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<p>Airborne polycyclic aromatic hydrocarbons (PAHs) associated with particulate matter (PM) are recognized contributors to carcinogenic and oxidative health risks in urban environments, yet their size-resolved distribution and redox activity remain insufficiently characterized in megacities. This study presents an integrated observational assessment of 16 priority PAHs in PM₁₀, PM₂.₅, and PM₁ collected at an urban rooftop site in Delhi, India, during a winter early summer campaign (January–June 2024). Chemical speciation was combined with dithiothreitol (DTT) based oxidative potential measurements, molecular diagnostic ratios, Positive Matrix Factorization (PMF), and scanning electron microscopy energy dispersive X-ray spectroscopy (SEM–EDX) to examine size-dependent composition, source patterns, and health-relevant indicators. Total PAH concentrations exhibited pronounced temporal variability, with winter maxima (PM₁₀: 496 ± 36&#xa0;ng/m<sup>3</sup>; PM₂.₅: 312 ± 19&#xa0;ng/m<sup>3</sup>; PM₁: 212 ± 23&#xa0;ng/m<sup>3</sup>), consistent with enhanced combustion emissions and reduced atmospheric dispersion. While PM₁₀ contained the highest total PAH mass, high-molecular-weight (5–6 ring) carcinogenic PAHs were preferentially enriched in PM₂.₅ and PM₁. The ultra fine particle fractions showed enhanced mass-normalized oxidative potential (OPm), with wintertime mean values reaching ~ 0.5&#xa0;nmol/min/µg, indicating a greater capacity to induce oxidative stress per unit particle mass. PMF analysis identified traffic-related emissions, biomass burning, coal combustion, waste/plastic burning, and an aged/secondary combustion factor, although source mixing and atmospheric processing were evident. SEM–EDX observations revealed soot-like agglomerates with associated sulfur (S), potassium(K), and chlorine (Cl) signals, supporting mixed combustion influences. Screening-level health risk assessment using a U.S. EPA based inhalation model indicated that wintertime incremental lifetime cancer risk (ILCR) associated with PM₂.₅ and PM₁-bound PAHs approached or exceeded ~ 10⁻<sup>4</sup>, surpassing commonly applied acceptable risk thresholds and indicating a potential carcinogenic risk, particularly for adults. PM₁ accounted for a substantial fraction of PM₂.₅-associated cancer risk, underscoring the health relevance of ultrafine PAH-bearing particles. A composite particulate health risk index (PHRI) further suggested elevated potential risk for outdoor workers and socioeconomically vulnerable population groups. Overall, the findings highlight the disproportionate toxicological importance of fine and ultrafine PM-bound PAHs in Delhi and emphasize the need to target combustion-related sources to mitigate health-relevant exposures in megacity atmospheres.</p>

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Health risks and oxidative toxicity of size-resolved PAHs in fine and ultrafine particles from a megacity atmosphere

  • 期刊论文

  • 发表日期：

    2026年4月2日

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  • Molla Nageswar Rao,
  • Atar Singh Pipal,
  • Rakesh P.S,
  • Midhun M. Nair,
  • Arkabanee Mukherjee,
  • Akash S. Vispute,
  • Hardeep Sharma,
  • Pankaj Sharma,
  • Sandip S. Nivdange,
  • Chaitri Roy,
  • Abhilash S. Panicker,
  • Sachin D. Ghude

摘要

Airborne polycyclic aromatic hydrocarbons (PAHs) associated with particulate matter (PM) are recognized contributors to carcinogenic and oxidative health risks in urban environments, yet their size-resolved distribution and redox activity remain insufficiently characterized in megacities. This study presents an integrated observational assessment of 16 priority PAHs in PM₁₀, PM₂.₅, and PM₁ collected at an urban rooftop site in Delhi, India, during a winter early summer campaign (January–June 2024). Chemical speciation was combined with dithiothreitol (DTT) based oxidative potential measurements, molecular diagnostic ratios, Positive Matrix Factorization (PMF), and scanning electron microscopy energy dispersive X-ray spectroscopy (SEM–EDX) to examine size-dependent composition, source patterns, and health-relevant indicators. Total PAH concentrations exhibited pronounced temporal variability, with winter maxima (PM₁₀: 496 ± 36 ng/m3; PM₂.₅: 312 ± 19 ng/m3; PM₁: 212 ± 23 ng/m3), consistent with enhanced combustion emissions and reduced atmospheric dispersion. While PM₁₀ contained the highest total PAH mass, high-molecular-weight (5–6 ring) carcinogenic PAHs were preferentially enriched in PM₂.₅ and PM₁. The ultra fine particle fractions showed enhanced mass-normalized oxidative potential (OPm), with wintertime mean values reaching ~ 0.5 nmol/min/µg, indicating a greater capacity to induce oxidative stress per unit particle mass. PMF analysis identified traffic-related emissions, biomass burning, coal combustion, waste/plastic burning, and an aged/secondary combustion factor, although source mixing and atmospheric processing were evident. SEM–EDX observations revealed soot-like agglomerates with associated sulfur (S), potassium(K), and chlorine (Cl) signals, supporting mixed combustion influences. Screening-level health risk assessment using a U.S. EPA based inhalation model indicated that wintertime incremental lifetime cancer risk (ILCR) associated with PM₂.₅ and PM₁-bound PAHs approached or exceeded ~ 10⁻4, surpassing commonly applied acceptable risk thresholds and indicating a potential carcinogenic risk, particularly for adults. PM₁ accounted for a substantial fraction of PM₂.₅-associated cancer risk, underscoring the health relevance of ultrafine PAH-bearing particles. A composite particulate health risk index (PHRI) further suggested elevated potential risk for outdoor workers and socioeconomically vulnerable population groups. Overall, the findings highlight the disproportionate toxicological importance of fine and ultrafine PM-bound PAHs in Delhi and emphasize the need to target combustion-related sources to mitigate health-relevant exposures in megacity atmospheres.