The River Ganga passes through a large number of cities, towns, villages and agricultural fields. A sizable fraction of effluents and sewages generated from all these diverse sectors enters into the river. The incoming water is, therefore, carrying huge amounts of organic substances, residues of the used pesticides and metals along with other contaminants. Review of the pesticide residue studies indicate that hexachlorocyclohexane (HCH), dichlorodiphenyltrichloroethane (DDT) and endosulfan were the major contaminants in water and biota while HCH, DDT, aldrin and dieldrin dominate the sediment phase. In water the residues are frequently crossing the permissible limits of US EPA standards for aquatic organisms and their consumers, indicating various levels of risk. In fishes, the permissible limits for HCH, endosulfan and DDT are exceed only in some occasions, signifying minor risks on human consumption. Regarding metal contaminations, the uppermost stretch, up to Haridwar, is relatively free from pollutions. The middle stretch, receiving diverse kinds of effluents, is markedly polluted. Although a significant stretch of the estuarine zone is densely industrialized and regularly receives effluents, the tidal action is maintaining the metals in lower level than the middle stretch. However, in majority of the cases the reported levels in water were much higher than the US EPA permissible limits for aquatic organisms. With respect to the metal contaminations in sediments, the river is found moderately polluted. In some fishes, contamination of Pb, Hg and Cr crosses the limits. However, the alkaline pH, high sediment transportation and rigorous flushing during monsoons are protecting the river from accumulation of these toxic contaminants. With respect to aquatic health, it is anticipated that the metal and pesticide contaminations might have adversely affected fish health. Systematic studies are, however, lacking on this aspect.

Introduction

The Ganga River basin covers 26% of India's land mass (861,404 sq. km) and supports about 43% of the Indian population (448.3 million as per 2001 census and presently, more than 500 million). Naturally, the river passes through a large number of cities (36 class I with population >0.1 million and 14 class II with population 0.05–0.1 million), towns (48), villages (thousands) and agricultural fields. The industrial establishments in the Ganga River basin include chemical, fertilizer and pharmaceutical industries, textile and paper mills, tanneries, oil refineries, electronics plants, etc. Leather industries near Kanpur are one of the major sources of pollution which use large amounts of chromium and other toxic chemicals. Only one-third of the sewage generated in the adjoining cities and towns receives treatment before being discharged into the river. Thus, the untreated sewage and industrial wastewater are the primary sources of pollution to the river. The incoming waters carry huge amounts of organic substances, residues of pesticides and metals besides other contaminants.

A large volume of published literatures indicate wide variability in the metal and pesticide residue levels in the abiotic and biotic components of the river. The objective of this recent paper is to review the metal and pesticide pollution status of the River Ganga with the river being divided into three regions: the upper (Gangotri to Haridwar) middle (Haridwar to Farakka) and the lower (Farakka to the Bay of Bengal) stretch.

Pesticide contaminations in the Ganga River system

For agricultural and public health purposes, about 9,000 tons of pesticides are applied annually in the Ganga River basin (Ghose et al., 2009). Recent literature indicates the level to be 21,000 tons (NGRBA, 2011). The pesticide use pattern in India showed that the insecticides always dominated, followed by herbicides and fungicides. Among the insecticides, the organochlorines were the dominant group till the 1990s, after which use of organophosphates increased. During 2003, the consumption pattern was: insecticide 52%, herbicide 33% and fungicide 15%. Among the insecticides, use of organochlorines was 16%, organophosphates 50%, synthetic pyrethroids 19%, carbamates 4%, bioinsecticides 1% and others 10%.

Residues in water

Review of literatures on the residue studies in River Ganga and its tributaries indicated that hexachlorocyclohexane (HCH), dichlorodiphenyltrichloroethane (DDT), endosulfan and their metabolites are dominant in the water phase (Table 1). Unusual content from the Varanasi (middle) stretch (Nayak et al., 1995) and high content from the estuarine stretch (commonly known as River Hooghly) has been reported (Kole et al.,2005). These published values with unusually high content of different pesticides are difficult to explain.

Table 1.

