PCBs as Endocrine Disruptors

PCBs deserve a special mention for a number of reasons. Over relatively short period of time family of synthetic chemicals has become the most widely distributed artificial chemical to be incorporated into living systems. Nearly all forms of life contain PCBs.
Yet it is not natural. And in sufficiently high concentrations (over seventy parts per million) it disrupts the immune system and damages the reproductive systems of animals. But even in very low amounts it can act as an endocrine disruptor and interfere with the proper functioning of the endocrine system.
PCBs were first created in 1929. It was created by combining chlorine atoms with two joined benzene rings called biphenyls. From the various permutations possible a family of chemicals comprising of 209 members collectively called polychlorinated biphenyls was created.

 

The uses of PCBs

PCBs were the perfect chemicals for the industrial age. It found use in nearly every possible industrial process. But its primary use was as a non-flammable cooling compound in transformers. It became a standard chemical in the electrical industry. It also found uses as lubricants, hydraulic fluids, cutting oils and liquid seals.
It eventually found its way into the home, when it was discovered that it made wood and plastics non-flammable and made certain materials waterproof.

 

PCBs in living systems

The ubiquitous nature of PCBs within living systems was discovered inadvertently in 1964 by Danish scientist Sören Jensen. While investigating DDT levels in human blood, he discovered a number of anomalous peaks that kept showing up in his results.
He soon realized that the peaks showed up everywhere in nature, from decades old wildlife specimens to animals in his local park. He even discovered peaks in samples taken from his wife and daughter.

 

How much PCBs was produced?

The U.S didn’t ban the manufacture of PCBs until 1976. Other industrial countries eventually followed the United States example. But PCBs had been manufactured globally for more than 50 years. It is estimated that more than 3.4 billion pounds of PCBs was produced in over half a century of use, most of which was already lost to the environment.
PCBs are still present in quite a few appliances and it will be a few decades still until all the manufactured PCBs is eventually released into the environment.

 

PCBs were Persistant, Bioaccumulative and Toxic (PBT)

Why did they pervade nature so thoroughly? PCBs like its cousin DDT had a tendency to bioaccumulate in fat. And like DDT it had the ability to accumulate the further up the food chain you went.
However, PCBs was much more stable than DDT. In fact PCBs was impervious to everything, except ultraviolet B from the Sun. It was extremely persistent. But it was also very volatile, which meant it could be carried in the air for very long distances if the conditions were right. And of course PCBs were toxic. It had a dangerous combination of qualities that made it the worst kind of synthetic chemical, the kind that had the ability to permeate every corner of nature.

 

Humans are top predators. We all take in more synthetic chemicals into our systems than we should. It is a well known fact that nearly every single human being contains more than 250 different chemical pollutants in their body fat. No matter where you live, you can’t escape contamination; such is the ubiquity and prevalence of artificial man-made chemicals.
PCBs introduces us to the real dangers of certain types of chemicals, dangers that we didn’t initially anticipate and therefore couldn’t predict. It reminds us that certain chemicals can be extremely persistent but they can also have the capacity to integrate themselves into biological systems.
The persistence of PCBs means that it could theoretically continue to accumulate to even higher levels in all forms of life, especially in the top predators.