Summary
PCBs are evidently a great threat to the environment in general. Concerns about the toxicity of PCBs are very significant owing to the fact that PCBs have been identified as ubiquitous environmental pollutants. As discussed herewith, PCBs have been found to be virtually everywhere in the environment. This is perilous to the human health, as well as the environment. The issue of PCBs is, therefore, something worth considering.
As a means to control the use of this dangerous compound, among the other methods discussed above, PCBs’ use has been prohibited in the USA and in virtually all countries. Nevertheless, PCBs are yet to be brought under absolute control since they are still allowed by the PCB regulations to be used in electrical equipment, specifically as dialectric fluids and as contaminants in these fluids.
Industries with large distribution of power are the chief producers of PCBs to the environment, whereby PCBs are released by accidental spillage or careless abandonment of PCB equipment in the environment. This implies that PCBs can still be in the environment, and since they are hard to biodegrade they will keep on accumulating in the environment while exposing inhabitants to health risks.
The greatest danger is if they cause water pollution because there is no efficient solution to handle this pollutant yet. Portals of entry to human body include almost all organs, and once in the body they can wreak insurmountable havoc.
Introduction
Persistent organic pollutants (POPs) are organic materials that emanate from human activities. These organic materials are not easily broken down by chemicals, sunlight, or even biological mechanisms. Due to this fact, POPs readily bioaccumulate in the environment. POPs are a threat to the health of humans and the environment in general due to their toxic characteristics (Alcock 16).
Many compounds can be classified under POPs; “aldrin, dieldrin and endrin, the chlordane, and chlordecone, DDT, mirex, heptachlor, the hexabromobiphenyl, hexachlorocyclohexanes, and hexachlorobenzene.” Also inclusive are the polyaromatic hydrocarbons, polychlorinated biphenyls (PCBs), the polychlorinated dibenzodioxins, dibenzofurans, as well as toxaphene (UNECE 3). This paper focuses on PCBs (polychlorinated biphenyls).
PCBs are found in virtually all partitions of the global system, at least in trace amounts. They can be found in tissues of humans in many parts of the globe, including areas that do not produce or use PCBs. These organic components do not naturally occur in the environment, but they are aromatic chemicals (Alcock 147). PBCs have low solubility in water and possess semi-volatility, as well as resistance to degradation.
These characteristics predispose the PCBs to persistence, as well as long-range transport in the environment. Organisms, due to the physicochemical properties as well as metabolites of the PCBs, absorb these compounds readily. They are capable of bioconcentrating and biomagnifying in typical conditions of the environment.
History
A PCB-like chemical was first discovered in 1865 as a product of coal, and then in 1881 PCB was synthesized in the laboratory by German chemists. Then, PCB was considered as a safer cooling, as well as an insulating fluid compared to standard mineral oil since PCB was less inflammable. It was used in various electronic gadgets to improve resistance to fire and heat of PVC coating, which were used traditionally (Riseborough and Brodine 249).
Mosanto and Swan Chemical companies took over PCB production in 1929. Owing to PCB toxicity, numerous medical cases were received between 1936 and 1937. Nevertheless, its manufacture was continued with limited restraints until 1970s when an effective ban on PCBs was introduced. Mosanto, the sole North American PCB producer, continued to market PCBs in the name Aroclor up to 1977 (Kaley et al. 11).
Transport and transformations in the environment
PCBs gain entry into the environment from sources like leaks and spills from devices that contain PCB. They may also enter the environment via global transport. The haze of the Arctic that is seen all through the circumpolar world comprises of PCBs and other POPs. PCBs demonstrate low pressure of vapor, making them easily deposit in the soil, water and living organisms as they target the organic sections of these environments.
Despite the hydrophobicity of PCBs, they are absorbed in oceans in substantial quantities owing to the immense volume of oceanic waters. It is, however, vital to note that PCBs are found in the atmosphere in virtually all regions in minute quantities.
The primary path for PCB global transport is the atmosphere, though the hydrosphere is the chief reservoir. PCB concentrations in rural areas are in pictograms per metre3, higher in urban and semi urban areas, but highest in city centers (1ng/m3). Concentrations of, “up to 35ng/m3 have been observed in some houses in the US (10 times higher than the guideline limit of EPA, which is 3.4ng/m3)” (Rudel, Seryak, and Brody 72).
Recent research suggests that ventilation of indoor air contaminated by PCB is the chief source of atmospheric PCB contamination. Previously PCBs volatilization in the soil was considered to be the main source (Jamshidi et al. 2156). Degradation of PCBs can occur in the atmosphere, whereby photolysis process leads to breakdown of the C-Cl bond.
Radicals of hydroxyl may also lead to atmospheric degradation of PCBs. In the biosphere, bacteria, as well as eukaryotes can degrade PCBs. The rate of the reaction is determined by the position of chlorine atoms in the said molecule, as well as the numbers of atoms available. Therefore, PCBs that are either para- or meta-substituted are biodegraded faster in comparison to substituted congeners.
Dechlorination of PCBs is done by the aid of a process called reductive dechlorination, while the process of oxidation is done using dioxygenase enzyme. Eukaryotes utilize the cytochrome p450 to oxidize PCBs.
Laws and regulations in Canada and other parts
The PCBs in Canada are controlled under the Canadian Environmental Protection Act, 1999 (CEPA 1999). In 2008, the law that regulated storage of PCBs and chlorobiphenol was revoked. The PCB 2008 regulations replaced this law. In addition, the ‘CEPA’s Export and Import of Hazardous Waste Regulations’ also regulate PCBs.