Organochlorine pesticide residues in water (ng l−1) of the River Ganga and its tributaries.

Name of riverHCHDDTAldrinDieldrinEndosulfanHeptachlorChlordaneReference
Ganga 1–971 0–1240 — — 0—2890 — — Ray, 1992  
 — 0–5808 — — — — — Singh, 1992  
 0–1119 0–832 0–120 — 0–232 0–412 — Agnihotri, 1993 
 105–99517 69–143226 — — 83–66516 — — Nayak et al., 1995  
 189–2597 19–1663 0–800 — 0–862 — — Kumari and Sinha, 2001  
 0–74 0–489 — — 0–208 — — Singh et al., 2011  
Yamuna — 40–3400 — — — — — Agarwal et al., 1986  
 0–939 0–1444 0–58 0–129 — — — CPCB, 2000  
 120 660 — — — — <0.008 Anbu, 2002  
Gomti — 0–53165 0–627 — — — — Singh, 1996  
 0–4846 0–4578 0–205 — 0–1372 — — Singh et al., 2005  
Rivers of Northeast 6–214 13–218 — — 0–7 — — Pathak et al., 1992  
Tributaries of Ganga 4–26 9–72 — — — — Sarkar et al., 2003  
Hooghly 1– 400 2–560 — — — — — Thakar, 1986  
 — 6–4000 — — 0–97 — — Halder et al., 1989  
 1.5 6.2 — — — — 0.180 Anbu, 2002  
 0–18650 0–6000 — — 0–3620 — — Kole et al., 2005  
Surface water 0–3410 0–2100 — — 0–2880 — — ICAR, 2002  
– indicates data not available. 
Name of riverHCHDDTAldrinDieldrinEndosulfanHeptachlorChlordaneReference
Ganga 1–971 0–1240 — — 0—2890 — — Ray, 1992  
 — 0–5808 — — — — — Singh, 1992  
 0–1119 0–832 0–120 — 0–232 0–412 — Agnihotri, 1993 
 105–99517 69–143226 — — 83–66516 — — Nayak et al., 1995  
 189–2597 19–1663 0–800 — 0–862 — — Kumari and Sinha, 2001  
 0–74 0–489 — — 0–208 — — Singh et al., 2011  
Yamuna — 40–3400 — — — — — Agarwal et al., 1986  
 0–939 0–1444 0–58 0–129 — — — CPCB, 2000  
 120 660 — — — — <0.008 Anbu, 2002  
Gomti — 0–53165 0–627 — — — — Singh, 1996  
 0–4846 0–4578 0–205 — 0–1372 — — Singh et al., 2005  
Rivers of Northeast 6–214 13–218 — — 0–7 — — Pathak et al., 1992  
Tributaries of Ganga 4–26 9–72 — — — — Sarkar et al., 2003  
Hooghly 1– 400 2–560 — — — — — Thakar, 1986  
 — 6–4000 — — 0–97 — — Halder et al., 1989  
 1.5 6.2 — — — — 0.180 Anbu, 2002  
 0–18650 0–6000 — — 0–3620 — — Kole et al., 2005  
Surface water 0–3410 0–2100 — — 0–2880 — — ICAR, 2002  
– indicates data not available. 

Moderate content of HCH compounds was recorded in the studies of Kumari and Sinha (2001) from Bihar stretch of the river. DDT and its analogues was observed to be moderate by Ray (1992) and Halder et al. (1989). Ray (1992) also reported moderate content of endosulfan compounds. The literatures of Table 1 indicated that in the water phase the residue levels of HCH were up to 5000 ng l−1; the higher values of 1000–5000 ng l−1 were mostly from the pollutant receiving areas. In the case of DDT, the observed values exhibited similar content (0–5000 ng l−1) and trend (Table 1). For endosulfan, the level was 0–3000 ng l−1. Aldrin was not studied in all the cases. Its reported range was 0–800 ng l−1. Heptachlor was reported in one study. Chlordane was found in traces, wherever detected (Anbu, 2002).

