Polychlorinated biphenyls (PCBs) are a family of 209 persistent organochlorine compounds manufactured between the 1930s and 1970s for use as electrical insulating fluids, hydraulic oils, and flame retardants. They were globally banned or severely restricted by the 1970s and 1980s, yet remain ubiquitous in the environment due to extreme persistence. PCBs bioaccumulate in fatty tissue and biomagnify through food chains — meaning fatty fish, meat, and dairy products continue to deliver measurable PCB doses to humans 50 years after production ceased. IARC classifies the PCB mixture as a Group 1 confirmed human carcinogen.
Where it's found
Fatty fish are the primary dietary PCB source: salmon (especially farmed), mackerel, herring, sardines, eel, and tuna. The PCB content of farmed salmon has historically been substantially higher than wild-caught due to PCB accumulation in fishmeal-based feed. Dairy products including butter, cream, cheese, and full-fat milk. Meat — particularly liver and fatty cuts from animals grazing on contaminated land. Human breast milk — PCBs are reliably detected in breast milk of women worldwide and represent a significant neonatal dose. Indoor air and dust in buildings containing old PCB-sealed electrical equipment, fluorescent light fittings, and old caulking.
Routes of exposure
Dietary ingestion of lipophilic PCBs from fatty food is the dominant route — PCBs partition into fat and are absorbed efficiently from the gut. Breast milk transfer to infants during nursing. Inhalation and skin contact in buildings with PCB-containing materials (old office buildings and schools with 1960s–1970s construction). PCBs accumulate progressively in human adipose tissue over a lifetime — body burden reflects the cumulative sum of all exposures, with a biological half-life of years to decades for individual congeners.
Health concerns
IARC classifies PCB mixtures (Aroclors) as Group 1 carcinogens based on sufficient evidence in humans and animals. Epidemiological studies link elevated PCB body burden to non-Hodgkin lymphoma, liver cancer, breast cancer, and thyroid cancer. PCBs are potent endocrine disruptors: dioxin-like PCBs activate the aryl hydrocarbon receptor (AhR), disrupting sex hormone and thyroid hormone signalling. Prenatal PCB exposure is associated with impaired neurodevelopment, lower IQ, and attention deficits in cohort studies of children. PCBs suppress immune function. The thyroid-disrupting effects are particularly well characterised — PCBs compete with thyroid hormones for binding to plasma transport proteins, reducing circulating levels.
Evidence
IARC Group 1 classification reflects strong human and animal carcinogenicity evidence. Neurodevelopmental effects from prenatal exposure are supported by multiple prospective birth cohort studies (Faroe Islands, Great Lakes, Dutch cohorts). Thyroid disruption is mechanistically and epidemiologically well characterised. The evidence base is among the most complete for any environmental persistent organic pollutant.
Who's most at risk
Pregnant women and breastfeeding mothers have the highest concern given transplacental and breast milk transfer to the foetus and neonate during critical developmental windows. Foetuses and infants are the most vulnerable to neurological effects. People consuming fatty fish or full-fat dairy multiple times per week have higher dietary intakes. Older adults carry the highest body burdens due to decades of accumulation.
Regulatory status
RegulationPCBs are banned from manufacture under the Stockholm Convention on Persistent Organic Pollutants (2001), ratified by over 180 countries. EU maximum limits for PCBs (as indicator PCBs) in food are set under Regulation (EC) 1881/2006. UK retained these limits post-Brexit. Ongoing legacy contamination means monitoring programmes continue to find exceedances in some fish products. Buildings containing PCB materials are subject to management and remediation requirements in most European countries.
How to reduce your exposure
Vary oily fish sources — wild-caught oily fish from cleaner waters (sardines, anchovies, herring) tend to carry lower PCB burdens than farmed salmon. Trim fat from meat and avoid liver products from animals from potentially contaminated areas. Choose lower-fat dairy options where possible, as PCBs concentrate in the fat fraction. Pregnant women and those planning pregnancy should follow national guidance on oily fish consumption limits. Grilling or baking fatty fish allows fat (and PCBs) to drip away from the flesh, reducing exposure compared to frying.
The nutrition connection
The PCB story represents a critical challenge for dietary guidance: oily fish provide DHA and EPA omega-3 fatty acids with strong evidence for cardiovascular and neurodevelopmental benefit, yet the same fat carries legacy persistent organic pollutants. The resolution lies in fish source selection and preparation — smaller, shorter-lived species (sardines, anchovies, herring, mackerel) accumulate less PCB than large, long-lived predators. This nuance — that the nutritional case for oily fish depends on which fish — is exactly the kind of integrated food and environment analysis that Nutriofia exists to provide.