Polychlorinated Biphenyls (PCBs) are a group of man-made organic chemicals consisting of carbon, hydrogen and chlorine atoms with aromatic rings (eg. Doxin, Furan, PCB) and they belong to Persistent Organic Pollutants (POPs).
PCBs, manufactured in the United States from 1929 to 1977, were used widely as insulating fluids in electrical equipment such as transformers and capacitors, as well as in hydraulic systems, surface coatings, and flame retardants.
Their chemical properties, such as non-flammability, chemical and thermal stability, dielectric (eg. nonconductor) properties, and miscibility (eg. capable of being mixed) with organic compounds, were responsible for many of their industrial applications.
However, the negative health effects that have been associated with exposure to PCBs include acne-like skin conditions in adults and neurobehavioral and immunological changes in children, which have been recorded in scientific publications with evidence from all over the world. Therefore, the manufacturing of PCBs was banned in 1979.
From where do they come?
 Bio accumulation and bio magnification of hazarders PCBs in the environment
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Due to their non-flammability, chemical stability, high boiling point and electrical insulating properties, PCBs were used in hundreds of industrial and commercial applications.
The Environmental Protection Agency (EPA) in the USA, has estimated that more than 200 chemical processes can inadvertently generate PCBs. Products that might be a new source of PCBs include; electrical, heat transfer and hydraulic equipment, coolants and lubricants in transformers, capacitors, plasticisers in paints, plastics and rubber products, pigments, dyes and carbonless copy paper, fluorescent light ballasts, cable insulation, thermal insulation material including fiberglass, foam and cork, adhesives and tapes, floor finish and many other industrial applications are some examples.
PCBs could enter the air, water, and soil during their manufacture, use, and disposal; from accidental and leaks during their transport; and from leaks or fires in products containing PCBs. Another continuing source of PCBs is recycling activities that keep PCBs in circulation for many years to the environment from hazardous waste sites.
Illegal or improper disposal of industrial wastes and consumer products; leaks from old electrical transformers containing PCBs; and burning of some wastes and open dumping are common sources.
What happens to PCBs when they enter the environment?
Humans and wildlife can be exposed to PCBs either directly from contact with contaminated air, sediments, or water or indirectly through the diet. Consumption of PCB-contaminated foods is the most significant route of exposure to PCBs for the general human population. However, PCBs do not readily break down once in the environment.
They can remain for long periods cycling between air, water, and soil and can be carried long distances and have been found in snow and sea water in areas far from where they were released into the environment.
As a consequence, they are detected all over the world and this scenario is called as ‘global distillation’. In water, a small amount of PCBs may remain dissolved, but most stick to organic particles and bottom sediments, and therefore, bind strongly to soil and can accumulate in the leaves and above-ground parts of plants and food crops.
Exposure to PCBs
Using old fluorescent lighting fixtures, electrical devices and appliances such as television sets and refrigerators that were manufactured 30 or more years ago contain PCBs.
These items may leak small amounts of PCBs into the air when they get hot during their operations and could be a source of skin exposure. The main dietary sources of PCBs are contaminated fish, meat, and dairy products.
Breathing air near hazardous waste sites and drinking contaminated well water also are possible routes.
In the workplace, during repair and maintenance of PCB transformers; welding plants, fires or spills involving transformers, fluorescent lights, and other old electrical devices; and disposal of PCB materials are also possible sources.
Contamination through welding plants
Waste substance and articles containing or contaminated PCB and Phenylthiocarbamide (PTCs) and Polybrominated biphenyl (PBB) are included as a waste stream in Schedule 1 of the Regulation No. 1 of 1990, of the National Environment Act, as amended by Gazette Extraordinary No. 595/16 of 1990 in Sri Lanka.
Sri Lanka became a signatory to the Stockholm Convention in September 2001 and ratified this Convention on December 22, 2005. Under this regulation, no person shall collect, transport, store, recover, recycle or dispose waste containing or contaminated with PCBs or establish any site or their disposal, except under the authority or a licence issued by the Central Environment Authority (CEA) of Sri Lanka.
