polychlorinated biphenyls

Review Papers Acta Toxicologica 2007;15(2):83–93

Magdalena Urbaniak1,2

POLYCHLORINATED BIPHENYLS: SOURCES, DISTRIBUTION AND TRANSFORMATION IN THE ENVIRONMENT — A LITERATURE REVIEW International Institute of Polish Academy of Sciences 1

European Regional Centre for Ecohydrology under the auspices of UNESCO, Łódź, Poland 2

University of Łódź, Department of Applied Ecology, Łódź, Poland

ABSTRACT Over the recent few decades, contamination with persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), has spread all over the world, as evidenced by their detection in a wide range of the environmental media and biota. PCBs are found in the group of the most persistent chemicals. Their physico-chemical properties, such as thermal stability, low flammability and high permittivity, predispose them to have been widely used over the recent 50 years in many industrial applications. These properties have also led to their persistence and accumulation in the environment and biomagnification throughout the food chain. They are found in many compartments of the environment, especially in organisms that are at the top of the chain and may accumulate their significant amounts. Establishing the source of pollutants, their emissions and residues are first steps toward reducing their levels in the environment. Another step is to consider the ability to degrade PCBs by biological or physico-chemical transformation. The first group of degradation includes the anaerobic, aerobic and sequential anaerobic-aerobic transformations. The photochemical and thermal degradation can be classified into the second group. Application of these methods can minimize the risk of the PCB effect. Key words: polychlorinated biphenyls, biodegradation, photochemical degradation, thermal degradation Received for publication: October 22, 2007 Approved for publication: November 28, 2007

Address for correspondence: Magdalena Urbaniak International Institute of Polish Academy of Sciences, European Regional Centre for Ecohydrology under the auspices of UNESCO Tylna 3, 90-364 Łódź, Poland Phone: +48 42 681-70-07, fax: +48 42 681-30-69 E-mail: [email protected]

© Copyright by the Polish Society of Toxicology

84

M. Urbaniak

INTRODUCTION Polychlorinated biphenyls (PCBs) are an important group of substances that were manufactured in large amounts for numerous industrial applications between the 1930s and 1970s and dispersed in the environment mainly as a result of industrial uses [1–3]. Having evidenced their accumulation in the environment and their toxic effects on humans and animals, the manufacture and use of PCBs were banned in the 1970s [4–6]. Due to their liphoplilic character they can bioaccumulate in cells and pass up through the food chain and remain in soils, sediments and water bodies for several years (Tab.1). The environmental persistence of PCBs may result primarily from low ability of natural aquatic and soil biota to metabolize these compounds at a considerable rate. In the 1970–80s, many countries imposed a strict control over the use and release of PCBs. Thus, their effect on the environment has decreased significantly; nevertheless a release of PCBs from contaminated reservoirs, such as lakes and coastal sediments still exists [4–6]. Recent surveys have shown that large amounts of persistent organochlorines can be released into the atmosphere from contaminated sites and redistributed on a global scale [7]. Many of them decompose slowly and exert toxic effects on plants and animals, and consequently contribute to extensive environmental degradation. Despite many years of measuring their levels in numerous environmental compartments, quantitative information on emissions of PCBs remains limited and subject to significant uncertainties. A lack of complete and accurate emission data for PCBs is considered by

many scientists as a key knowledge gap in the understanding of the overall environmental distribution and fate of PCBs [7]. The aim of this work was to summarise and synthesize the data, which have been gathered on PCBs, as well as on the possibilities of reducing their concentrations in the environment.

CHEMISTRY OF POLICHLORINATED BIPHENYLS General physico-chemical properties Polychlorinated biphenyls are commercial products prepared industrially by the catalytic chlorination of biphenyl with anhydrous chlorine in the presence of iron fillings or ferric chloride as a catalyst. The purified product is a complex mixture of chlorobiphenyls containing from 18 to 79% of chlorine. Their empirical formula is as follows: C12H10 –xCl x (Fig. 1). There are theoretically 209 possible polychlorinated biphenyls,

Cly

Clx

Fig. 1. Biphenyl structure [51].

differing from each other by the level of chlorination and substitution position. In general, the most common isomers are those with an equal number of chlorine atoms on both rings or differ in only one chlorine atom between the rings [8].

Table 1. T1/2 for selected PCBs [52] Degree of chlorination 1 2 3 4 5 6 7 8 9 10

Air 1 week 1 week 3 weeks 2 months 2 months 8 months 8 months 2 years 2 years 6 years


Water 8 months 8 months 2 years 6 years 6 years 6 years 6 years 6 years 6 years 6 years

Soil 2 years 6 years 6 years 6 years 6 years 6 years 6 years 6 years 6 years 6 years

Sediment 2 years 2 years 6 years 6 years 6 years 6 years 6 years 6 years 6 years 6 years

Acta Toxicologica 2007;15(2):83–93

85

POLYCHLORINATED BIPHENYLS IN THE ENVIRONMENT

PCBs have been produced under several trade names, e.g., Clophen (Bayer, Germany), Aroclor (Monsanto, USA), Kanechlor (Kanegafuchi, Japan), Santothrem (Mitsubishi, Japan), Phenoclor and Pyralene (Prodolec, France) (Tab. 2). Table 2. Major trade names of PCBs Apirolio Areclor Aroclor Arubren Asbestol Askarel Bakola Biclor Chlorextol Chlorinol Chlorphen Clophen Delor

