S. Kokila*, V. Bhuvaneswari and G.P. Jeyanthi
Dept. of Biochemistry, Avinashilingam Deemed University, Coimbatore - 641 043, T.N., India
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In the present study, physicochemical characteristics of zinc electroplating industry effluent were analysed. Ames Salmonella assay using the strains Salmonella typhimurium TA 98 and TA 100 was carried out to screen for the mutagenicity of zinc electroplating industry effluent. The health status of zinc electroplating industry workers was assessed by estimating various hematological parameters. The genotoxic effect of the effluent was assessed by studying the frequency of chromosomal aberration and Sister Chromatid Exchange (SCE) in peripheral lymphocytes of the zinc electroplating industry workers.Analysis of various physicochemical parameters revealed the hazardous effect of zinc electroplating industry effluent. Ames Salmonella assay confirmed the mutagenicity of zinc electroplating industry effluent. The analysis of various hematological parameters in zinc electroplating industry workers revealed decreased hemoglobin, Red Blood Cell (RBC) count and Packed Cell Volume (PCV) and increased White Blood Cell (WBC) count in the industry workers when compared to those of respective control subjects. Genotoxic studies in electroplating industry workers revealed higher frequencies of chromosomal aberration and SCE when compared to the control group participants
Zinc electroplating industry, Physicochemical parameters, Mutagenicity, Biochemical parameters, Genotoxicity.
Industrialization and urbanization has caused inevitable effects on all the three components of the physical environment viz., air, water and soil which are being subjected to increased pollution in the recent past (Kumar et al , 2003) Electroplating and metal finishing are widely practised and provide support to many major industries (Bhatt, 1998). Electroplating industries are using highly toxic and hazardous chemicals and metal ions which find their way into the effluent (Singh and Singh, 1997).
Occupational exposure to many chemicals results in various forms of poisoning and other diseases (Sundararaju, 2003). Industrial workers are exposed to a variety of chemicals which are mutagens or carcinogens which produce chromosomal aberrations in human somatic cells (Yadav et al., 2002). Sister chromatid exchange assay has been shown to be one of the sensitive short term genotoxicity assays owing to its availability to detect genotoxins at very low doses (Panda, 1995).
The present study was designed to assess the toxicological effect of zinc electroplating industry effluent by analysing selected physicochemical parameters. The mutagenic effect of zinc electroplating industry effluent was also analysed by Ames Salmonella assay. The health status of zinc electroplating industry workers was assessed by estimating the selected biochemical parameters. Chromosomal aberration and SCE were also carried out to assess the genotoxic effect of the effluent in the selected subjects.
A zinc electroplating industry located near Gandhipuram, Coimbatore city was selected for the present study. Ten litres of the untreated effluent sample and water used for electroplating purposes were collected thrice at an interval of fifteen days and stored in clean plastic cans at 4°C till analysis. Colour and turbidity were monitored visually. pH and electrical conductivity were measured using digital pH meter and conductivity bridge respectively. Analysis of Total Suspended Solids (TSS), Total Dissolved Solids (TDS), Chemical Oxygen Demand (COD), Total Hardness (TH), Sulphate,Calcium, Magnesium and Zinc were made by adopting the standard methods (APHA, 1998) and Biochemical Oxygen Demand (BOD) by adopting the standard method (APHA, 1989). Chloride was analysed by silver nitrate titrimetric method (Vogel, 1964). Sodium and potassium were analysed by Flame photometric method (Natarajan et al., 1988).
The mutant bacterial strains of Salmonella typhimurium TA 98 and TA 100 were obtained from B.N.Ames, Biochemistry Department, University of California, U.S.A. The mutagenic effect of the effluent in different dilutions namely effluent and distilled water in the ratio 1: 20 (E1), 1 : 40 (E2) and 1: 60 (E3) were tested by Ames Salmonella assay using the strains TA 98 and TA 100. The assay was done by the method of Maron and Ames (1983).
