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Air pollution: Identifying the reasons behind declining AQI

Towhid Iqram Mahmood | February 14, 2019 00:00:00

Most of Dhaka city's citizens are regularly troubled by the deteriorating air quality around the city through illnesses and pollution. A "megacity" by definition, Dhaka fails to provide its inhabitants with proper air quality. Other major cities in Bangladesh are not lagging far behind Dhaka in terms of air pollution. As data on Air Quality Index (AQI) from the Ministry of Environment and Forests show, average air quality has been deteriorating gradually in all the cities over the past six years.

AQI is used by government agencies to inform the public about how polluted the air currently is or how polluted it will become as indicated by forecasts. As the AQI increases, an increasingly large percentage of the population is likely to experience increasingly severe and adverse health effects. Based on daily data, in 2015 the average AQI in the country was less than 100 whereas in 2018 it increased to close to 150.

Data show that cities with large concentration of heavy factories are facing increasing pollution. For example, average AQI for Dhaka, Narayanganj and Gazipur are relatively higher than the rest of the country from where AQI data has been collected. If we consider this analogy of pollution due to industrial production, then the weekends should be less polluted i.e. the AQI should be lower on those days. However, an analysis of daily data has reflected that for Gazipur and Narayanganj, this is not the case. The average AQI for these three cities are around or above 150 which by definition is "Unhealthy for Sensitive Groups".

Going back to the discussion of AQI each day, for Dhaka city no major differences are found in AQI for Fridays, Saturdays, and Sundays. Highest AQI is mostly experienced on Tuesdays. The proximity between average daily AQI is very low and mostly stays above 150, which is "Unhealthy" by definition.

For Gazipur, average AQI is relatively lower than nearby cities. However, it still stays in the "Unhealthy for Sensitive Groups" level. Interestingly, average lowest AQI levels were recorded on Wednesdays and Thursdays. For Fridays and Saturdays, the average AQI is greater than that of Mondays, Wednesdays and Thursdays. The proximity of daily measure is very low for Gazipur as well, indicating functioning of pollutants even on weekends.

Most unhealthy of all the cities is Narayanganj. Average daily AQI for Narayanganj over the last four years was 168. For Narayanganj, though Fridays see relatively lower level of AQI, Saturdays have higher AQI than most of the days in a week.

Even on weekends these industry-heavy cities see higher levels of AQI. One explanation for this could be higher load of traffic on the road on weekends. Perhaps that is just a part of it. To understand the impact of traffic on AQI level, the number of vehicles moving through the cities on weekends can be recorded. If we closely look at average AQI for each day, there is not much day-to-day variation for any of the cities. One explanation for this could be unregulated industrial production and construction works on weekends. For the government, it is very important to control air pollution as soon as possible to maintain a better environment for future and to reach the Sustainable Development Goals (SDG).

Recently, the High Court has ordered Department of Environment to conduct mobile court drives twice a week against parties causing air pollution in the capital. Similar actions should be considered for other industrial zones and industry-heavy cities across the country.

Towhid Iqram Mahmood is a research economist at South Asian Network on Economic

Modelling (SANEM)

[email protected]

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