Diaclor Duconol Dykanol Elemex Euracel Fenchlor Hivar Hydol Inclor Iterteen Kennechlor Montar Nepolin

No-Flamol Pydraul Pyralene Pyranol Pyroclor Phenoclor Saf-T-Khul Santotherm Santovac Siclonyl Solvol Sovol Therminol

Commercial PCBs are complex mixtures of 30–60 congeners, which are the major PCB components of most environmental extracts. Each individual compound shows a unique combination of physico-chemical and biological properties dependent on the degree of chlorination. Lower chlorinated commercially produced PCBs (mono-, di-, tri-, tetra-) range from highly mobile liquids to oils. Penthachlorobiphenyls are heavy, while viscous oils and the most chlorinated PCBs are resins through greases to waxy substances. Most individual chlorobiphenyls are solids at room temperature. They possess a high flash point (170– 380°C), low electric conductivity and extremely high thermal and chemical resistance (Tab. 3).

Solubility Solubility of PCBs in water and in organic solvents, such as lipids, influences their transport and persistence in the environment. PCBs solubility in water is very low and decreases with increasing degree of chlorination. Water solubility for Aroclors ranges from 0.000004 to 7.48 m/l. Solubility in fat and oils is extremely high. Individual chlorobiphenyls vary in their solubility from 6 ppm for monochlorobiphenl to 0.007 ppm for octachlorobiphenyl. Decachlorobiphenyl is about twice as soluble as octachlorobiphenyl. The solubility of the compound plays an essential role in its degradation. Compounds with high aqueous solubility can be easier degraded by microorganisms than those with low solubility (highly chlorinated congeners are weakly soluble in water, which causes their resistance to biodegradation) [9]. Vapour pressure and vaporisation Vapour pressure of PCBs depends on the chlorination degree and decreases with increasing chlorination. The decrease of vaporisation rates by about 200 times was observed for commercially produced PCBs under trade name Aroclor. Less chlorinated Aroclor 1221, consisting of mono- and dichlorobiphenyls, shows a vaporisation rate of 0.00174 g/cm 2/h, whereas Aroclor 1260, consisting of penta-, hexa-, hepta-, and octachlorobiphenyls, of 0.000009 g/cm2/h. Haque et al. [10,11] investigated two sites in Canada and reported that about 60% of Aroclor 1254 in sand in Ottawa was reduced by vaporisation in one month, whereas no significant reduction was observed in Woodburn soil in the same period. The role of various components of soils and sediments, such as surface area, type of clay, content of organic matter and pH, which

Table 3. Physico-chemical properties of selected Aroclors [53] Aroclor

Water solubility

Vapour pressure

compound

[mg/l] 25°C

25°C

1016

0.4200

4.0×10–4

1.33

Clear oil

325–356

1221

0.5900

6.7×10–3

1.15

Clear oil

275–320

1232

0.4500

4.1×10–3

1.24

Clear oil

290–325

1242

0.2400

4.1×10–3

1.35

Clear oil

325–366

1248

0.0540

4.9×10–4

1.41

Clear oil

340–375

1254

0.0210

7.7×10–5

1.50

Light, yellow, viscous oil

365–390

1260

0.0027

4.0×10–5

1.58

Light, yellow, viscous oil

385–420


Density

Appearance

[g/cm ] 25°C 3

Boiling point [°C]


86

M. Urbaniak

influence PCB vaporisation from the surface, is poorly understood. The vapour pressure of less chlorinated biphenyls showed a greater loss, in contrast to the more chlorinated biphenyls, which are more stable in soil. In addition, the studies show that temperature-dependence of vapour pressure and in consequence the rate of evaporation, exert an effect on PCB concentration in the atmosphere and the distribution of PCB congeners in the global scale. Temperature-dependence of air concentrations appears to be most pronounced for more chlorinated congeners and to increase with the degree of chlorination [12]. Sorption reaction Sorption reaction influences the transport and fate of PCBs in aquatic systems and their partitioning in different compartments of the environment. Sorption rate increases with increasing chlorination of chlorobiphenyl, surface area and organic carbon content of the sorbent. PCBs in environmental samples can be greatly reduced by sorption on the soil and sediment surface. Haque and Schmedding [10,11] reported that sorption of different sorbents (sand, soil, clay and humic acids) occurred in the following order: hexa- > tetra- > dichlorobiphenyls. Other researchers found that PCB sorption by sediments and soils is related to their total organic carbon. These correlations suggest that PCB sorption of low aqueous solubility is due to solute partitioning in the organic matter. For that reason, partitioning of PCBs between organic matter of sediments, soils and water correlates with its partition coefficients between water and immiscible solvent, such as n-octanol.

USES OF POLYCHLORINATED BIPHENYLS Polychlorinated biphenyls are ones of the most stable organic compounds with low dielectric constant, high heat capacity, chemical inertness, non-flammability, high electrical resistivity and low acute toxicity, which render them ideal for industrial applications. Commercial PCBs have been produced and used in many countries, including the United States, Russia, Japan, France, and Czech Republic (former Czechoslovakia). Due to their unusual versatility PCBs have been widely used in a wide range of industrial applications, such as dielectric fluids, heat transfer fluids, hydraulic fluids, flame retardants, solvent extenders and organic diluents. The global official use of PCBs ranged from 1.2 to 1.5 million tonnes, but it is recognised that this value is underestimated relative to the true value due to unknown and illegal productions. Fielder [13] reported that since the 1930s, near 2.0 million tonnes have been produced and used worldwide. Holoubek [14] assumed that this amount was about 1.2 million tonnes globally. Brevik et al. [15] estimated that production of PCBs during the peak in the 1970s averaged 76 thousand tonnes per year. The estimated amounts of produced PCB between 1955–1982 are given in Table 4 [16].