As a whole, a decreasing trend in the organochlorine pesticide residues in Ganga water has been recorded over time and present levels of contamination are: HCH 0.1–17.6; DDT 0–12.3; endosulfan 0–85.4 and heptachlor 0–11.8 ng l−1 in the river stretch from its origin to the border of West Bengal. While the glacial melting was attributed to be the source of pesticides in the upper most stretch, the agricultural use of endosulfan contributed to a great extent in the Uttar Pradesh stretch of the river. The Bhagalpur stretch was observed to be contaminated more with aldrin and related compounds (Mutiyar and Mittal, 2012).

Although the observed residue levels are sometimes high or very high, due to prevalence of tropical climate in the country, the aquatic systems are protected from the worst state of pollution even after a huge application of the organochlorine pesticides in the past. Studies of Takeoka et al. (1991) on the fate of applied HCH to paddy fields in the coastal South India stated that about 99.6% of the applied HCH was removed to the air and only 0.4% was drained to the estuary. Moreover, about 75% of the flux to the estuary was removed to the air. Thus only 0.1% of the applied HCH was drained to the sea. The experiments of Gajbhiye and Agnihotri (1991) from Delhi area of Ganga basin also conveyed the similar message: the volatilization of surface applied lindane was 13.5–62.6% and 6.7–24.0% from soil-incorporated treatments. Thus, in aquatic systems, less amount of organochlorine pesticides are retained as residues.

Comparison of the water pesticide residue data of Table 1 with the permissible limits of United States Environmental Protection Agency (USEPA) for aquatic organisms or their consumers (Table S1) indicated that the Ganga River water is contaminated with the residues of organochlorine pesticides, the content of which often exeeded the permissible limits by thousands of times (Samanta, 2007). Thus, the aquatic organisms in the Ganges or their consumers are at risk.

A few attempts have been made to study the organophosphorus pesticide residues in water of River Ganga (Table 2). Malathion, methyl parathion and dimethoate were detected in many water samples and ethion was also found occasionally (Ray 1992). Kole et al. (2005) also confirmed similar type of observations from Hooghly estuary. Agnihotri (1993) however, reported very low concentrations of these insecticides from upper portion of middle stretch of River Ganga.

Table 2.

Organophosphorus insecticide residues in water (ng l−1) of River Ganga.

Water resourceMonocrotophosDimethoateMalathionMe-parathionEthionReference
Ganga River — 0–2694 0–6982 0–279 0–1995 Ray, 1992  
 0–185 0–137 0–1 Agnihotri, 1993  
Hooghly estuary — 0–1940 0–4830 0–3050 — Kole et al., 2005  
– indicates data not available. 
Water resourceMonocrotophosDimethoateMalathionMe-parathionEthionReference
Ganga River — 0–2694 0–6982 0–279 0–1995 Ray, 1992  
 0–185 0–137 0–1 Agnihotri, 1993  
Hooghly estuary — 0–1940 0–4830 0–3050 — Kole et al., 2005  
– indicates data not available. 

Residues in sediment

Only limited studies were done on the sediment phase of the river (Table S2) and the reported levels were also found to be low with respect to water. For HCH, the recorded range is 0–100 ng g−1. In one study however, the level was high, observed in River Gomti, the tributary of River Ganga (Singh et al., 2005). DDT and aldrin were found to be present in the range of 0–500 ng g−1. Aldrin residues were found more frequently in sediments. Endosulfan was reported in the sediments of River Gomti (0–72.6 ng g−1, Singh et al., 2005). Chlordane in the sediment of River Ganga (range <0.1–49 ng g−1) was reported by Senthilkumar et al. (1999).

Pesticide contaminations in fishes

In the fishes of River Ganga, significant accumulation of HCH and DDT was observed in some of the studies (Senthilkumar et al. 1999; Kumari et al. 2001; Table 3). Aldrin and endosulfan were relatively less. From the estuary the reported levels were relatively low (Joshi, 1986a,b; Samanta, 2006). In general, in some occasions, the organochlorine pesticide residue content in fishes of River Ganga exceeded the associated permissible limits (Table 3) for HCH (up to 7 times above the Food and Agriculture Organization of the United Nations [FAO] limit) and endosulfan (up to about 2 times above the FAO limit, Kumari et al. [2001]). Though in majority of the cases the residues of DDT in fish samples were higher than that of HCH or endosulfan, the permissible limit was not exceeded. In the estuarine zone, probably the dilution effect protected the fishes from accumulating these persistent compounds. In spite of extensive use of HCH, the residues measured in fishes in India are comparable to that of other countries (Ramesh et al., 1992). The prevailing high temperature enhanced elimination of the pesticides from fish body as the biological half lives are short under such an environment.

