Are unreported technical polychlorinated biphenyl formulations used in legacy building materials threatening indoor environments of a central Indian City despite the ban?

Uniform predominance of lower- and mid-chlorinated polychlorinated biphenyls (PCBs), including PCB-8, -18, -28, -44, -52, -66, -101, -105, -118, -138, and -153, across urban and suburban/rural indoor dust from a central Indian city indicates strong influence of open, partially open and closed application technical formulations used in built environments that remain largely unaccounted in India's National Implementation Plan. Mean of Σ28 PCBs (103.3 ng/g) and Σ12 DL-PCBs (30 ng/g) were strongly influenced by urban outliers. Homolog profiles were dominated by lower to mid-chlorinated congeners (di - hexa), accounting for more than 94% of total PCBs, with uniform distribution across urban and suburban/rural sites. No statistically significant differences were observed in household characteristics or PCB levels between urban and suburban/rural sites. However, residences above 20 years exhibited higher PCB loading in urban hotspots. Despite this trend, lack of statistical significance indicates that building age alone may not be the primary influencing factor. Strong correlations with open, partially open, closed application formulations (Aroclor 1248, Kanechlor 400, Clophen A50, Kanechlor 500, and Pyralene DP-3) indicated source profiles consistent with congener fingerprints. Congener-specific fingerprints suggested legacy building materials, localized combustion, vehicular and workshop operations, domestic emissions and coal-powered industrial facilities as possible sources. Site-specific exceedances of hazard indices (HI > 1) at urban hotspot locations for adults and children are predominantly driven by dermal exposure. Incremental lifetime cancer risk exceeded regulatory benchmarks for adults at multiple urban hotspots, suggesting indoor PCB exposure in India may be underestimated due to undocumented sources within the built environment.