SOURCES OF POLYCHLORINATED BIPHENYLS Natural sources of PCBs are not known. Nevertheless PCBs persist in the environment and are found in the air, water, soil, and food.

Table 4. Production of PCBs in selected countries [16,5] Period

France

Germany

Italy

Japan

Spain

UK

USA

1955–1959

7085

7 427

520

3 960

150

2 042

6 800

1960–1964

14 401

14 854

1 920

10 530

1 289

10 215

94 500

1965–1969

16 975

25 466

4 430

24 750

4 296

22 973

166 300

1970–1974

25 759

34 424

7 195

19 879

9 433

22 017

114 000

1975–1979

28 141

34 072

8 076

0

8 829

9 501

32 900

1980

6 419

7 309

1 388

0

1 131

0

0

1982

n.a.

n.a.

2 482

n.a.

2 354

n.a.

n.a.

n.a. — not applicable.




Before the mid 1970s, PCBs were used in a wide range of applications, including the following: — closed uses — PCBs used in the manufacture of selected electrical equipment, including hydraulic and heat transfer fluids, vacuum pumps, transformers and capacitors [12]; — open uses — PCBs used in a diverse range of products, such as plasticizer, carbonless-copy paper, in covering and coating applications (varnishes, paints), as sealants in building materials, oils, laminating and impregnating agents, adhesives in cement and plaster and as pesticides and herbicides. The open use of PCBs was banned in the 1970s; however, some products, such as building sealants are still used due to their properties and can still contaminate the environment; — industrial and non-industrial combustion processes — PCBs can be produced during the processes of municipal waste combustion; hazardous waste and medical waste incineration account for a significant portion of PCBs emitted to the air.

DISTRIBUTION OF POLYCHLORINATED BIPHENYLS IN THE ENVIRONMENT Since the 1970s many of PCBs residues have entered other components of the environment from sealed older existing equipment, as well as from natural sources of PCBs, such as atmospheric, aquatic and soil systems, or as a result of inadequate elimination by waste incineration. The atmosphere, owing to its dynamic character, contains a relatively low percentage of PCBs, however, it is also one of the most common pathways of PCB transTable 5. Concentrations of PCBs in the environment [54] Environment compartment Atmospheric air Water Sediments Plankton Invertebrates Fishes Bird eggs Humans

Concentration 0.1–20 ng/m3 0.001–908 ng/l 1.1–6 000 ng/g s.m 10–20 000 ng/g 10–10 000 ng/g 10–25 000 ng/g 100–500 000 ng/g 100–10 000 ng/g


87

portation. Atmospheric deposition is probably responsible for the global dispersion of PCBs in the environment. The study of Duinker and Bouchertall [17] shows that low chlorinated PCBs are dominant in filtered air, while congeners with a high degree of chlorination are observed mostly in aerosols and rainfall. Mono- and dichlorobiphenyls are usually found in the gas phase and due to low water solubility are not washed out with rainwater from the atmosphere. Higher chlorinated biphenyls are adsorbed to particulates, and thus can be removed from the atmosphere by capturing aerosols in rain drops. These two effects result in a relative accumulation of the lower chlorinated PCBs in the atmosphere [17]. Nevertheless the above statements concerning atmospheric burdens and fluxes can greatly influence the total amount of PCBs in the environment and are considered as a major input of PCBs to water bodies. The atmosphere is the conduit through which PCBs, as well as other POPs can move from atmospheric emission sources via deposition to terrestrial and aquatic ecosystems [18]. There are three major routs of atmospheric PCB input: wet deposition, such as rain and snow, dry deposition of fine and coarse particles, and also gaseous air-water exchange [19–21]. PCBs can undergo long range atmospheric transport, moving from source regions to more remote locations. For that reason, PCBs can be detected in the biota from different regions of the world, where they have been neither used or produced. For example, Braune et al. [22] showed that the concentration of PCBs in char muscle from two locations in Labrador and three locations in Nunavik ranged from 10 to 31 ng/g ww. The same study presented PCB concentrations in Geenland cod of 0.89 ng/g ww, Arctic cod 3.73 ng/g ww, Greenland halibut 11.1 ng/g ww, Greenland shark 2000 ng/g ww and in Arctic char of 30.8 ng/g ww. Weber and Goerke [23] revealed that PCB-153 concentrations in three fish species of different feeding types from the area of Elephant Island in the Antarctic were within the range of 0.4–2 ng/g lipid. The authors also suggested that between 1987 and 1996, the levels of PCB-153 showed a significant increase in the benthos feeder and the fish feeder and low increase in the krill feeder. The study of Luke et al. [24] conducted on the Antarctic and subantarctic seabirds showed PCB concentration level lower than 0.1 μg/g PCBs (1260). The values presented by the above mentioned authors indicate that the environmental levels of PCB contami-


