polychlorinated biphenyls (PCBs (chemical))

Polychlorinated biphenyls (PCBs) — distinguished here by lower-case to differentiate from printed circuit boards which share the acronym — are a class of persistent organic pollutants consisting of biphenyl molecules with 1-10 chlorine substituents, used industrially from 1929 through the 1980s as dielectric fluid in transformers and capacitors, plasticisers, hydraulic fluids and heat-transfer fluids. The Stockholm Convention listed PCBs under Annex A in 2004, mandating elimination of use in equipment by 2025 and environmentally sound disposal by 2028. India is a signatory and has notified national implementation through the Hazardous and Other Wastes (Management and Transboundary Movement) Rules 2016.

The hazard during e-waste and electrical equipment recycling is acute. Encountering a PCB-bearing transformer or capacitor in the scrap stream creates four risk vectors. Worker exposure: PCBs are absorbed through skin contact with leaking oil and through inhalation of vapours during cutting or torching — biomarkers (serum total PCB, PCB-153 specifically) in informal-sector electrical scrap workers in India have shown levels 5-50x background population means. Soil and groundwater contamination: a leaking 1-tonne transformer can contaminate a 100-200 m² soil area to PCB concentrations of 10,000-50,000 mg/kg, requiring excavation and incineration of the contaminated soil at Rs 30-80 per kg disposal cost. Air emissions: open burning of PCB-bearing materials (still observed in informal scrap yards) releases PCBs unchanged and generates polychlorinated dioxins and furans. Material contamination: PCB-contaminated copper wire and transformer steel, if introduced into clean recycling streams, contaminate downstream products.

Identification of PCB-bearing equipment in the field follows manufacturer date and oil type. Equipment manufactured before 1985 using mineral-oil-filled or askarel-filled (the trade name for PCB-containing fluids: Aroclor, Pyranol, Inerteen, Clophen, Pyralene, Sovol) construction is presumed PCB-bearing until tested. The L2000DX or equivalent chlor-N-oil field test gives 5-10 minute presumptive identification at >50 mg/kg. Confirmation requires GC-ECD or GC-MS at NABL labs at Rs 1,500-3,500 per sample. Once identified, PCB-bearing equipment must be drained under containment, the oil sent for high-temperature incineration (above 1,100°C, retention >2 seconds, rapid quench to prevent dioxin formation in 300-450°C cooling zone) at CPCB-authorised TSDFs, and the transformer steel and copper triple-rinsed with organic solvent before regranulation.

For Indian recyclers, the operational discipline is conservative pre-screening. Pre-acceptance protocol: every transformer and large capacitor offered for purchase is dated and inspected; pre-1990 units are tested before any handling. Storage: PCB-bearing equipment is segregated in a roofed, bunded containment area with secondary containment to 110% of oil volume, away from process lines. Disposal economics: handling and disposal cost runs Rs 200-500 per kg of PCB-bearing material, against scrap value of Rs 200-400 per kg from the steel and copper — typically the operation runs at break-even or slight loss but is necessary to maintain CPCB authorisation status. The pragmatic trade-off is that mixing PCB equipment into general transformer scrap to avoid the disposal cost is a catastrophic risk — CPCB raids on improper PCB handling lead to immediate facility closure and personal criminal liability for the occupier.