Under the provisions of the Stockholm Convention, Sri Lanka is required to completely phase out the use of PCBs and dispose of any stocks of PCB in an environmentally safer manner by 2028.
Nevertheless, it is a well-known fact that PCBs are released into the environment by unauthorised human activities especially through welding plants in Sri Lanka.
 Major types of POPs in the environment |
Although transformers and capacitors containing PCB coolant oils and dielectrics are no longer imported to Sri Lanka, PCB-containing coolant oil from discarded or damaged transformers and capacitors continues to be indiscriminately used for a variety of purposes.
Transformers and capacitors that were imported to the country prior to the adoption of the convention are now entering the salvage yards following their decommissioning or damage, where they are stockpiled for disposal. The transformer oil is extracted from such equipment and used for other purposes by certain small and medium scale industries is common and it is continuing to date.
It also should be noted that PCBs could get into the aquatic system via surface water run-off and leads to bioconcentration and bioaccumulation via food chain allowing biomagnifications in the higher trophic level of the food chain. Under the National Environment Act, standards have been proposed for inland water bodies via organic micropollutants in ‘inland waters where fisheries and aquatic life are to be protected’, with a limit of 1 nanograms per liter of PCB (total) as the maximum acceptable level.
Thus, it is important to know and do research studies to detect the level of PCB contamination in ground level and to find PCB contamination via welding plants, which are one of the important ways in which PCBs are released into the natural environment via human activities.
A survey conducted by UNDP Sri Lanka shows that 48% of the transformers available were manufactured on or before 1986 and are contaminated with PCBs. Recent studies indicate that around 17,528 transformers owned by the Ceylon Electricity Board (CEB) and 2,700 owned by Lanka Electricity Company Private Ltd, are contaminated with PCBs. In addition, there are around 74 transformers owned by independent power producers that has this contaminant.
These statistics might have been changed by now as government has taken steps to address this problem. The Ministry of Environment of Sri Lanka tested 176 of the 681 transformers manufactured by 1986 and found that 60% of the tests were positive for PCBs (over 50 ppm).
There is anecdotal evidence to suggest that coolant oil extracted from discarded transformers is widely used as coolant oil in small-scale welding facilities operated in Sri Lanka. A study conducted by the author and his team in Kaluthara district revealed that 78% of the welders were between the ages 35 to 54 years and their family consisted of 3 to 5 members. 60% of them had attended school only up to grades 9–11, and 30% had completed only up to grades 6–8.
Therefore, it was understood that participants of the study were poorly aware of the negative environmental and health implications of PCBs. When considering about their exposure in welding plants, 60% operated their welding plants for five days a week, while 32% of the plants were operated for 6 days a week, and the rest were in operation in all 7 days.
Further, it was noted that 90% percent of welders in the study worked between a periods of 7–10 hours a day. It was observed that around 30% of the workplaces were operated within their homes, and 80% of welding plants were totally open while being heated during their operations.
They use coolant oil in the welding equipment in order to facilitate heat transmission and thereby assist in the cooling process. According to the welding owners, about 30% of the workplaces, replaced coolant oil in every 2-3 years.
In some cases, oil replacing was done in every 5–6 years. During this study, it was observed that none of workers or owners wore protective equipment or used protective measures, or at least wore hand gloves while filling the welding equipment with coolant oil.
Further, it was noticed that almost all welders used discarded coolant oil, which was previously used in transformers as the coolant oil. The majority (80%) of workers reported that they purchased transformer oil from private businesses where engine oil and other lubricants were sold. Interestingly, it was found out that around 20% of workers purchased coolant oil from employees of the Ceylon Electricity Board (CEB).
Not only that, some workers purchased the coolant oil from fuel filling stations and transformer oil was available at a lower cost. In terms of exposure to PCBs, was during repairs, it was observed that there are high risks of exposure to PCBs via transformer oil as their hand and clothes are continuously exposed to contaminated oil.
During the study, some workers stated that the transformer oil was applied to wounds of their family members and domestic animals as it has a soothing effect.