88

M. Urbaniak

nants in the biotypes of these species are low, and thus should not be regarded as a significant threat. The process of PCB transport comprises three steps: first, emission of PCBs to the atmosphere by combustion, incineration, volatilisation from the source region; second, transport through the atmosphere to a more remote regions [25–28] and the third step is the deposition (dry or wet) of PCBs. Sometimes the re-emission of PCBs from environmental compartments (soil, water, vegetation) can occur. Offenberg et al. [29] hypothesized that emission of PCBs into the coastal atmosphere from industrial areas leads to increased depositional fluxes. The areas of most concern include the open oceans, which contain the major amounts of total atmospheric PCBs. The terrestrial environment, except for high industrialized areas, have relatively small contribution to total amount of PCBs. However, equipment dumps, landfills, sewage sludge and PCB-coated silos represent large PCB reservoirs. They frequently find a way to contaminate the terrestrial area and groundwater [30]. In water, PCBs can be adsorbed on sediments and organic matter, which contributes to the decrease in the volatilisation rate; nevertheless the PCBs can move from sediment to water by desorption, bioturbation, gas convection and erosion, and then may be transported and enriched in the surface micro-layer or transported to the air. On the basis of their water solubility and n-octanol-water partition coefficients, the lower chlorinated PCB congeners are sorbed less strongly than the higher chlorinated isomers. The low solubility and strong adsorption of PCBs on soil particles limit their leaching in soil. Lower chlorinated PCBs tend to leach more than those highly chlorinated. Contaminated lake sediments can release some amounts of PCBs into the food chain during water mixing. On the other hand, sedimentation can greatly reduce the concentration of PCBs in water by binding PCB congeners to particulates. The higher sedimentation rates accompanied by sediment burial in eutrophic lakes have been suggested as one of the mechanisms responsible for this negative relationship. Studies in 19 temperate lakes, located in the southern part of Sweden, demonstrated a negative relationship between lake trophy and PCB concentration. The concentration of PCBs in aquatic organisms decreased with the trophic status of lakes, measured as a total phosphorus concentration or plankton biomass. Due to greater


amounts of settling organic matter the microbial degradation in shallow eutrophic lakes is insufficient to mineralise the entire pool of settling organic carbon. Therefore, liphoplilic PCBs associated with the settling organic matter may not be released back to water but accumulated in the sediment [31]. On the other hand, the turnover of organic matter in oligothrophic lakes is more efficient, hence PCBs associated with settling particles are recycled back to the water. Polychlorinated biphenyls deposited in sediments may directly be taken up from the sediment to the food chain by benthic organisms. To describe this process the biota-sediment accumulation factor (BSAF) is used. The study carried out by Moermond et al. [32] can be listed here as an example. These authors reported that BSAFs in flood plain lakes situated on the southern side of the Rhine River in the Netherlands ranged from 0.01 to 1.6 for Oligochaeta, with average value of 0.39, and 0.32 for mixed invertebrates (the composition of invertebrates without Oligochaeta). Maul et al. [33] reported BSAFs for male and female Chironomus sp. in the range of 12.19 and 0.95, respectively, BSAFs for tree swallows nestlings was 2.67. In addition, the highest BSAF was noted for the mono-ortho-substituted congener 118, whereas PCB-56 had the lowest value. It could be stated that PCBs are chemicals classified as persistent, bioaccumulative, toxic substances (PTBs) according to European Union (EU) and Global Harmonized System (GHS). PCBs present in water tend to bioaccumulate in food chain through phytoplankton, zooplankton and other biota. Aquatic invertebrates assume an important role in the cycling of PCBs within and between ecosystems. Evans et al. [34] reported that Mysid crustaceans from Lake Michigan have low assimilation efficiency for PCBs and high efficiency for faecal excretion of ingested PCBs, which in consequence reach the sediments in PCBs. Moreover, Mysid, by migrating vertically in water column, may transport PCBs into the surface region. Fox et al. [35] found a positive correlation between PCB levels in Oligochaeta and sediments. Also the uptake of PCBs from sediments by larvae of Chironomidae was directly related to the concentration of PCBs in the sediment. Chironomidae can also transfer PCBs from the aquatic to the terrestrial environment when larvae metamorphose to adults. The rate of this transport was estimated at 20 µg/m 2/year of PCBs [36].



TRANSFORMATION OF POLYCHLORINATED BIPHENYLS Transformation of PCBs is a critical event determining their fate and persistence in the environment. The effectiveness of degradation rates varies, depending on the conditions present in the environment, and comprises the degree of biphenyl chlorination; position of chlorine atoms in the biphenyl nucleus; species of microorganisms, their activity and in-between interactions; the structure of a given PCB compound; the presence of substituents and their position in the molecule; the presence of toxic or inhibitory substances; solubility, temperature, pH, light, and concentration of the pollutant [7–9]. The degradation of PCBs is classified in two section, biological transformation through the activity of microorganisms and physico-chemical transformation. The former includes the anaerobic, aerobic and sequential anaerobic-aerobic transformation. The photochemical and thermal degradation can be classified into the latter one. Biological transformation Biodegradation depends on the enzymes produced by microorganisms, which modify toxic compounds into less toxic forms. Biological degradation can be carried on as a mineralization, where microorganisms use the organic compound as a source of carbon and energy, or as co-metabolism, where organisms need other sources of carbon and energy and transformation of pollutants occurs as a concurrent process. Products of this process can be further mineralized, otherwise incomplete degradation occurs, leading to the formation and accumulation of metabolites more toxic than parent substrates. The use of anaerobic and aerobic microorganisms is the only known process to degrade PCBs in soil and aquatic systems, leading to the removal of chlorine atoms from the biphenyl molecule and theoretically giving CO2, chlorine and water [9,37]. Anaerobic microorganisms Anaerobic microorganisms are well adapted to pollutants with a high carbon concentration due to diffusional limitation of oxygen. Anaerobic transformation of PCBs includes reductive dehalogenation using PCBs as an electron acceptor. During this process a substituent chlorine atom is replaced with a hydrogen atom. Reductive dehalogenation occurs in soils and sediments, where


