Why are Banned Chemicals Still Releasing Their Toxicity

Polychlorinated biphenyls (PCBs) were widely used in industrial and commercial products including plastics, paints, electronic equipment, and insulating fluids. Their manufacture was extensively banned from the late 70s onwards due to their toxicity. However, large amounts remain in our environment and accumulate inside animals’ bodies. For the United States, the 20th century was an exciting time of innovation in industry and advances in technology. Sometimes, however, technology races ahead of responsibility, and human health and the environment can suffer as a result. This is certainly the case for the toxic compounds known as polychlorinated biphenyls or PCBs.

From the 1920s until they were banned in 1979, the U.S. produced an estimated 1.5 billion pounds of these industrial chemicals. They were used in a variety of manufacturing processes, particularly for electrical parts, across the country.

Wastes containing PCBs were often improperly stored or disposed of or even directly discharged into soils, rivers, wetlands, and the ocean. Unfortunately, the legacy of PCBs for humans, birds, fish, wildlife, and habitat has been a lasting one.

What are the Adverse Health Effects of PCBs Exposure?

PCBs are hazardous even at very low levels. When fish and wildlife are exposed to them, this group of highly toxic compounds can travel up the food chain, eventually accumulating in their tissues, and becoming a threat to human health if eaten.

They have two mirror-image isomers that are identical reflections of each other with the same composition. These types are particularly dangerous because they have more chlorine atoms, which are hard for the body to break down, so they can accumulate in the body easily and their isomers are metabolized differently, causing isomer-specific toxicity (particularly neurodevelopmental issues).

However, the process behind this selective metabolism was not known. To address this, a research group has illuminated how enzymes produced by the body unevenly metabolize the mirror-image isomers. These results published in the journal Environmental Science & Technology will make it possible to estimate PCB metabolism and detoxification pathways in animals.

They will also contribute towards the development of technology to make predictions about chiral PCBs’ mirror isomers so that we can obtain a better understanding of potential toxicity in humans and other mammals.

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The amount of time that it takes chemicals such as PCBs to break down naturally depends on their size, structure, and chemical composition. It can take years to remove these chemicals from the environment and that is why they are still present decades after they have been banned.

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Source-Eurekalert