Twenty male workers in the age group of 15-60 years involved in various stages of electroplating processes were selected for the study. Twenty healthy male volunteers in the same age group, residing in Karamadai, 30 Km away from Coimbatore city and free from industrial pollution were selected as controls and parallel studies were conducted on them as in experimental group. 5ml of venous blood was collected aseptically from each participant and the samples were analysed for their hemoglobin content, Red Blood Cell (RBC) count, White Blood Cell (WBC) count and Packed Cell Volume (PCV) by the method followed by Wintrobe et al. (1965).
The venous blood samples of the experiment and control subjects were collected with aseptic precautions in tubes containing heparin. Blood sample containing heparin was used for lymphocyte culture to study the chromosomal aberration and sister chromatid exchange (Kulkarni et al., 1982).
The results obtained for the selected physicochemical parameters analysed in zinc electroplating industry effluents are presented in Table 1.
The study indicated that the zinc electroplating industry effluent was dark brown and turbid. The pH of the effluent was found to be in acidic range and below the permissible limits prescribed by the Bureau of Indian Standards. The selected physicochemical parameters studied in the effluent were higher when compared to those of water used for plating and above the tolerance limits. The dark colour of the effluent and turbidity might be due to the presence of metals and chemicals which are extensively used for electroplating processes. The discharge of the effluent into the water bodies might be detrimental to the aquatic biota, since low pH values affect the physiology of the organism. The higher levels of TDS in the effluent might be due to the presence of bicarbonates, sulphates and chlorides of calcium, magnesium and sodium. The increased levels of TSS and TDS caused the ecological imbalance in the aquatic system by affecting the light penetration and turbidity of the water (Thirumathal and Sivakumar, 2003). The present study revealed high level of BOD in the effluents indicating the presence of high organic load in the sample. High level of COD indicates that the effluent is unsuitable for the existence of aquatic organisms (Paneerselvam et al., 2003). The increased level of total hardness in the effluent is mainly due to its calcium and magnesium contents (Dhankar and Sangwan, 2004). The higher levels of chloride, sulphate, calcium, magnesium, sodium, potassium and zinc in the effluent might be due to increased use of these salts in electroplating operations.
Table 2 depicts the results obtained for the presence of mutagenicity in different dilutions of the effluent samples using standard strains TA 98 and TA100 of Salmonella typhimurium by Ames assay. A significant increase in the number of colonies was noticed when the effluent samples E1, E2 and E3 were added to both standard revertants (SR) and standard mutagens (SM) The result confirmed the mutagenicity of the effluent. Cerna et al., (1996) studied the genotoxicity of different industrial effluents and river waters and reported the mutagenic activity of the different industrial effluents. According to White et al. (1996), effluents collected from metal refining industries were significantly more genotoxic than those collected from pulp and paper mills.
Figures 1, 2 and 3 show mean levels of hemoglobin, RBC count and PCV in the selected workers of zinc electroplating industry. Hemoglobin content, RBC count and PCV in the electroplating industry workers of both the age groups decreased significantly at 5% level when compared to that of the respective control groups. There was also a significant difference in the above mentioned parameters between the different age groups of the industry workers.
Figure 4 shows the mean levels of WBC in selected workers of zinc electroplating industry. A significant increase in WBC count was obtained in the test samples when compared to that of the respective control groups. There was also a significant difference in the WBC count between the different age groups of the industry workers.
The observed variations in hematological parameters in the industry workers might be due to the presence of toxic compounds in the effluent to which they are exposed or due to their socio-economic status.
Table 3 and Plate 1 depict the results of the in vivo chromosomal aberration studies of six normal subjects and those of six industry workers. A significant increase in the frequency of cells with chromosomal aberrations was observed in zinc electroplating industry workers when compared to that of normal controls.
The mean levels of sister chromatid exchange of the selected zinc electroplating industry workers and normal controls are shown in Table 4. The present study revealed a significant increase in SCE frequencies in the industry workers when compared with that of the controls.
Exposure to physical or chemical agents, viruses and life style habits including smoking and alcohol consumption affect the genetic material of the individuals that can be detected in the form of various types of chromosomal aberrations and provide us with one of the most sensitive biological indicators of exposure. The present study on chromosomal aberrations and SCE confirmed the mutagenic and genotoxic effect of zinc electroplating industry effluent.
The results of the present investigation indicated that exposure to toxic chemicals leads to an increased risk of genetic damage among the workers of zinc electroplating industries.