POLYCHLORINATED BIPHENYLS (PCB's) - Environmental Implications

ENVIRONMENTAL ASSESSMENT OF PCB's

 The Polychlorinated biphenyls (PCB's) are the class of pollutants, which impart considerable impact on the environment and human life due to their significant acute toxicity, high lipid activity and high bio-accumulation capacity. It has been estimated that substantial quantity of Aroclors had already been loaded in the environment globally, since the time PCB's were introduced and commercially used. The major amount of PCB's is released to the atmosphere during burning of paper, plastic or paint, and rest released to fresh and coastal water by leaks, disposal of industrial wastes, leaching and atmospheric fallout. Because of these reasons the PCB's have been recognized as the first industrial (non-pesticidal) product identified as ubiquitous environmental pollutants.

 PCB's were detected first in the environment in the late 1960s and were reported globally as contaminants in almost every component of the ecosystem including air, water, soil, fish, wildlife, human blood etc. (Holdrinet et.al., 1977). The lipophilic properties of PCB's enhance bio-accumulation and biomagnification and thus various sources within the environment can lead to human exposure. The PCB's environmental concentrations in various environmental matrices are presented below:

 Air
PCB concentrations in air varies from location to location, with the lower levels usually observed over the oceans and over non-industrialized regions. The average concentrations of Aroclors (calculated as Aroclor 1242 plus Aroclor 1254) in indoor air in work places in United States ranged from 44 to 240 ng/m3. Outdoor levels of PCB's upto 18 ng/m3 were observed. In the indoor air of homes in United States, the air samples from 14 areas (of which 9 were kitchens) were analyzed. The average concentrations of PCB's in the kitchens ranged from 150 to 500 ng/m3 and in other rooms from 39 to 170 ng/m3.

Water
Surface water may be contaminated with PCB's from direct discharge from point sources or alongwith atmospheric fall out. Because of adsorption on suspended particles, PCB's concentrations in heavily contaminated water may be several times greater than their solubility. It has been established that polluted rivers, lakes and estuaries have higher PCB values than non-polluted water.

Table 4 PCB’s level in various Environmental Matrices

Environmental Matrices

Country

PCB’s concentration

range

Reference

Air

Canada

0.002-0.07 ng/m3

Bidleman et.al. , 1978

Germany

0.003-3.3 ng/m3

DFG, 1988

Japan

4-650 µg/m3

Tatsukawa & Waterable, 1972

Sweden

0.8-3.9 ng/m3

(Industrial air borne Particulate Matter)

Ekstedt & Oden, 1974

USA

1-50 ng/m3

Panel on Hazardous Substances, 1972

Water

Germany

5-103 ng/l

Lorenz & Neumeier, 1983

Sweden

0.1-0.3 ng/l

Ahnoff & Josefsson, 1974

Netherlands

100-500 ng/l

Wegman & Greve, 1980

USA                      

100-450 ng/l

Panel on Hazardous Substances, 1972

India

0.19-1.93 ng/l

CPCB, 1999

Soil

Germany

0.02-0.08 ng/kg

Markard, 1988

Japan

< 1 ng/kg

Fukada et.al. , 1973

United Kingdom

0.2-12.2 µg/kg

Jones, 1989

2.3-55 µg/kg

USA

0.6-1.7 ng/kg

Nimmo et.al. , 1971

India

0.616-8.93 µg/kg

CPCB, 1999

ng/m3  =     Nanogram per cubic meter;          ng/l  =       Nanogram per litre;     µg/kg   =    Microgram per kilogram

Source : Polychlorinated Biphenyls and Terphenyls; WHO Environmental Health Criteria, 140.

PCB's in Water and Sediments of River Yamuna and Drains in Delhi
PCB's level in water and sediments have been assessed at five locations of Delhi stretch of River Yamuna and five major drains joining river Yamuna during May, 1999. The water and sediment samples collected from river and drains were pre-treated at CPCB Laboratory and forwarded to National Institute of Oceanography (NIO), Goa for Gas Chromatographic analysis of PCB's. The analysis results of total PCB's in river water, drain water and river and drain sediments are presented in Table 5 and the findings of the study are as below.
  • Minimum and maximum levels of PCB's in water samples were found at old Yamuna Bridge and at Okhla i.e. 0.190 ng/l and 1.926 ng/l respectively, whereas in sediment samples minimum and maximum levels of PCB's were observed at Palwal (0.616 ng/g) and at Palla (8.927 ng/g) respectively.
    Table  5 Concentration of Total PCB’s in water and sediment samples of Yamuna River and drains in Delhi

    S. No.

    Sampling locations

    Total PCB’s in sediments (ng/g)

    Total PCB’s in water (ng/l)

    A. YAMUNA RIVER

    1.