89

different microorganisms possessing dehalogenation enzymes and responsible for dechlorination and dehalogenation processes do exist. The rate, extent, and route of dechlorination depend on the environmental factors, such as carbon availability, electron donors, presence of electron acceptors other than PCBs, temperature and pH. All of these factors influence the composition of the microorganism community and its activity [7]. The first reported evidence of anaerobical degradations of PCBs was based on the observed modification of the Hudson River and Silver Lakes sediments contaminated by commercially produced PCBs. The increase in low-chlorinated PCBs compared to high-chlorinated congeners, was consistent with reductive dechlorination [38]. Master et al. [39] showed that many commercial PCB mixtures can be reductively dechlorinated under anaerobic conditions, e.g. Aroclor was dechlorinated at rates of 3 μg Cl/g sediment per week. Dechlorination occurs at 12°C and PCB concentrations of 100–1000 ppm. Boyle at al. [40] described the degradation of Aroclor 1242 by three strains: Comamonas testosteroni, Rhodococcus rhodochrus and Psudomonas putida with total losses of 13.8, 19.1 and 24.6%, respectively. In both experiments, the favourite positions for dechlorination were in the following order meta > para > ortho and showed preferences for ’open‘ sites, 2 and 3, indicative of the action of 2,3-dioxygenase enzymes [39,40]. Also Fava et al. [41] reported that dechlorination of Fenclor 54 primarily occurred in the meta- and para-positions, while ortho-subsituted congeners accumulated in the medium. Laboratory experiments showed that microbial degradation of lower chlorinated biphenyls occurs at a faster rate than the higher chlorinated biphenyls. Other study showed an inability of anaerobic microorganisms to degrade the low chlorinated biphenyls. The occurrence of di-ortho- and monoortho-chlorobiphenyls, as well as the biphenyl rings was identified even after a one year incubation [42]. Lower chlorinated congeners produced by dechlorination can be readily degraded by indigenous bacteria, which, in consequence, reduces the potential bioconcentration risk and the exposure to PCBs by conversion to congeners with low bioaccumulation potential in the food chain [27,42]. The lightly chlorinated PCB congeners, produced during the anaerobic dechlorination, may then be substrates for oxidative destruction by aerobic microorganisms, which leads to the production of chlorobenzoic acid, easily degraded by bacteria.


90

M. Urbaniak

Aerobic microorganisms The first data on aerobic degradation of PCBs was reported by Ahmed and Focht [43] in 1973 and the respective study was devoted to degradation of biphenyl and monochlorobiphenyl to chlorobenzoic acid by two species of Achromobacter. Furukawa et al. [44] demonstrated that species of Acinetobacter sp. and Alcaligenes sp. may rapidly adsorb 2,5,2’-trichlorobiphenyl onto the cell surface, then metabolise and release metabolic compounds from the cell. Since then numerous investigations have been focused on the occurrence and distribution of PCB-degrading microorganisms and their capability to biodegrade PCBs. Biphenyl and monochlorobiphenyl are common growth substrates for aerobic bacteria degrading PCBs. The degradation of more chlorinated PCB congeners occurs owing to co-metabolism, where a biphenyl molecule is used as a source of carbon and energy or as a degrading enzymes inductor. Clark et al. [45] reported that Alcaligenes denitrificants and A. odorans can degrade Aroclor 1242 by co-metabolism. Novakova et al. [46] showed the results of the degradation of Delor 103 by Psudomonas sp. P2 and Alcaligenes eutropha. Optimal PCB degradation was obtained by an addition of biphenyl, saccharose, agar or amino acid mixture as a source of sole carbon. The reduction of degradation efficiency was observed after the addition of glycerol or pyruvate. To complete degradation of PCBs by aerobic bacteria, various microbial strains with specific congener preferences are required. The study showed that only less chlorinated PCBs can be degraded, whereas highly chlorinated congeners remain biorefractory to aerobic bacteria. Therefore, highly chlorinated congeners have been found to be reductively dechlorinated under anaerobic conditions through a preferential meta- and para-chlorine removal and production of less chlorinated congeners, which then can be used in aerobic transformations. These results suggest that a complete degradation of PCBs can be achieved by a sequential exposure to anaerobic and aerobic microorganisms [10,47,48].

