PCBs short for polychlorinated biphenyls (PCBs) were widely used as flame retardants in electronic devices and material including in appliance capacitors and fluorescent light ballasts to prevent fire. It was also used in other household products.

PCBs are one of the "dirty dozen" pollutants banned in 1972 by the United Nations' Stockholm Convention on Persistent Organic Pollutants due to their evident toxicity.  

PCBs are chemicals that remain intact in the environment for long periods and humans would accumulate potentially them in the body triggering diseases like cancer.   According to the United States Environmental Protection Agency, an average person in the US gets a few micrograms of PCBs each day.

For the study published in the current issue of Environmental Science and Technology, Stuart Harrad from the University of Birmingham in the UK and colleagues monitored PCBs in outdoor air and surface soil samples monthly for one year at ten locations on a rural-urban transect across the West Midlands of the UK.

They found that the West Midlands conurbation is a source of PCBs to the wider environment.   But concentrations of PCBs in the outdoor air samples were lower than those reported early for indoor air in the same area.

The researchers their finding suggests strongly that "the principal contemporary source of PCBs in this conurbation is ventilation of indoor air and not volatilization from soil."

“We now have two comprehensive studies that have investigated the plume of PCBs in urban areas, both implicating indoor air as the major source and both showing strong gradients as you move away from the most heavily populated areas,” Tom Harner, a research scientist with Environment Canada was quoted as saying of recent measurements of the sources of PCBs in and around Toronto.

Although PCBs have been banned for a long time and their presence in the environment is declining, humans are still at high risk of exposure to these pollutants.   The EPA agrees that "breathing indoor air and consuming fish contaminated with PCBs have been identified as major sources of exposure,", the EPA says in a document titled "Management of Polychlorinated Biphenyls in the United States", which was released in January 30, 1997.

Currently the flame retardants which replace PCBs are polybrominated diphenyl ethers (PBDEs), which are chemically similar to PCBs. Experts are concerned that these chemicals now widely used in household products such as carpets and cases of electronic products such as computers and TVs may impose the same or similar risks to human health as PCBs do.

The authors of the current study write that “Future reductions in PCB concentrations in outdoor air and ultimately human exposure appear best achieved by action to remove remaining sources of PCBs from existing structures.”

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