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<p>Black carbon (BC) is a critical component of fine particulate matter (PM<sub>2.5</sub>) and plays a dual role in climate forcing and adverse human health outcomes. Despite the presence of substantial BC emission sources in South Asian megacities, including vehicular traffic and industrial activities, limited data are available for Pakistan. This study quantified real-time BC concentrations at residential and commercial locations in Karachi using MicroAeth® AE51 monitors during peak and off-peak traffic hours. The highest BC concentration was recorded at Karachi Cantonment (10.6&#xa0;µg/m<sup>3</sup>), followed by Gulshan-e-Iqbal Block-7 (6.79&#xa0;µg/m<sup>3</sup>) and Mosamiyat (5.46&#xa0;µg/m<sup>3</sup>), whereas the lowest levels were observed at the University of Karachi (3.58&#xa0;µg/m<sup>3</sup>) and Malir (2.54&#xa0;µg/m<sup>3</sup>). Diesel-powered vehicular emissions were identified as the dominant source influencing most sites. Correlation analysis indicated that BC variability was strongly associated with anthropogenic activities and meteorological parameters. Health risk assessment revealed lifetime cancer risks of 1.22 × 10<sup>−3</sup> for children and 2.99 × 10<sup>−3</sup> for adults, exceeding the acceptable risk range recommended by the U.S. Environmental Protection Agency (US EPA). However, non-carcinogenic hazard quotient (HQ) values remained below unity, suggesting negligible non-cancer risk. These findings highlight the urgent need for targeted mitigation strategies to reduce BC exposure in Karachi.</p> Graphical abstract <p></p>

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Spatiotemporal variability and health risk assessment of black carbon in a megacity of Karachi, Pakistan

  • 期刊论文

  • 发表日期：

    2026年6月18日

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  • J. Javed,
  • E. Zahir,
  • M. K. Khan,
  • A. Fazal,
  • H. A. Khwaja

摘要

Black carbon (BC) is a critical component of fine particulate matter (PM2.5) and plays a dual role in climate forcing and adverse human health outcomes. Despite the presence of substantial BC emission sources in South Asian megacities, including vehicular traffic and industrial activities, limited data are available for Pakistan. This study quantified real-time BC concentrations at residential and commercial locations in Karachi using MicroAeth® AE51 monitors during peak and off-peak traffic hours. The highest BC concentration was recorded at Karachi Cantonment (10.6 µg/m3), followed by Gulshan-e-Iqbal Block-7 (6.79 µg/m3) and Mosamiyat (5.46 µg/m3), whereas the lowest levels were observed at the University of Karachi (3.58 µg/m3) and Malir (2.54 µg/m3). Diesel-powered vehicular emissions were identified as the dominant source influencing most sites. Correlation analysis indicated that BC variability was strongly associated with anthropogenic activities and meteorological parameters. Health risk assessment revealed lifetime cancer risks of 1.22 × 10−3 for children and 2.99 × 10−3 for adults, exceeding the acceptable risk range recommended by the U.S. Environmental Protection Agency (US EPA). However, non-carcinogenic hazard quotient (HQ) values remained below unity, suggesting negligible non-cancer risk. These findings highlight the urgent need for targeted mitigation strategies to reduce BC exposure in Karachi.

Graphical abstract