tion. The primary process in photoreaction is reductive dechlorination, but examples of photo-induced isomerization and condensation of individual chlorobiphenyls have also been reported. The first laboratory experiments on photolysis were conducted with mercury lamps as UV source, with wavelength about 254 nm, which resulted in dechlorination of PCBs. Many studies have been performed with the high energy UV radiation and UV f luorescent lamps simulating sunlight, producing PCBs less chlorinated than the initial material. Higher chlorinated biphenyls undergo photolysis faster than less chlorinated ones. For example, exposure of PCBs at 310 nm reduces about 70% of tetra-, 96% of hexa-, and 99% of octachlorobiphenyl. Experiments with tetrachlorobiphenyls showed that the major products after irradiation at 300 nm are di- and trichlorinated biphenyls [48]. Bunce et al. [49] reported intensified photodegradation with increased irradiation time. Photolysis is one of the major processes, which reduce PCBs in the environment. Bunce at al. [49] estimated the loss of PCBs in natural waters at a magnitude of 10 to 1000 g/Km-2/year. In shallow water bodies at least one chlorine atom from mostly chlorinated PCB molecule is photodegraded per year. Zepp et al. [50] reported that humic acids and suspended materials may induce and accelerate PCB photodegradation.

Physical transformation Photochemical degradation Photolysis of PCBs also depends on the degree of chlorination, position of chlorine atoms in the biphenyl ring, and the solvent used for PCB dissolu-

The presented data show that PCBs can be effectively degraded by using environmental properties, like existing microorganism consortia or enhancement of carbon, oxygen and light availability. Nevertheless most of our knowledge of the degradation of PCBs comes from labo-


Thermal degradation The last group of PCB transformation is thermal degradation leading to complete destruction of toxic substances at temperature above 700°C or production of more toxic substance, such as polychlorinated dibenzofurans and polychlorinated dibenzodioxins at temperature below 700°C. This kind of PCB destruction is well adapted on an industrial scale for safe disposal of PCBs containing waste products [51].

CONCLUSIONS


91


ratory experimental systems conducted on pure cultures of bacteria in laboratory media, containing a single PCB congener or specific UV radiation and temperature. In the natural environment, metabolism of PCBs occurs via complex metabolic networks involving complicated interactions with other contaminants and with various physiological and biological processes. Therefore, there is a need to perform more ’near-to-nature‘ experiments to optimise these processes and thus apply in situ bioremediation.

References 1. Jones KC, de Voogt P. Persistent organic pollutants (POPs): state of the science. Environ Pollut 1999;100:209–21. 2. Wiegel J, Wu Q. Microbial reductive dehalogenation of polichlorinatyted biphenyls. FEMS Microbiol Ecol 2000;32:1–15. 3. Mitten ME, Dress KS, Krochota WG, Ewald FP, de Witi BJ. Chlorocarbons. In: Ettre LS, Snell FD, editors. Encyclopedia of Industrial Chemical Analysis. New York: John Wiley and Sons; 1970. pp. 369–510. 4. Organization for Economic Cooperation and Development

M. Urbaniak

(OECD): Polychlorinated biphenyls their use and control.

POLICHLOROWANE BIFENYLE:

Paris: Environment Directorate; 1971.

Źródła, dystrybucja I transformacja

5. Bletchly JD. Polychlorinated biphenyls. Production, cur-

w środowisku — przegląd literatury

rent use and possible rates of further disposal in OECD

Streszczenie

member countries. In: Barres MC Koeman H, Visser R, editors. Proceedings of PCB seminar. Amsterdam: Ministry

W ciągu ostatnich dekad zanieczyszczenia trwałymi związ-

of Housing, Physical Planning, and Environment; 1984.

kami organicznymi (TZO), takimi jak polichlorowane bife-

6. Hansen LG. Environmental toxicology of polychlorinat-

nyle (PCB), rozprzestrzeniły się na całym świecie. Dowodem

ed biphenyls. In: Safe S, Hutzinger O, editors. Environ-

tego są ich wysokie stężenia notowane w różnych komponen-

mental Toxin Series. New York: Springer-Verlag; 1987.

tach środowiska abiotycznego i biotycznego. Polichlorowane bifenyle są jednymi z najbardziej trwa-

pp. 15–48. 7. Langer P. Persistent organochlorinated pollutants (POPs)

łych związków chemicznych. Ich specyficzne własności fi-

and human thyroid — 2005. Endocr Regul 2005;39:53–68.

zykochemiczne — takie jak stabilność termiczna, niepalność

8. Imamoglu MG, Rayne S, Addison RF. Exponential in-

oraz trwałość — zdecydowały o ich szerokim zastosowaniu

crease of brominated flame retardants, polybrominated

w różnych działach przemysłu w ciągu ostatnich 50 lat. Po-

diphenyl ethers, in the Canadian Arctic from 1981–2000.

wyższe własności zadecydowały również o trwałości i aku-

Environ Sci Technol 2002;36:1886–92.

mulacji tych związków w środowisku oraz biomagnifikacji

9. Borja J, Taleon DM, Auresenia J, Gallardo S. Polychlo-

wzdłuż łańcucha troficznego. Mierzalne poziomy PCB znaj-

rinated biphenyls and their biodegradation. Process Bio-

dowane są w wielu składnikach środowiska, a znaczne ich

chem 2005;40:1999–2013.

ilości akumulują zwłaszcza te organizmy, które znajdują się na szczycie piramidy troficznej.