Further, the study revealed that 96% of welders had no knowledge about health effects on being exposed to transformer oil. It was observed that gloves were used only by a minority, even when attending to maintenance work of the welding equipment that exposed them to PCB-containing coolant oil which could get absorbed through the skin.
The housekeeping practices of welding plant workers were extremely poor in all of the workplaces that were observed during the study. In this study, it was found that 68% welding plant coolant oil samples were positive for PCB and the concentrations were ranged from 66 to 279 ppm, which are noted to be extremely high.
PCB-contaminated transformer oil in discarded transformers has been identified as a potential threat and the possible route cause for PCB contamination in Sri Lanka. However, until now, there has only been anecdotal evidence to suggest that PCB-contaminated transformer oils were used for numerous purposes in informal sector industries.
Evidence from recent studies has shown that PCB contaminated transformer oils pose a more serious and widespread hazard than anticipated in Sri Lanka. Burning empty containers with residues of PCBs, throwing away empty containers and disposing coolant oil in the home garden when replacing new oil was also identified as major risks of PCB exposure to humans and animal life, including contaminating the environment.
When PCBs burn, they can form toxic substances such as dioxins and furans, whose highly toxic and deleterious effects on health have been well documented all over the world.
The workers’ lack of awareness regarding the health and environmental risks of PCB-contaminated coolant oil was identified as a key contributor to unsafe practices in many studies.
The practice of applying transformer oil on wounds of animals and sometimes those of humans showed that they were totally uninformed about the harmful properties of the oil, particularly that it could be absorbed through the skin. Further, it should be highlighted that good hygienic practices such as changing into working clothes before starting work and washing with soap and water, and changing into home clothes after working, were not practiced by all of the workers.
As a result, workers may carry PCBs to their homes on their clothes, body, or tools, thus passing them on to their family members, particularly to their children. As a result, there is a high risk of contaminating family members through soiled clothes and contaminated bodies of the workers.
The widespread indiscriminate use of PCB contaminated transformer oil is a hazard and it is imperative that environmental authorities take immediate action to identify PCB-contaminated equipment in Sri Lanka and enforce legislation to prevent seepage of these toxic substances into industries and communities.
Health effects due to welding exposure
Available information between exposures and effects are strengthened by observation of a positive dose-response relationship, which are well documented from scientific studies in the world.
The studies say, if there are cumulative health effects, they would be expected to be more prevalent and more pronounced among those with longer welding experience. In most of the epidemiological studies, welder’s length of employment in the profession is often used as an indication of the cumulative dose from exposure to welding fumes.
A positive duration-effects relationship was found by in a study of young shipyard welders, where during their first 9 years in the trade, who showed changes in respiratory reactivity.
These changes, which could be signs of progress toward the development of asthma were related to years of employment as welders. In another study, it was found out that lung cancer mortality was significantly associated with duration of exposure to welding fumes up to 15 times.
Several other investigators found a significantly higher incidence of self-reported asthma among welders than in the general population, but the incidence was highest among welders younger than 45 years old and another study found a significantly increased risk for uveal melanoma (cancer of the eye) among welders that was unrelated to years of welding experience.
In three studies conducted by a group of Ukrainian investigators on welders, which focused on chronic iron overload syndrome (hemochromatosis) found out that this disorder in which excessive amounts of iron are absorbed through the gut from the diet and deposited in various body organs, particularly the liver, heart, and pancreas.
With time, iron builds up in the organs, and the ultimate effects of this condition include cirrhosis of the liver, diabetes, enlarged heart, cardiac arrhythmias, and heart failure.
They hypothesized that the accumulation of iron in the liver could have deleterious physiological manifestations such as the promotion of lipid peroxidation, an effect which has been studied extensively.
It was said that the number of transformed, premalignant cells in the lungs is exposure-related and reversible. Increased levels of iron and transferrin (i.e., the iron transport protein in serum) in the blood were found in the welders who showed positive reactions to the tumor antigens, which suggested that an increased cancer risk among welders may be associated with the accumulation of iron in susceptible organs.