Table 3.

Organochlorine pesticide residues in fish (ng g−1).

Biota sourceHCHDDTAldrinDieldrinEndosulfanReference
Ganga River fish 77 160 2.7 2.9 — Kannan et al., 1993  
 28–110 60–3700 — — — Senthilkumar et al., 1999  
 55–1207 14–1666 0–225  0–175 Kumari et al., 2001  
Ganga dolphin blubber 860–1900 21000–64000 — — — Senthilkumar et al., 1999  
Yamuna River fish — 56 — — — Agarwal et al., 1986  
 — 59–7575 — — — Pillai and Agarwal,1979  
Ganga tributary fish 0–6 0–55 — — — Sarkar et al., 2003  
Gomti River fish 4–410 0 –1658 — — — Kaphalia et al., 1986  
Hooghly estuary      Joshi, 1986a,b 
 fish — 31–460 — — —  
 mollusks — 66–953 — — —  
Hooghly estuary fish 0.1–9.0 1.4–73.4 0–0.7  0–4.2 Samanta, 2006  
 0.01- 8310 0–13230 — — 0–2950 Aktar et al., 2009  
Jorhat, Assam fish 0–168 — — 0–72 Deka et al., 2005  
Safety limits for human consumption       
 US FDA — 5000 300 300 — FAO, 1983  
 FAO 100 lindane 5000 200 200 100  
 Thailand 500 lindane 5000 100 300 —  
– indicates data not available. 
Biota sourceHCHDDTAldrinDieldrinEndosulfanReference
Ganga River fish 77 160 2.7 2.9 — Kannan et al., 1993  
 28–110 60–3700 — — — Senthilkumar et al., 1999  
 55–1207 14–1666 0–225  0–175 Kumari et al., 2001  
Ganga dolphin blubber 860–1900 21000–64000 — — — Senthilkumar et al., 1999  
Yamuna River fish — 56 — — — Agarwal et al., 1986  
 — 59–7575 — — — Pillai and Agarwal,1979  
Ganga tributary fish 0–6 0–55 — — — Sarkar et al., 2003  
Gomti River fish 4–410 0 –1658 — — — Kaphalia et al., 1986  
Hooghly estuary      Joshi, 1986a,b 
 fish — 31–460 — — —  
 mollusks — 66–953 — — —  
Hooghly estuary fish 0.1–9.0 1.4–73.4 0–0.7  0–4.2 Samanta, 2006  
 0.01- 8310 0–13230 — — 0–2950 Aktar et al., 2009  
Jorhat, Assam fish 0–168 — — 0–72 Deka et al., 2005  
Safety limits for human consumption       
 US FDA — 5000 300 300 — FAO, 1983  
 FAO 100 lindane 5000 200 200 100  
 Thailand 500 lindane 5000 100 300 —  
– indicates data not available. 

Aquatic biota, other than fish, was studied only in a few cases. In the dolphin (Platanista gangetica) blubber of the river, huge accumulation of DDT and considerably high HCH were reported (Senthilkumar et al.,1999). Because of the lipophilic character of the organochlorine substances, very high biomagnifications were reported in literature across the globe. One such study was conducted in the Hooghly estuary to determine the bioconcentration factor of DDT. The observed levels of DDT in different components of the food chain are presented in Figure 1. The bioconcentration factor of 7500 for fish and 15833 for bivalves indicated a risk associated with the terrestrial consumers including human beings. Reports of Brown (1978) clearly indicated the harmful effects of applied organochlorine pesticides in the aquatic ecosystems where the biomagnification factors and pesticide concentrations were comparable with the present findings.

