Perhaps the most widely known of organic contaminants, polychlorinated biphenyls (PCBs) are a serious environmental problem due to their wide-dispersal and extreme persistence in the environment. Used in a variety of industrial and commercial purposes, PCBs were readily manufactured from the 1930s until studies showing adverse environmental effects resulted in production bans by many countries. Today, regulations are in place governing the storage, distribution, use and disposal of PCBs.
PCBs are synthetic chemical compounds consisting of two benzene rings, each containing from 1 to 5 chlorine atoms, connected by a single carbon to carbon bond. The toxicity of a PCB is dependent on the number and the position of the chlorine (ortho, meta, and para positions). There are 209 possible congeners with the 12 most toxic displaying “dioxin like” effects. The “dioxin-like” PCBs have chlorines in at least four of the lateral position and no more than one of the ortho positions. PCBs with no chlorine substitution in the ortho position are referred to as coplanar PCBs. Since PCBs were often manufactured as a formulationof specific congeners, mixtures are often referred to by their commercial formulation name, e.g. “Aroclor 1254”.
PCBs were widely used as dielectric and heat exchange fluids in applications such as transformers and capacitors, due to their stability, insulating, and low flammability properties. It is estimated that between 900,000 and 1,200,000 metric tonnes of PCBs have been produced globally. While knowledge of the effects of PCBs led to production bans and phase outs of their uses in the 1970s and 1980s, elimination of PCB containing equipment and products continues today. PCBs enter the environment most often through incorrect disposal methods – incineration, placement in municipal landfills and direct discharge into the environment. They are subject to long-range transport by global air currents and, once deposited, bioaccumulate in the food chain.
Current human exposure to PCBs is primarily through food consumption of fish, meat and dairy products and through exposure from airborne sources. PCBs have been shown to be carcinogenic and may interfere with nervous, endocrine, reproductive, and immune function.
AXYS specializes in measurement of PCBs to picogram or lower concentrations from standard sample sizes. Our specialized sampling and analytical procedures may allow for much lower detection limits and reduced sample sizes in human and sediment matrices. We deliver legally defensible data under ISO 17025 certified systems applying methods accredited by NELAP and CALA. Electronic Data Deliverables (EDD), customized for download to our clients’ relational databases, are available in addition to standard format report and full data packages.