Recent spatial gradients and time trends in Dhaka, Bangladesh, air pollution and their human health implications

Abstract

Dhaka, the capital of Bangladesh, is among the most polluted cities in the world. This research evaluates seasonal patterns, day-of-week patterns, spatial gradients, and trends in PM 2.5 (<2.5 µm in aerodynamic diameter), PM 10 (<10 µm in aerodynamic diameter), and gaseous pollutants concentrations (SO 2 , NO 2 , CO, and O 3) monitored in Dhaka from 2013 to 2017. It expands on past work by considering multiple monitoring sites and air pollutants. Except for ozone, the average concentrations of these pollutants showed strong seasonal variation, with maximum during winter and minimum during monsoon, with the pollution concentration of PM 2.5 and PM 10 being roughly five-to sixfold higher during winter versus monsoon. Our comparisons of the pollutant concentrations with Bangladesh NAAQS and U.S. NAAQS limits analysis indicate particulate matter (PM 2.5 and PM 10) as the air pollutants of greatest concern, as they frequently exceeded the Bangladesh NAAQS and U.S. NAAQS, especially during nonmonsoon time. In contrast, gaseous pollutants reported far fewer exceedances throughout the study period. During the study period, the highest number of exceedances of NAAQS limits in Dhaka City (Darus-Salam site) were found for PM 2.5 (72% of total study days), followed by PM 10 (40% of total study days), O 3 (1.7% of total study days), SO 2 (0.38% of total study days), and CO (0.25% of total study days). The trend analyses results showed statistically significant positive slopes over time for SO 2 (5.6 ppb yr −1 , 95% confidence interval [CI]: 0.7, 10.5) and CO (0.32 ppm yr −1 , 95% CI: 0.01, 0.56), which suggest increase in brick kilns operation and high-sulfur diesel use. Though statistically nonsignificant annual decreasing slopes for PM 2.5 (−4.6 µg/m 3 yr −1 , 95% CI: −12.7, 3.6) and PM 10 (−2.7 µg/m 3 yr −1 , 95% CI: −7.9, 2.5) were observed during this study period, the PM 2.5 concentration is still too high (~82.0 µg/m 3) and can cause severe impact on human health. Implications: This study revealed key insights into air quality challenges across Dhaka, Bangladesh, indicating particulate matter (PM) as Dhaka's most serious air pollutant threat to human health. The results of these analyses indicate that there is a need for immediate further investigations, and action based on those investigations, including the conduct local epidemiological PM exposure-human health effects studies for this city, in order to determine the most public health effective interventions.

Investigating PM2.5 responses to other air pollutants and meteorological factors across multiple temporal scales

“…The influence of PM 2.5 daily oscillation (IMF1 ~ 4) on the overall variation of PM 2.5 is 49.61%, while the monthly oscillation (IMF5 ~ 9, RES) is 50.39%, and the contribution of monthly oscillation is slightly higher than that of daily oscillation. Therefore, the daily and monthly scales are two important temporal scales in the PM 2.5 time series in Nanjing, which is consistent with the temporal of PM 2.5 that found in other studies as daily, monthly, and annual 22 .…”

A Meteorology Based Particulate Matter Prediction Model for Megacity Dhaka

“…Dhaka is ranked as the third most polluted megacities (Rahman et al, 2019) and the second most polluted capital in terms of poor air quality (IQAir, 2018). The huge population of the city (~9 million) is constantly exposed to a high concentration of PM2.5 and PM10 (particles with an aerodynamic diameter less than 10 µm) for many years (Begum et al, 2013 and;Majumder et al, 2019).…”

“…PM shows a strong positive association with all-cause mortality (Choi et al, 2009), respiratory morbidity, and possibly cardiovascular mortality and morbidity (Thurston et al, 2016). PM2.5 (particles with an aerodynamic diameter less than 2.5 µm) is also a big concern in ambient air in Bangladesh as evidenced by various observations spanning over several decades (Rahman et al, 2019). Observations since 1990 show that the population of this country has been exposed to PM2.5 levels above all three interim targets of the World Health Organization (WHO), making it one the countries with the highest PM2.5 exposures (Health Effects Institute, 2019).…”

“…Thus, ambient PM2.5 has become one of the top risk factors affecting cardiovascular morbidity and mortality in Bangladesh (Islam et al, 2017). Each year, air pollution causes 195,000 premature death here (Rahman et al, 2019). PM2.5 attributed annual mortality in Bangladesh is also increasing over time and has been increased by 52% in the last two decades (Health Effect Institute, 2017).…”

Estimation of particulate matter (PM2.5, PM10) concentration and its variation over urban sites in Bangladesh

“…A detailed study by [33] found recursively high annual mean concentrations of PM 10 ( > 150 μg m −3 ) over Dhaka, Gazipur and Narayanganj during 2012-2015. Annual mean concentration of 80-100 μg m −3 for PM 2.5 and 140-200 μg m −3 for PM 10 was recorded during 2013-2017 over Darus Salam, Narayanganj and Gazipur [34]. Therefore, all of these major studies propound an importance of regular monitoring of PM over larger regional extent which can only be possible using satellite data, because with the ground network only point level or local scale information can be acquired which does not need to be the same over regional extent [35].…”