Figure 1.

Concentration of DDT (ng g−1) in different components in River Hooghly. (Color figure available online.)

Figure 1.

Concentration of DDT (ng g−1) in different components in River Hooghly. (Color figure available online.)

Like the abiotic component, only limited studies reported for other groups of insecticides. In fishes, high content of dimethoate (0–5020 μg kg−1) and malathion (0–5400 μg kg−1) has been recorded in one such work (Aktar et al., 2009). No study has so far been made to determine the residues of the herbicides and fungicides in abiotic and biotic components of River Ganga and its tributaries.

Metal contaminations in the Ganga River system

Among the various pollutants, metals are of added concern due to their environmental persistence, biogeochemical recycling and ecological risks. The combined effect of the basin characteristics (relief, geology, climate, vegetation, size of the drainage area etc.) and the anthropogenic activities (urban development, promotion of industries, mining, agriculture, deforestation etc.) govern the type, composition and quantity of metals accumulated and transported through the river. Contrary to studies with pesticides, research work with metal contaminations in River Ganga is more common and hence, only the main channel was considered.

Contaminations in water

The uppermost stretch of the River Ganga, up to Haridwar, is reported to be relatively free from metal contaminations. In some studies however, a significant amount of Hg (0.081 μg l−1) has been reported from Rishikesh (Sinha et al., 2007). The middle stretch, receiving different kinds of effluents, is reported to be heavily polluted with different metals (Cd 0-28, Cr 2-119, Cu 0-170, Zn 1-311 μgl−1 water dissolved metals, Table 4). Although a significant stretch of the estuarine zone is densely industrialized and regularly receives effluents, the mixing and dilution with tidal water is maintaining the metal levels in water lower than that of the middle stretch (Vass et al. 2008). Elevated levels of water dissolved Hg, Ni, Pb and Zn were however, registered at the same time from the estuary (Kar et al., 2008; Sarkar et al.,2007).

Table 4.

Metal contaminations in water (μg l−1) of River Ganga.

