposure inside the car cabin while driving along city roads. Measurements were taken during the morning rush hours (8 a.m. to 10 a.m.) on weekdays. Fifty hours of readings at each of the three in-cabin ventilation preferences — with windows open (WO), windows closed (WC) with outer air intake and windows closed with in-cabin air circulation (WCRO) — were taken, using a portable aethalometer.


The mean (standard error) ng/m3 in-cabin BC concentration with WO was 95,040 (1391), significantly higher compared to WC 23,838 (147.8) and WCRO 8,485 (80.3). The in-cabin BC concentration with WCRO ventilation option was 10 times lower compared to WO option. This was irrespective of the ambient air pollution level.


When windows are closed, switching the ‘re-circulate’ button on, allowing cabin air recirculation, may reduce the in-cabin BC exposure by at least two-third. The in-cabin BC concentration in cars may be brought down below the WHO limits by putting the windows up and switching on the ‘re-circulate’ button.


Impact on health


It has been found that nano particles of BC in the blood stream causes inflammation of various tissues depending on where they are lodged, said Dr. Thomas.


WHO had listed a range of health effects of BC including lung diseases, cancer, stroke and ischemic heart disease. Berkeley Health, a non-profit climate research organisation, had recently reported that air pollution was responsible for about 16 lakh deaths in China.


Spreading awareness


“Given that the air pollution levels are on the rise and there is no short term solution to the problem, it is important to raise awareness among the public so that they can try and deal with it in a better way,” said Dr. Thomas, who made a presentation of the study at Pedicon 2017, the national conference of Indian Academy of Paediatrics, held in Bengaluru from January 18 to 22. “The people can make informed choices so as to minimise personal BC exposure,” he said. An awareness of pollution hotspots would help guide the public in their choice of mode and route of travel, he added.


Simple measures such as avoiding rush hours for non-urgent travel, car sharing for work or shopping, servicing vehicles as per manufacturer’s guidelines and adherence to vehicle emission standards may be helpful.