    River Yamuna at Palla

    8.927

    0.505

    2.

    River Yamuna at Old Yamuna Bridge

    1.140

    0.190

    3.

    River Yamuna at Nizamuddin Bridge            

    1.908

    1.289

    4.

    River Yamuna at Okhla

    0.641

    1.926

    5.

    River Yamuna at Palwal

    0.616

    0.501

    B. DRAINS

    1.

    Najafgarh Drain

    8.300

    1.476

    2.

    Civil Mill Drain

    281.397

    4.738

    3.

    Power House Drain

    0.282

    6.545

    4.

    Sen Nursing Home Drain

    1.361

    0.288

    5.

    Shahdara Drain

    5.010

    1.540

  • Among the major drains, the total PCB's in the drain water was recorded in the range 0.288 to 6.545 ng/l, whereas in sediments PCB's were in the range 0.282 to 281.397 ng/g. The highest concentration of PCB's in water and in sediment were detected in Power House Drain and Civil Mill Drain, respectively.
  • The results indicate that after mixing of Civil Mill Drain and Power House Drain with river Yamuna, the PCB's levels in river water increased from 0.190 ng/l (at Old Yamuna Bridge) to 1.926 ng/l (Okhla) indicating that PCB's are contributed by the drains alongwith the wastewater. The level of PCB's again decreased to 0.501 ng/l down stream to Okhla, may be due to dilution or PCB's removal through bio-accumulation.
  • The US Environment Protection Agency (USEPA) Guidelines has recommended the criteria limit of 14.0 ng/l in its National Recommended Water Quality Criteria for Non-priority pollutants in fresh water (Ref: Federal Register, Vol. 63 No. 237, 1988). The analysis results indicate that PCB's levels in water at all the locations of river Yamuna as well as in drains are well within the limit.
Soil
Soil may become contaminated with PCB's from direct discharge from point sources. The presence and behavior of PCB's in the soil depend on congener specific characteristics and on a number of soil parameters. Sorption and condensation processes in the soil plays major role in the removal of PCB's. PCB's accumulate in the sediments of rivers and lakes and this accumulation indirectly reflect the contamination of water. An important, though localized, source of PCB's contamination of soil can be the use of sewage sludge as a fertilizer in agriculture. PCB's levels varying from 0.1 to 765 ng/kg (dry weight) have been reported in sewage sludge from different countries, the usual range being 0.1 to 9.0 mg/kg (WHO/EURO, 1987).

PCB's Levels in Human Food
The presence of specified isomers of PCB congeners in Canada in fatty foods of the Canadian diet had been studied by Mes et.al. (1989) in which total of 93 food composites from the cities of Ottawa and Halifax were analyzed for 34 PCB's isomers. The PCB's isomers 118, 138, 153 and 180 were found in all dairy products, except skimmed milk while, cheese and butter contained the highest levels of PCB residues. The residue level of PCB isomer 118 (2,3',4,4',5-pentachlorobiphenyl) in butter was the highest while 0.7 µg/kg of all PCB isomers were found in dairy products. Almost all meat, fish and poultry contained PCB isomers 183 and 187. Occasionally, isomers 49, 87, 185 and 189 were also present.

Fresh water fish contained most PCB isomers (28 out of 34 selected PCB isomers), at levels considerably higher than those in any other meat, fish or poultry samples. The level of isomer 110 in fresh water fish was 3.05 µg/kg.

The PCB levels obtained in the food in an extensive study at United States during 1972 by the US Food and Drug Administration are presented in Table 6.


                                        Table  6  PCB’s Levels in Food in United States of America

S.No.

Food items

% Sample  with positive presence of PCB’s

(0.1 µg/kg)                 

Levels in the food samples

(mg/kg)

Min
Max

1.

Cheese

6

0.25

1.0

2.

Milk

7

2.3

27.8

3.

Eggs

29

0.55

3.7

4.

Fish

54

1.87

35.3