RiverCdCrCuHgMnNiPbZnReference
Ganga (upstream) 2–11 — 8–17 — 27 -116 12–50 — 75–157 Saikia et al., 1988  
 — — — 72 Joshi, 1991  
Ganga (midstream) 57 28 — 93 — Mohammed et al., 1987  
 0–1 5–32 3–49 — 35–211 1–10 1–6 61–311 Israili, 1991  
 0–1 — 0–1 — — — 1–5 2–6 Singh et al., 1993a  
  2–3  — — — — 18–41 Singh et al., 1993b  
 0–2 — 0–7 — — — 0–4 1–6 Singh et al., 1993 
 5–7 – 20–170 — — — 80–680 30–230 Vass et al., 1998  
 28 3–119 17–106 — — — — — Gupta and Raghubanshi, 2002  
 5–8 — 62–140 — — — 102–166 7–23 Untoo et al., 2002  
 — — — 0–2 — — — — Sinha et al., 2007  
 0–12 (8) 0–18 (12) 0–30 (17) — — — 18–86 (43) 26–122 (72) Gupta et al., 2009  
Hooghly estuary 0–10 0–10 6–38 — — — 0–6 37–248 Joshi, 1994  
 8–70 — 10–70 — — — 40–300 20–80 Vass et al., 1998  
 20 — 79–90 — — — 69–129 64–92 Ghosh et al., 2000  
 20–60 10–60 0–50 — 0–40 — 30–160 10–50 Nath et al., 2003  
 2–14 — 5–19 — 8–88 — 17–41 22–37 Samanta et al., 2005  
 — — — 160–950 — — 17–76 — Sarkar et al., 2007  
 0–3 0–44 0–32 — 0–2720 12–375 0–250 0–370 Kar et al., 2008  
Ganga (midstream) Effluent water 63–115 13–106 177–228 — 380–9242 344–1035 2–5 202–613 Prasad et al., 1989  
 14 200 179 — — — 26 285 Joshi, 1991  
Hooghly estuary Effluent water — — 0–500 — — — 0–8500 Ghosh et al., 1983 
US EPA limit for aquatic organisms          
Fresh water 0.25 11 / 74 9.0 — — 52 2.5 120  
Saline water 8.8 50 3.1 — — 8.2 8.1 81  
– indicates data not available. 
RiverCdCrCuHgMnNiPbZnReference
Ganga (upstream) 2–11 — 8–17 — 27 -116 12–50 — 75–157 Saikia et al., 1988  
 — — — 72 Joshi, 1991  
Ganga (midstream) 57 28 — 93 — Mohammed et al., 1987  
 0–1 5–32 3–49 — 35–211 1–10 1–6 61–311 Israili, 1991  
 0–1 — 0–1 — — — 1–5 2–6 Singh et al., 1993a  
  2–3  — — — — 18–41 Singh et al., 1993b  
 0–2 — 0–7 — — — 0–4 1–6 Singh et al., 1993 
 5–7 – 20–170 — — — 80–680 30–230 Vass et al., 1998  
 28 3–119 17–106 — — — — — Gupta and Raghubanshi, 2002  
 5–8 — 62–140 — — — 102–166 7–23 Untoo et al., 2002  
 — — — 0–2 — — — — Sinha et al., 2007  
 0–12 (8) 0–18 (12) 0–30 (17) — — — 18–86 (43) 26–122 (72) Gupta et al., 2009  
Hooghly estuary 0–10 0–10 6–38 — — — 0–6 37–248 Joshi, 1994  
 8–70 — 10–70 — — — 40–300 20–80 Vass et al., 1998  
 20 — 79–90 — — — 69–129 64–92 Ghosh et al., 2000  
 20–60 10–60 0–50 — 0–40 — 30–160 10–50 Nath et al., 2003  
 2–14 — 5–19 — 8–88 — 17–41 22–37 Samanta et al., 2005  
 — — — 160–950 — — 17–76 — Sarkar et al., 2007  
 0–3 0–44 0–32 — 0–2720 12–375 0–250 0–370 Kar et al., 2008  
Ganga (midstream) Effluent water 63–115 13–106 177–228 — 380–9242 344–1035 2–5 202–613 Prasad et al., 1989  
 14 200 179 — — — 26 285 Joshi, 1991  
Hooghly estuary Effluent water — — 0–500 — — — 0–8500 Ghosh et al., 1983 
US EPA limit for aquatic organisms          
Fresh water 0.25 11 / 74 9.0 — — 52 2.5 120  
Saline water 8.8 50 3.1 — — 8.2 8.1 81  
– indicates data not available. 

In the majority of the cases the reported levels (Table 4) were much higher than the USEPA permissible limits for aquatic organisms. Thus, the aquatic community is at risk due to water dissolved metals of the River Ganga. The effluents entering into the river were found contaminated with metals and sometimes the contaminations were unusually high, as was observed by Prasad et al. (1989), Joshi (1991) and Ghosh et al. (1983).

Contaminations in sediment

Metal content in sediment of River Ganga has been studied in detail by a number of workers (Table S3). In the upper stretch, as per expectations, the metal contents were found low. Since the area is free from human activities, the metal contents were attributed to the geochemical sources. In the middle stretch (Rishikesh to Ramghat near Bulandshahr), highest content of the metals was recorded in the Ghaziabad stretch receiving industrial discharges. Although the Kanpur stretch of the river is reported to be heavily polluted (NRCD, 2009), this was not reflected in the metal content in sediment. As a whole the river is found moderately polluted with respect to the permissible limits of heavy metals in sediments.

Khwaja et al. (2001) conducted a study to determine the impact of the tannery effluents on the River Ganga as it passes through Kanpur. There are about 150 tanneries in and around Kanpur. The general parameters BOD, COD, chlorides, total solids, phenols and sulphides in water were recorded to have increased. The most striking impact noticed was about a 10 fold increase in Cr content in the sediment surface. While in the upstream stretch total Cr in winter was 52.5 μg g−1, in the downstream the content increased to 320.1 μg g−1. Generally, the Fe-Mn oxide fraction was found to have the greatest increase.