10. Haque R, Schmedding DW, Freed VH. Aqueous solubility, adsorption, and vapor behavior of polychlorinated biphe-

Ustalenie źródła zanieczyszczenia, w rozumieniu jego

nyls Aroclor 1254. Environ Sci Technol 1974;8(2):139–42.

emisji bezpośredniej oraz emisji z pozostałości PCB, jest

11. Haque R, Schmedding D. Studies on the adsorption of

pierwszym krokiem w kierunku redukcji poziomu tych za-

selected polychlorinated biphenyl isomers on several sur-

nieczyszczeń w środowisku. Drugim etapem jest oszacowa-

faces. J Environ Sci Health B 1976;11(2):129–37.

nie zdolności do ich biologicznej degradacji i transformacji

12. Fielder H. Global and local disposition of PCB. In: Rob-

fizykochemicznej. Do grupy biologicznej degradacji zaliczyć

ertson LW, Hanssen LG, editors. PCBs-Recent Advances

można takie procesy, jak degradacja beztlenowa, tlenowa

in the Environmental Toxicology and Health Effects. Ken-

oraz degradacja sekwencyjna: beztlenowo-tlenowa. Z kolei

tucky: University Press of Kentucky; 2001. pp. 11–5.

w grupie transformacji fizykochemicznych znajduje się de-

13. Holoubek I. Polychlorinated biphenyl (PCB) contaminated

gradacja fotochemiczna oraz termiczna. Wykorzystanie po-

sites worldwide. In: Robertson LW, Hanssen LG, editors.

wyższych metod może w znacznym stopniu przyczynić się

PCBs-Recent Advances in the Environmental Toxicology

do minimalizacji ryzyka związanego z występowaniem PCB

and Health Effects. Kentucky: University Press of Ken-

w środowisku.

tucky; 2001. pp. 17–26.



92

M. Urbaniak

14. Brevik K, Sweetman A, Pacyna J, Jones KC. Towards

27. Wania F, Dugani CB. Assessing the long-range transport

a global historical emission inventory for selected PCB

potential of polybrominated diphenyl ethers: A com-

congeners — a mass balance approach 2 Emissions. Sci

parison of four multimedia models. Environ Toxicol

Total Environ 2002;290:199–224.

Chem 2003;22:1252–61.

15. Falandysz J. Polychlorinated biphenyls in the environment:

28. Offenberg J, Simcik M, Baker J, Eisenreich SJ. The impact

chemistry, analysis, toxicity, concentration and risk assess-

of urban areas on the deposition of air toxics to adjacent

ment. Gdańsk: Gdańsk University Development Founda-

surface waters: A mass budget of PCBs in Lake Michigan

tion (Fundacja Rozwoju Uniwersytetu Gdańskiego);1999

in 1994. Aquatic Sci 2005;67:79–85.

[in Polish].

29. Gevao B, Beg MU, Al-Omair A, Helaleh ZJ. Spatial dis-

16. Duinker JC, Bouchertall F. On the distribution of at-

tribution of polychlorinated biphenyls in coastal marine

mospheric polychlorinated biphenyl congeners between

sediments receiving industrial effluents in Kuwait. Arch

vapor phase, aerosols, and rain. Environ Sci Tech-

Environ Contam Toxicol 2006;50:166–74.

nol 1989;23:57–62. 17. Klecka G, Boethling B, Franklin J, Graham G, Grady L, Howard PH, et al. Evaluation of persistence and long-range transport of organic chemicals in the environment.. Pensacola, Fl: SEATAC Special Publication Series; 2000.

30. Berglund O, Larsson P, Ewald G, Okla L. Influence of trophic status on PCB distribution in lake sediments and biota. Environ Pollut 2001;113:199–210. 31. Moermond IA, Zwolsman JJG, Koelsman AA. Black carbon and ecological factors affect in situbiota to sedi-

18. Lee WJ, Su C-C, Sheu HL, Fan YC, Chao HR, Fang GC.

ment accumulation factors for hydrophobic organic

Monitoring and modeling of PCB dry deposition in urban

compounds in flood plain lakes. Environ Sci Tech-

area. J Hazard Mater 1996;49:57–88.

nol 2005;39:3101–9.

19. Mandalakis M, Stephanou EG. Polychlorinated biphenyls

32. Maul JD, Belden JB, Schwab BA, Whiles MR, Spears B,

associated with fine particles (PM2.5) in the urban environ-

Farris JL, et al. Bioaccumulation and trophic transfer

ment of Chile: concentration levels, and sampling volatil-

of polychlorinated biphenyls by aquatic and terrestrial

ization losses. Environ Toxicol Chem 2002;21(11):2270–5.

insects to tree swallows (Tachicineta bicolor). Environ

20. Teil MJ, Blanchard M, Chevreuil M. Atmospheric deposition of organochlorines (PCBs and pesticides) in northern France. Chemosphere 2004;55:501–14.

Toxicol Chem 2006;25(4):1017–25. 33. Evans MS, Bathelt RW, Rice CP. PCBs and other toxicants in Mysid relicta. Hydrobiologia 1982;93:205–15.

21. Braune BM, Outridge PM, Fisk AT, Muir DCG, Helm PA,

34. Fox ME, Carey JH, Oliver BG. Compartmental distribu-

Hobbs K, et al. Persistent organic pollutants and mercury in

tion of organochlorine contaminants in the Niagara Riv-

marine biota of the Canadian Arctic: An overview of spatial

er and the western basin of Lake Ontario. J Great Lakes

and temporal trends. Sci Total Environ 2005;51(352):4–56.