The new rules forbid production, use and trade in PCBs. The regulations limit the use of PCBs to particular products that had already been manufactured/imported into Canada in the late 1970s and instituted restrictions on the environmental release of PCBs and deadlines for finishing the use of the remaining PCB products with concentrations of 50mg/kg or more.
Use of products with 500mg/kg or more was abolished by December 31, 2009. Canada has both, “federal, as well as provincial regulatory requirements regarding the storage facilities addressing safety, prevention of pollution and waste destruction tracking” (O’Reilly and Yarto 10). The regulations (2008) restrict PCBs to a period of one year in maximum (O’Reilly and Yarto 10).
Mexico, under the ‘Sound Management of Chemical (SMOC) of CEC’, agreed with Canada and America formulate NARAP to oversee PCBs. Mexico was, thus, provoked to come up with its first inventory of PCBs, and adopt the regulatory NOM-133-SERMART-2000 in 2001 December.
Details on environmental protection as regards PCB handling and targets of elimination have been clearly elaborated in the document. In addition, it specifies maximum environmental limits of emission of PCB that are acceptable (O’Reilly and Yarto 13).
In the US, PCBs are regulated at the federal level. A section of the Federal Toxic Substances Control Act (TSCA) is devoted to PCBs. A substantial amount of coverage on PBC regulations has been done in the Code of Federal Regulations.
The new rules barred production, use and trade in PCBs, unless in very restricted situations. The Environmental Protection Agency (EPA) also tackles regulatory and non-regulatory strategies to manage and eradicate PCB (O’Reilly and Yarto 19).
Air pollution and the current situation in North America
PCBs have been detected everywhere in the atmosphere where PCBs have been looked for in North America, In urban and industrial centers or even near these places, PCBs concentrations are always recorded as highest; 2600 picograms/m3 concentration was reported in 2004 in Chicago (Sun et al. 1131).
Areas that are quite far from urban centers have recorded as low as 20-30pg/m3 in concentration of PBCs. The Canadian arctic is one example of such an area. Most of the PCB in the atmosphere is predominantly in vapor phase. Recent reports indicate that PCB concentrations in vapor phase are on the decline in most sites on the Great Lakes.
Trends of decreasing PCB concentration (faster than in Great Lakes) were reported between 1993 and 2001 (Hung et al. 123). Between the year 2002 and 2004, Southern Mexico registered as low as 34-213pg/m3 of PCB. In 2006, PCB levels in air in Mexico City Metropolitan ranged from 100-840 pg/m3 (indoor) and 87-660 pg/m3 (outdoor) (Sun et al. 1135).
How people get exposure to PCB
People are unavoidable exposed to minute quantities of PCBs in the environment, foods, as well as water. This implies that all Canadians harbor certain concentrations of PBCs in the body system, despite the fact that the quantities are too low to be termed as a health risk. People consuming large amounts of fish, wildlife and marine mammals are at risk of more dietary PCB exposure.
Servicemen dealing with electrical equipment, store keepers and transporters of PCB materials can also come into contact with PCBs. People can come into contact with PCBs that are accidentally leaked into the atmosphere, such as through PCB fires.
Heath effects
Research has revealed that wildlife has experienced certain diseases and malformations as a result of contact with PCBs. Abnormalities in animals are an early warning to humans. Abnormalities in behavior and birth defects have been reported in mammals, fish and birds in and around the Great Lakes (Ritter, Solomon, and Forget 79).
Most adverse health effects include, “chloracne (severe form of acne), upper eyelid swelling, and nail and skin discoloring, arm and leg numbness, weakness, spasms of muscles, bronchitis (chronic), and nervous system problems” (Alcock 153).
International Agency for Research Cancer (IARC) found out that high PCB concentration exposure for a long-term can been associated with cancer (Wolff et al. 649).
The toxicity of PCBs starting manifesting in the 1970s upon discovery of withered seabird corpses in beaches. Monkeys exposed to PCB have been found to exhibit low birth weights, increased skin pigment, reduced lymph and thymus, and gastric mucosa enlargement and reduced bone marrow.
PCBs have also been found to manifest toxic, as well as cancerous effects since they can interfere with body hormones; they can inhibit and behave like estradiol. Mimicry of compounds of estrogen nourishes breast cancer cells that are estrogen-dependent (Health Canada 1-3).
Management and destruction PCB
Traditional methods included:
- System of landfill cap and deep injection of well- used to cover waste materials to avoid contact with environment and manage human and ecological risks at the site of remediation.
- High temperature incineration- it involves PCBs destruction by high temperatures (870-12000C) ex situ to treat polluted soil.
- Cement kilns- highly destroy hazardous wastes by high kiln temperature and long residence time (Rahuman et al. 13-16).
Emerging innovations include:
- Super dangerous oxidation- uses solubility characteristics of supercritical water to destroy compounds.
- Electrochemical oxidation- converts organic wastes to streams that can be environmentally acceptable.
- Technology of solvated electron- it neutralizes halogenated like those containing chlorine
- Reaction of chemical reduction- reduces organic compounds by hydrogen at 850°C or above.
- Dehalogenation process- removes halogens from chemical contaminants via hydrogen or reduction of a radical with hydrogen donor (Rahuman et al. 16-22).
Conclusion
The fact that PCBs products are still in use (though restricted) presents opportunities for illegal and inappropriate disposal of these wastes. There is an increase in the burden of PCBs on the environment, posing unforeseeable repercussions in the future.
Unfortunately, elimination of PCBs is not imminent, unless prompt action is taken to increase the rate and efficiency of phasing out these PCBs. The government should ensure strict adherence to the PCBs regulations and international interventions, collaborations, and agreements to eliminate PCB.
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