In general, for study of metal contaminations in rivers, the water dissolved and sediment bound metals are routinely monitored. However, the water dissolved metals are frequently transferred to the particulate state, adsorbed on the suspended sediments and carried with the moving phase. Such transportation of metals is very important especially with the estuarine stretch having different levels of tidal energy. An exhaustive study conducted by Mukherjee (2012) emphasised the role of suspended sediments in metal transportation in River Hooghly, the stretch having very high sediment load (annually 560 million tons) and strong tides, up to 5.5 m. In the suspended sediments higher enrichment factor for Cu, Cd, Ni, Cr and Zn was recorded due to anthropogenic activities related to poor land uses for urbanization and industrialization. The wastewater from Kolkata has also been found not to be the major source of metal pollution of the river (Mukherjee 2012). As a whole, the metal enrichment factors observed in River Hooghly was found relatively low compared to that reported for other rivers of the world.

Metal contaminations in fishes

In some of the studies dry weight of fishes were considered while in other cases it was wet weight. So, during comparison necessary calculations were taken into account. The Rishikesh to Kolkata stretch of the River Ganga was studied by Joshi (1991). The levels of Cr, Cu, Pb and Zn were found high in the fish samples from the middle stretch, while Hg was high in the estuarine samples (Table 5). From the middle stretch of the river (Varanasi region) significant accumulation of Hg was observed (up to 91.7 μg g−1) in the tissue of Macrognathus pancalus (Sinha et al., 2007). In other fishes however, the recorded Hg content was relatively less (up to 3.2 μg g−1). Kaviraj (1989) reported relatively high content of Zn (135.6 μg g−1) in Penaeus indicus from Hooghly estuary. Among the studied fishes, Mastacembelus pancalus accumulated more amount of Zn (108.2 μg g−1). As per the United States Food & Drug Administration (US FDA) limit for human consumption, the contaminations of Pb, Hg and Cr exceeded the limits on some occasions in fish tissue (US FDA, 2001). As a whole, the numbers of studies are limited.

Table 5.

Metal contaminations in fish and prawns (μg g−1).

FishCdCrCuHgMnNiPbZnReference
Rita rita (Dry weight) — 1.75 11.8 0.485 — — 14.5 80.9 Joshi, 1991  
Miscellaneous fish (Dry weight) — — 31.2 0.53 — — — 189.6 Joshi, 1991  
Rita rita from midstream (Dry weight) 0.35–0.49 3.9–11.2 — — — — 0.0–6.0 — Khan et al., 2003  
Ganga (mid stream) — — — 0–91.68
2.64 
— — — — Sinha et al., 2007  
Ganga (mid stream) Channa punctatus 0.026–0.048 (0.038) 0.056–0.072 (0.062) 0.42–0.96 (0.64) — — — 1.86–2.89 (2.42) 6.42–12.84 (9.50) Gupta et al., 2009  
Ganga (mid stream) Aorichthis aor 0.034–0.056 (0.042) 0.048–0.092 (0.0.072) 0.80–1.20 (0.92) — — — 2.46–3.89 (3.12) 8.62–20.86 (14.13) Gupta et al., 2009  
Hooghly estuary Sperata seenghala — — 5.29 0.03 2.36 — — 29.4 Mohanty et al., 2012  
Hooghly estuary          
Fish 0.14–0.50 3.4–17.4 3.3–47.7 — — — — 4.4–108.2 Kaviraj, 1989  
Prawn 1.92 1.4 19.8     135.6  
Hooghly estuary Fish — — 0–340 — 0–20 0–20 — 0–340 Bhattacharya et al., 1994  
US FDA limit*          
Crustacea 12 —  — 70 1.5 — US FDA, 2001  
Molluscan bivalve 13 — (methyl mercury) 1 — 80 1.7 —  
*US FDA limit for human consumption on wet weight basis.– indicates data not available. 
FishCdCrCuHgMnNiPbZnReference
Rita rita (Dry weight) — 1.75 11.8 0.485 — — 14.5 80.9 Joshi, 1991  
Miscellaneous fish (Dry weight) — — 31.2 0.53 — — — 189.6 Joshi, 1991  
Rita rita from midstream (Dry weight) 0.35–0.49 3.9–11.2 — — — — 0.0–6.0 — Khan et al., 2003  
Ganga (mid stream) — — — 0–91.68
2.64 
— — — — Sinha et al., 2007  
Ganga (mid stream) Channa punctatus 0.026–0.048 (0.038) 0.056–0.072 (0.062) 0.42–0.96 (0.64) — — — 1.86–2.89 (2.42) 6.42–12.84 (9.50) Gupta et al., 2009  
Ganga (mid stream) Aorichthis aor 0.034–0.056 (0.042) 0.048–0.092 (0.0.072) 0.80–1.20 (0.92) — — — 2.46–3.89 (3.12) 8.62–20.86 (14.13) Gupta et al., 2009  
Hooghly estuary Sperata seenghala — — 5.29 0.03 2.36 — — 29.4 Mohanty et al., 2012  
Hooghly estuary          
Fish 0.14–0.50 3.4–17.4 3.3–47.7 — — — — 4.4–108.2 Kaviraj, 1989  
Prawn 1.92 1.4 19.8     135.6  
Hooghly estuary Fish — — 0–340 — 0–20 0–20 — 0–340 Bhattacharya et al., 1994  
US FDA limit*          
Crustacea 12 —  — 70 1.5 — US FDA, 2001  
Molluscan bivalve 13 — (methyl mercury) 1 — 80 1.7 —  
*US FDA limit for human consumption on wet weight basis.– indicates data not available. 