Res 1983;9:287–94.

22. Weber K, Goerke H. Persistent organic pollutants (POPs)

35. Larsson P. Transport of PCBs from aquatic to terrestrial

in antarctic fish: levels, patterns, changes. Chemo-

environment by emerging Chironomids. Environ Pol-

sphere 2003;53:667–78.

lut 1984;34A:283–9.

23. Luke BG, Johnstone GW, Woehler EJ. Organochlorine

36. Beursknes JEM, Stolterder PBM. Microbial transforma-

pesticides, PCBs and mercury in Antarctic and subantarc-

tion of PCBs in sediments: what can we learn to solve

tic seabirds. Chemosphere 1989;19(12):2007–21.

practical problems? Water Sci Technol 1995;31(8):99–107.

24. Beyer A, Mackay D, Matthies M, Wania F, Webster E. As-

37. Brown JR, Bedard DL, Brennan MJ, Carnahan JC, Feng H,

sessing long-range transport potential of persistent organic

Wagner RE. Polychlorinated biphenyl dechlorination

pollutants. Environ Sci Technol 2000;34:699–703.

in aquatic sediments. Science 1987;236:709–12.

25. Omamoglu I, Li K, Christiansen ER. Modelling polychlo-

38. Master ER, Lai VW, Kuipers B, Cullen WR, Mohn WW.

rinated biphenyl congener patterns and dechlorination

Sequential anaerobic-aerobic treatment of soil contami-

in dated sediments from the Astabula River, Ohio, USA.

nated by weathered Aroclor 1260. Environ Sci Tech-

Environ Toxicol Chem 2002;21(11):2283–91.

nol 2002;36(1):100–3.

26. Wania F. Assessing the potential of persistent organic

39. Boyle AW, Silvin CJ, Hassett JP, Nakas JP, Tanenbaum SW.

chemicals for long-range transport and accumulation

Bacterial PCB biodegradation. Biodegradation 1992;3

in polar regions. Environ Sci Technol 2003;37:1344–51.

(2–3):285–98.



93


40. Fava F, di Gioia D, Cinti S, Marchetti L, Quattroni G. Deg-

48. Bunce NJ, Kumar Y, Brownlee BG. An assessment

radation and dechlorination of low-chlorinated biphenyls

of the impact of solar degradation of polychlori-

by a three-membered bacterial co-culture. Appl Microbiol

nated biphenyls in the aquatic environment. Chemo-

Biotechnol 1994;41:117–23.

sphere 1978;7:155–64.

41. Tiedje JM, Quensen Iii JF, Chee-Sanford J, Schimel JP,

49. Zepp RG, Baughman GL, Scholtzhauer PF. Compari-

Boyd SA. Microbial reductive dechlorination of PCBs.

son of photochemical behavior of various humic sub-

Biodegradation 1993;4(4):231–40.

stances in water: sunlight induced reactions of aquatic

42. Ahmed M, Focht DD. Degradation of polychlorinated biphenyls by two species of Achromobacter. Can J Microbiol 1973;19(1):47–52.

pollutants photosensitized by humic substances. Chemosphere 1981;10:109–17. 50. Sawhney BL. Chemistry and properties of PCBs in rela-

43. Furukawa K, Tonomura K, Kamibayashi A. Effect of chlo-

tion to environmental effects. In: Waid JS, editor. PCBs

rine substitution on the biodegrability of polychlorinated

and the Environment. Boca Raton, FL: CRC Press; 1987.

biphenyls. Appl Environ Microbiol 1978;35(2):223–7.

pp. 47–64.

44. Clark RR, Chian ESK, Griffin RA. Degradation of poly-

51. Safe S. Polychlorinated biphenyls (PCBs) and polybro-

chlorinated biphenyls by mixed microbial cultures. Appl

minated biphenyls (PBBs): biochemistry, toxicology, and

Environ Microbiol 1979;37:680–8.

mechanism of action. Crit Rev Toxicol 1984;13:319–93.

45. Novakova H, Vosahlikova M, Pazlarova J, Mackova M,

52. Mackay D, Shiu WY, Ma KC. Illustrated Handbook

Burkhard J, Demnerova K. PCB metabolism by Pseudo-

of Physical-Chemical Properties and Environmental Fate

monas sp. P2. Intern Biodeterior Biodegrad 2002;50

for Organic Chemicals. Boca Raton, FL: Lewis Publish-

(1):47–54.

ers; 1992. p. 1.

46. Rogers JD. Sequential anaerobic-anaerobic treatment

53. WHO/EURO. PCBs, PCDDs, PCDFs: Prevention and con-

of polychlorinated biphenyls in soil microcosm. Wash-

trol of accidental and environmental exposures. Environ-

ington DC: National Center for Environmental Research,

mental Health Series 23. Copenhagen: World Health Orga-

USEPA; 1999.

nization, Regional Office for Europe; 1987.

47. Ruzo LO, Zabik MJ, Schuetz RD. Photochemistry of bio-

54. Rodziewicz M, Kaczmarczyk A, Niemirycz E. Polychlo-

active compounds: photoproducts and kinetics of polychlo-

rinated biphenyls in the Sediments of the Odra River

rinated biphenyls. J Agric Food Chem 1974;22:199–202.

and its Tributaries. Pol J Environ Stud 2004;13,(2):203–8.

