What are Polychlorinated Biphenyls?
Polychlorinated biphenyls (PCBs) are a group of high production industrial chemicals manufactured from 1929 until banned in the United States in 1979. The group includes 209 individual chemicals, known as congeners. Out of 209 possible PCB congeners, 120-140 are formed in commercial mixtures widely known under the US branded tradename Aroclor. Other commercial mixtures from different global producers include Clophen (Germany), Kanechlor (Japan), Phenochlor (France), and Ascarel (Brazil). Other congeners, known as incidental PCBs, can be formed as a by-product of another manufacturing process, or from the breakdown of a PCB from commercial mixtures. PCBs are considered ubiquitous in the environment, meaning levels can be found in virtually every environmental and biological specimen across the globe.
What are they used for?
The chemical and physical stability of PCBs were desirable in a variety of industries. There are several Aroclor products, distinguished by the percent chlorine by weight in the formulation. PCBs were used in transformers, capacitors, plasticizers, hydraulics, lubricants, and carbonless copy paper. PCBs are no longer manufactured, but there are products in use today that contain PCBs (e.g. transformers, caulking) (US EPA, 2019) .
Where can they be found?
Levels of PCBs in the environment have been declining, but a measureable amount can be found in most environmental and biological samples. PCBs are lipophilic, meaning they have poor solubility in water and will distribute to other lipophilic substances, such as organic matter found in soils and sediments. In biologics, PCBs are distributed in the lipid (i.e. fat) components of tissue and blood serum. Higher concentrations of PCBs are found in humans compared to fish or birds, because the chemicals bioaccumulate up the food chain.
Why are they important?
Several national and international organizations, such as the International Agency for Research on Cancer (IARC), the Department of Health and Human Services (DHHS), and US Environmental Protection Agency (EPA) have classified PCBs as probable human carcinogens. PCBs are persistent organic pollutants (POPs), meaning they do not easily break down in the environment. A distinct group of PCBs have toxicological effects similar to polychlorinated dibenzo-p-dioxins (PCDDs or dioxins) by binding to the Ah receptor. The spatial structural requirement results in 12 co-planar congeners, which are considered to be the most toxicologically relevant PCB congeners. These co-planar congeners are at very low levels in Aroclors and other commercial mixtures.
- Legal Sampling
- Chain of Custody
- Study Design
- Data Analysis and Visualization
- Data Wrangling
- Multivariate Statistical Analysis
- Principal Component (PCA); Hierarchical Cluster (HCA)
- Science Communication
- Data Science/Big Data
- Multidimensional Gas Chromatography (GC×GC)
- Source Apportionment
- Chemical Fingerprinting
- Diagnostic Ratios
- Fate and Transport
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Chemistry Matters Consulting Services and Expertise
The problem of PCB contamination has been studied for over 50 years and will continue to be studied for many years (decades) to come. Removal of PCB containing products, remediating contaminated sites, evaluating health effects, and recouping costs from potentially responsible parties is a burden many communities are facing. The Chemistry Matters team is well suited to assist in many of these endeavours. We have the litigation experience required for expert witness testimony and are actively involved in PCB related research by publishing in peer-reviewed journal articles and presenting at scientific conferences.