General observations

Ganga River water is alkaline with a recorded range of 7.0–9.2 (Vass et al., 2008) which facilitates metal ions to precipitate out on the sediment phase. Thus, the metals transported into the river system are retained mostly in the bottom sediments. The prevailing alkaline pH also facilitates faster decomposition of pesticide molecules. The Ganga Brahmaputra River system has very high sediment transportation load, amounting to 1620 × 106 tons annually, of which 1000 × 106 tons are carried as suspended load and 620 × 106 tons as the bedload. It has been observed that nearly 80% of bedload sediments are moved as “graded suspension” during the monsoon season. Thus, the river bed is flushed during every monsoon, preventing higher accumulation of toxic contaminants like metals and pesticides.

The impact of the metal and pesticide contaminants present in water and sediments of River Ganga and its tributaries on biotic community were studied only to a limited extent. A significant degree of genotoxicity of Ganga River water was reported by Rehana et al. (1995) with the use of Ames Salmonella test due to contamination of organochlorine pesticides in the upper part of middle stretch of the river. Fish sperm motility was found hindered due to the presence of insecticides which impacted the endocrine system of fishes from the polluted stretches of Rivers Ganga and Gomti (Singh et al., 2008). Studying the anomalous nuclei and micro nuclei in fish blood cells, the genotoxic effect of Hooghly-Matlah River water was found prominent and differed significantly from one site to the other; the metal contaminations in the estuarine mouth were reported to be the probable cause for such abnormalities (Mallick and Khuda-Buksh, 2003).

Conclusions

Metal and pesticide residue content in water and sediments of River Ganga clearly indicates that the river is contaminated and the aquatic organisms are at various levels of risks depending upon the levels of contaminations. It is anticipated that the metal and pesticide contaminations might have adversely affected the health of aquatic organisms. Systematic studies are however, lacking on this aspect. While aquatic health is greatly impaired, the human health aspects due to consumption of fishes from River Ganga is not too alarming since only in a limited number of cases have the associated permissible limits been exceeded. It is, however, high time to implement all the possible regulations to protect the holy River Ganga, the lifeline of the vast Indian plains and that of Indian civilization.

Acknowledgements

The author is thankful to Professor A. P. Sharma, Director and Dr. M. K. Das, Head, FREM Division, Central Inland Fisheries Research Institute, Barrackpore, for guidance and encouragement.

[Supplementary materials are available for this article. Go to the publisher's online edition of Aquatic Ecosystem Health and Management to view the free supplementary files.]

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Supplementary data