Air pollution we breathe: Assessing the air quality and human health impact in a megacity of Southeast Asia

• Published in: The Science of the total environment Vol. 942; p. 173403
• Main Authors: Sannoh, Fatim, Fatmi, Zafar, Carpenter, David O., Santoso, Muhayatun, Siddique, Azhar, Khan, Kamran, Zeb, Jahan, Hussain, Mirza M., Khwaja, Haider A.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 10.09.2024
• Subjects: Fine particle chemical composition; Health risk assessment; Source identification; Southeast Asia; Urban pollution; Southeast Asia; Urban pollution; Source identification; Health risk assessment; Fine particle chemical composition
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2024.173403

With 24 million inhabitants and 6.6 million vehicles on the roads, Karachi, Pakistan ranks among the world's most polluted cities due to high levels of fine particulate matter (PM2.5). This study aims to investigate PM2.5 mass, seasonal and temporal variability, chemical characterization, source apportionment, and health risk assessment at two urban sites in Karachi. Samples were analyzed using ion chromatography and dual-wavelength optical transmissometer for various inorganic components (anions, cations, and trace elements) and black carbon (BC). Several PM2.5 pollution episodes were frequently observed, with annual mean concentrations at Kemari (140 ± 179 μg/m3) and Malir (95 ± 40.9 μg/m3) being significantly above the World Health Organization's guidelines of 5 μg/m3. Chemical composition at both sites exhibited seasonal variability, with higher pollution levels in winter and fall and lower concentrations in summer. The annual average BC concentrations were 4.86 ± 5.29 μg/m3 and 4.52 ± 3.68 μg/m3, respectively. A Positive Matrix Factorization (PMF) analysis identified 5 factors, crustal, sea salt, vehicular exhaust, fossil-fuel combustion, and industrial emission. The health risk assessment indicated a higher number of deaths in colder seasons (fall and winter) at the Kemari (328,794 and 287,814) and Malir (228,406 and 165,737) sites and potential non-carcinogenic and carcinogenic risks to children from metals. The non-carcinogenic risk of PM2.5 bound Pb, Fe, Zn, Mn, Cr, Cu and Ni via inhalation exposure were within the acceptable level (<1) for adults. However, potential non-carcinogenic and carcinogenic health risk posed by Pb and Cr through inhalation were observed for children. The findings exhibit critical levels of air pollution that exceed the safe limits in Karachi, posing significant health risks to children and sensitive groups. Our study underscores the urgent need for effective emission control strategies and policy interventions to mitigate these air pollution risks. [Display omitted] •Concentrations of PM2.5 constituents determined in Karachi and PMF was used for source apportionment.•BC, SO42-, NO3-, and trace metals were the most abundant contaminants in PM2.5.•5 identified factors were crustal, sea salt, vehicular emissions, oil combustion, and industrial emissions.•Health risk from metals in PM2.5 is estimated.•Air quality in Karachi is extremely poor and poses a risk to human health.