Effects of Polychlorinated Biphenyls (PCBs) on Humans

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Originally posted 2016-08-29 06:31:26.

The Effects Polychlorinated Biphenyls (PCB)On Humans 


Polychlorinated Biphenyls (PCBs) are man-made Organic chemicals known as Chlorinated Hydrocarbons. They are made of Carbon, Hydrogen and Chlorine atoms. These atoms can be combined in many different ways and 209 different PCB molecules can be formed. Some are more harmful than others. The coplanar PCBs, known as non-ortho PCBs tend to have dioxin-like properties and are among the most toxic congeners.

PCBs range in appearance from colourless, oily liquids to more viscous and increasingly darker liquids or resins ranging in colour from yellow through to black, depending on the chlorine content. Polychlorinated Biphenyls (PCBs) were domestically manufactured from 1929, but banned in several countries in 1979. PCBs are chemically stable, have good insulating properties and do not degrade appreciably over time or with exposure to high temperatures.

 

These properties make PCBs very useful in electrical devices such as capacitors. PCBs released into the environment do not readily breakdown and can accumulate in fatty tissues of animals.

Products That May Contain PCBs Include

  • Oil used in hydraulic systems and motors
  • Oil based paints
  • Dish washer
  • Pesticides 
  • High intensity lighting systems used in industries and roads
  • Heat transfer system
  • Thermal insulation materials
  • Transformers (dielectric fluid) , capacitors and other electrical equipments
  • Plastics

How PCBs Can Be Released Into the Environment

 

PCBs can be released into the environment from poorly maintained hazardous waste sites that contain PCBs; Leaks or releases from electric transformers; improper dumping of PCB wastes and improper dumping of PCB containing products. PCBs released into the environment do not readily break down and can accumulate in fatty tissues of animals. PCBs longevity and their affinity for any fatty tissue can result in PCBs concentration through food chain. PCBs can be exposed to humans through food, breathing contaminated air and skin contact. PCBs biomagnifies up the food web and are present in fish and waterfowl of contaminated aquifers.

 

Animals that ingest smaller amount of PCBs in food develop various health effects including anaemia, liver, stomach, thyroid gland injuries and thymocyte apoptosis. PCBs in the air can reach the ground with falling rain or simply when suspended particles settle with gravity.

There  level in the air have been found to be lower in rural and remote areas than in urban and industrial areas. Indoor air concentration of PCBs is ten times higher than in outdoor. PCBs stick strongly to the soil and will not usually be carried deep into the soil with rain water. PCBs do not easily break down in the soil and can stay for months and years. The lighter PCBs leave the soil through evaporation and as a gas it accumulates in the leaves, plants and food crops. Devices that contain PCBs leak as they get older thereby entering into the soil and water. These devices also release small amount of PCBs into the air when they are hot.

 

Humans can be exposed to PCBs when swimming in contaminated water, drinking contaminated water, breathing PCB- contaminated air, ingesting PCB – contaminated food and skin contact with PCBs contaminated substances.

 

PCBs in the body can be changed into metabolites. Some metabolites of PCBs may have the potential to be as harmful as unchanged PCBs. Some leave the body through faeces, while the rest remain in the body mainly in the fat and liver and smaller amounts can be found in other organs.

PCBs Definition

PCB material can be said to be ‘Scheduled’ if the concentration of PCBs in the material is at least 50mg/kg.

 

It is ‘concentrated’ if the concentration of PCBs in the material is at least 100,000 mg/kg.

 

Non – Scheduled PCB material means any material which contains PCBs at levels below the threshold concentration (50 mg/kg) or threshold quantity (50g) and above the concentration level considered as PCB free (2mg/kg).

 

PCB – free is non PCB material.

 

Recent Data Analysis conducted in some parts of Nigeria shows that more than 80 % of PCBs contaminated materials are in existence.

 

How to Identify Equipments Containing PCBs

 

Use Of Available Documentation – The hand book of equipments contain the name, product code and PCB status of electrical component.
Date Of Manufacture – Equipments produced after 1979 are PCB- free.
Sampling – When there is only limited information available of the equipment, the most appropriate way to determine the PCB status is to send a sample of the material ( e.g. Dielectric fluid from the equipment) to an accredited laboratory to determine whether or not it contains PCBs.
Note: PCB contaminated equipments should be managed and treated by experts.

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