References
material performance; and, ideally, participation in interlaboratory proficiency schemes. Harmonized, well-documented data are the precondition not only for reliable retrospective comparison but also for the data-driven predictive tools that the field ultimately needs. 3.2.7 Emerging and confirmatory techniques Beyond the mainstream methods, several developments bear on future comparability. Comprehensive two-dimensional gas chromatography offers dramatically improved separation of the crowded PCB congener suite and of co-eluting interferences, easing the resolution of individual congeners including problematic dioxin-like ones; a routine accredited GC×GC–μECD method has been demonstrated for PCBs, organochlorine pesticides, and chlorobenzenes in soil, sediment, and sludge (Muscalu et al., 2011). Complementary chemometric tools, notably positive matrix factorization applied to congener fingerprints, strengthen the apportionment of sediment PCBs to their sources (Karakas et al., 2017). Tandem and high-resolution mass spectrometry improve both selectivity and detection limits for trace congeners, which is essential for reliable TEQ characterization. Isotope-dilution quantification, using 13C-labelled congener standards, materially improves accuracy and cross-laboratory reproducibility and is the standard for the most rigorous dioxin-like analyses. Wider adoption of these confirmatory techniques, together with the harmonization measures already discussed, would narrow the methodological gap between laboratories and strengthen the data foundation on which any predictive framework must rest. 3.3 Human-health-risk assessment (Q3) 3.3.1 The USEPA deterministic framework The dominant paradigm for quantifying human-health risk in this literature is the deterministic framework associated with the United States Environmental Protection Agency, codified in its Risk Assessment Guidance for Superfund (USEPA, 2000) and the accompanying human-health evaluation manual (USEPA, 2009). In its standard form, exposure is expressed as an average daily dose for each relevant pathway, computed from the measured environmental concentration and a set of exposure parameters: ingestion or contact rate, exposure frequency and duration, body weight, and averaging time, with matrix- and pathway-specific factors such as soil-to-skin adherence and dermal absorption fractions for the dermal route and inhalation rates and particulate- emission factors for the inhalation route. Non-carcinogenic risk is characterized by dividing the ADD by a reference dose to obtain a hazard quotient (HQ) for each pathway and congener class, and summing across pathways and contaminants to obtain a hazard index (HI); an HI exceeding unity signals potential for adverse non-cancer effects. Carcinogenic risk is characterized by multiplying a lifetime average daily dose by a cancer slope factor to obtain an incremental lifetime cancer risk (LCR or ILCR), which is compared against acceptability benchmarks conventionally taken as 1 × 10−6 (nominally negligible) to 1 × 10−4 (upper bound of tolerability). 3.3.2 Exposure pathways Three exposure pathways are routinely evaluated for soils and dusts: incidental ingestion, dermal contact, and inhalation of resuspended particulates and, to a lesser extent, vapour. Across studies, incidental ingestion generally emerges as the dominant contributor to both non-cancer and cancer risk for soil and dust exposure, followed by dermal contact, with inhalation of particulates typically a smaller but non-negligible contributor. For dioxin-like congeners and for the general population beyond the immediate site, dietary intake (consumption of contaminated fish, poultry, eggs, and other locally produced foods) is frequently the pre-eminent pathway, reflecting bioaccumulation and biomagnification of the more persistent congeners; dietary-exposure and health-risk analyses of indicator PCBs (Kang et al., 2020), of bovine milk from an agricultural plain (Sana et al., 2023), and of domestic duck eggs as a discrete exposure route around recycling sites (Labunska et al., 2014) all illustrate this pathway. Where inhalation dominates, as near ambient PCB sources in urban India, risk has been quantified directly for the respiratory route (Goel et al., 2016). Receptor populations are typically stratified into occupational adults (workers) and nearby residents, with the latter often further divided into adults and children. Children are repeatedly identified as the most vulnerable receptor because of higher soil-ingestion rates and hand-to-mouth behaviour relative to body weight, greater dermal surface-area-to-mass ratios, and heightened developmental susceptibility. 3.3.3 Typical findings A consistent qualitative pattern emerges across the risk literature. For heavily contaminated hotspots, burning zones and intensive dismantling yards, deterministic assessments frequently report hazard indices exceeding unity, sometimes by substantial margins, for on-site workers and for children in the immediately surrounding community, indicating a plausible non-carcinogenic hazard. Incremental lifetime cancer risks at such locations commonly exceed the 1 × 10−6 benchmark and, at the most contaminated sites and for the most exposed receptors, exceed 1 × 10−4, placing estimated cancer risk above the conventional upper bound of acceptability. At the fringes of recycling districts and at reference locations, computed risks generally fall within or below the tolerable range. Dietary-pathway assessments, particularly those incorporating dioxin- like congeners and TEQ, can indicate exceedance of tolerable daily intakes for regular consumers of local high-trophic foods. Site-specific assessments echo this pattern, with hazard and cancer metrics computed for PCBs and PCDD/Fs in Indian recycling soils (Chakraborty et al., 2018), for air and soil across Pakistani recycling cities (Kazim et al., 2024), for Nigerian soils (Ediagbonya et al., 2025), and for PCB congeners in groundwater around Nigerian dumpsites expressed on a toxic-equivalency basis (Ololade et al., 2021). These findings are qualitatively robust across regions even though the precise numeric estimates are, for the reasons discussed under Q2, not strictly comparable across studies. 3.3.4 Probabilistic and mixture-aware extensions A minority of studies extend the deterministic framework toward probabilistic characterization, replacing point-estimate exposure parameters with distributions and propagating them through Monte Carlo simulation to yield a distribution of risk across a population rather than a single value. Such approaches better represent the reality that exposure varies widely among individuals (a worker who burns cable daily and a resident several streets away occupy very different positions on the risk distribution), and they allow explicit statements about the fraction of a population exceeding a hazard or cancer benchmark and about the parameters that most influence the result. Sensitivity analysis within these frameworks consistently identifies soil-ingestion rate, exposure duration, and body weight as dominant drivers, reinforcing the vulnerability of children. Equally important is the treatment of PCBs as one component of a co-contaminant mixture; cumulative- risk approaches that sum contributions across chemicals with common effects, and that