Health
The human health effects of PCBs were first formally documented in the Yusho and Yucheng incidents. The Yusho incident occurred in Japan in 1968 and involved more than 1,600 individuals ingesting rice oil contaminated with PCBs.
Reported health effects of those exposed included acneform dermatitis, hyperpigmentation of the skin, aches, and pain, peripheral nerve damage, and severe headaches.
The children born to affected mothers showed similar effects, in addition to decreased birth weight and impaired intellectual development. A similar incident occurred in 1979 in Taiwan, where about 2,000 people consumed rice oil contaminated with PCBs. It was called Yucheng, which means ‘oil disease’ in Chinese.
Other effects of PCBs in animals include changes in the immune system, behavioral alterations, and impaired reproduction. PCBs are not known to cause birth defects and few studies on workers who were exposed to PCBs for a long time indicated that PCBs were associated with certain kinds of cancer in humans.
Epidemiological studies of workers involved in the production and use of PCBs have reported increased mortality from cancers of liver, gallbladder, and biliary tract, gastrointestinal tract, malignant melanoma, lung, and brain cancers.
The results of some studies indicate that PCBs containing 60% chlorine by weight are carcinogenic in animals. The most likely way infants will be exposed to PCBs is from breast milk.
Trans placental transfers of PCBs were also reported. In most cases, the benefits of breastfeeding outweigh any risks from exposure to PCBs in mother’s milk. In vitro studies, it was revealed that rats that ate food containing high levels of PCBs for two years developed liver cancer, and therefore, PCBs have been classified as probably carcinogenic and carcinogenic to humans (Group 1) by the Environmental Protection Agency (EPA) of USA and International Agency for Research on Cancer (IARC).
Potential ecological impact
Laboratory and field studies with wildlife have demonstrated a causal link between adverse health effects and PCB exposure. Chronic toxicity has been observed in fish, birds, and mammals and the impacts include developmental effects, reproductive failure, liver damage, cancer, wasting syndrome, and death. There was also some evidence that PCBs can affect the immune system of birds and marine mammals through diet.
Ecological exposure to PCBs is primarily an issue of bioaccumulation resulting in chronic effects rather than direct toxicity. PCBs bio-accumulate in biota by both bio-concentrating (being absorbed from water and accumulated in tissue to concentrations greater than those found in surrounding water) and biomagnifying (increasing in tissue concentrations as they go up the food chain through two or more trophic levels).
At most contaminated sites, PCBs are predominantly bound to particles or strongly associated with an organic fraction. Therefore, aquatic organisms are exposed to a combination of dissolved, sediment-associated, and food-associated PCBs.
However, in terrestrial ecosystems, lower trophic level organisms are exposed to PCBs primarily through ingestion of soil and prey, although dermal absorption and inhalation might be important routes of exposure for certain species.
As a result, organisms at the top of the food chain are generally at the greatest risk of adverse effects due to exposure to PCBs, and the ultimate effect is loss or decline of aquatic and terrestrial biodiversity.
Reducing the risk of exposure
You and your children may be exposed to PCBs by eating contaminated fish or wildlife caught from contaminated locations. Children should be told not play with old appliances, electrical equipment, or transformers, since they may contain PCBs.
Children should be discouraged from playing in the dirt near hazardous waste sites and in areas where there was a transformer fire.
Children should also be discouraged from eating dirt inadvertently and putting dirty hands, toys or other objects in their mouths, and should wash hands frequently. Further, the small scale welders should refrain from using coolant oil contaminated with PCBs.
Moreover, they should use protective gloves and clothing in any case.
The EPA has set a limit of 0.0005 milligrams of PCBs per liter of drinking water (0.0005 mg/L).
The Food and Drug Administration (FDA) in USA requires that infant foods, eggs, milk and other dairy products, fish and shellfish, poultry and red meat contain no more than 0.2-3 parts of PCBs per million parts (0.2-3 ppm) of food.
The writer, a Zoology Professor, is Head Department of Zoology, Faculty of Applied Sciences, University of Sri Jayewardenepura.