• There is an urgent need to address the alarming levels of air pollution in Kathmandu

Sep 11, 2015-

Air pollution has always been a serious problem in Kathmandu Valley. And now, new evidences suggest that it is increasing. The air in Kathmandu is so polluted that the levels of particulate pollution—commonly measured as PM10 (total mass of particles smaller than 10 micrometer)—are within the safe limit, mentioned in Nepal’s own daily ambient air quality standards, only for one month in a year. Most times, the three and a half million residents of the Capital are thus exposed to the hazardous levels of dhulo ra dhuwa.

Alarmingly polluted

The small particles in the Valley are made of several chemical constituents, with alarmingly high concentrations of very toxic and cancer causing chemicals, says a new study, ‘Characteristics and sources of polycyclic aromatic hydrocarbons in atmospheric aerosols in the Kathmandu Valley, Nepal’, published in the journal Science of the Total Environment last month. The article was written by a group of scientists from the Chinese Academy of Sciences, China; the Institute for Advanced Sustainability Studies, Germany and the Lappeenranta University of Technology, Finland. The study reports that 15 priority polycyclic aromatic hydrocarbons (PAHs)—defined as priority PAHs by the World Health Organisation (WHO) and the United States Environmental Protection Agency—were found in ambient particles collected at Bode, Bhaktapur from April 2013-March 2014. PAHs are a group of organic compounds that are formed due to the incomplete combustion of fuels such as coal, wood, petroleum products, and garbage. According to the WHO, many of these compounds are highly carcinogenic (cancer causing) to humans even at relatively low levels.

The study reported very high levels of PAHs at Bode. The average concentration of the total PAHs at Bode was 155 nanogram per cubic meter, which is comparable to that observed in Beijing (160 nanogram per cubic meter) and higher than the levels observed in Delhi (105 nanogram per cubic meter), two major and highly polluted megacities in Asia. Toxic equivalent quantity (TEQ), an indicator for the health-risk (toxicity) of a mixture of PAHs, varied from between two and 80 nanogram TEQ per cubic meter each day, which is shockingly higher than the national standard of China (10 nanogram TEQ per cubic meter and the WHO’s guideline (one nanogram TEQ per cubic meter). In fact, the TEQ never dropped below one nanogram in Bode throughout the year. Further, the PAH concentrations were observed to be extremely high during winter months, four to six times higher than during the summer and monsoon.

In addition, the study has found out that diesel and biomass fuel combustion are the main sources of PAHs. This is not quite surprising, given that the Valley has nearly 700,000 motor vehicles, almost a half of the total vehicle fleet in the country, with engines of Euro II or lower emission standards. There are over 110 brick factories around the Capital, which burn wood and low-grade coal imported from India with old technologies, and pollute the Valley’s air with dirty smoke.

Over 250,000 small power generators, mostly powered by diesel, are used in the Valley to cope with the load-shedding of upto 18 hours a day, according to a study by the World Bank last year. During winter months, an increase in wood and coal combustion in brick factories; use of small power generators in large numbers; increase in the use of firewood and petroleum products for cooking and heating the houses; and the  rampant burning of garbage and agriculture residue emit high amount of PAHs and other air pollutants. While in the summer, they mostly come from traffic emissions. However, it is not just emissions, but also the bowl-shaped structure of the Valley and the local meteorological conditions that result in  the poor dispersion of air pollutants. Furthermore, what happens outside the Valley also has an impact. For example, the smoke of forest fires from the surrounding regions of Kathmandu also brings in additional PAHs into the Valley in the pre-monsoon season.

 Kathmandu’s air is clearly a mixture of toxic air pollutants, including PAHs. As the air pollutants pose a serious health risk to its 3.5 million residents, there is an urgent need for concerted efforts to address air pollution in the Capital. This deserves an immediate attention of the concerned government authorities, industrialists and associations, non-government organisations, and also from the general public, to steer the current policies and practices towards cleaner solutions which are equipped with strategies and action plans that are deeply rooted in sound science and the local context. Otherwise, experiences from around the world, have shown that inaction or delaying steps to cut down air pollution could prove to be very expensive in the future.  

Chaulagain is an intern at The Kathmandu Post

Published: 11-09-2015 08:29

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