Assessment of heavy metals, pesticides and parasites in Villorita cyprinoides along central Kerala

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3 Assessment of heavy metals, pesticides and parasites in Villorita cyprinoides along central Kerala OBJECTIVES: To assess the hazard associated with Villorita cyprinoides in relation to heavy metals, pesticides and parasites along central Kerala. INTRODUCTION: As a part of AP Cess Funded National Network Project on NATIONAL RISK ASSESSMENT PROGRAMME FOR FISH AND FISH PRODUCTS FOR DOMESTIC AND INTERNATIONAL MARKETS, CMFRI, Kochi was entrusted to study the hazards associated with heavy metals, pesticides and parasites in the black clam, (Villorita cyprinoides), a commercially important bivalve along central Kerala during MODE OF SAMPLING: Approximately 750g of fresh meat of V. cyprinoides were collected at monthly intervals to study the chemical hazards (heavy metals and pesticides). Monthly, about live bivalves from each station were collected for the study of parasites. METHODOLOGY: The analysis of heavy metals and pesticides were done following standard procedures. Heavy metals: The heavy metals in the meat of bivalves were extracted following the AOAC method (1995). Samples were digested using concentrated HNO 3 and concentrated H 2 SO 4. Heavy metal content in the digested samples was estimated by Atomic Absorption Spectrophotometer (Perkin Elmer AA700) using the appropriate hollow cathode lamp and flame AA method. Arsenic and Hg were analyzed in graphite furnace AA method. Pesticides: The method developed by FAD (1995) was followed for the extraction of pesticides. The organochlorine pesticide extraction from the meat includes, sample preparation, extraction of fat, acetonitrile partitioning, clean up in flurosil column and quantification in the Gas Chromatography. After extraction process, the samples were quantified for pesticides in the GC. Parasites: In order to study the presence of parasites of human health significance in the selected bivalves, the animals were examined in live condition. The collected V. cyprinoides (15mm 40mm) samples from the respective stations were carried to the CMFRI laboratory 1

4 and maintained alive. After measuring the basic morphometrics, the shells of the bivalves were opened using a knife. The adductor muscles were cut opened and the meat was transferred into a petri dish without losing the mantle fluid. Consequently, mantle, mantle fluid, ctenidia, gonad, gut, muscle, hepatopancreas etc., were examined separately for the presence of parasites/associates/commensals under different magnifications of stereo zoom microscope and under higher magnifications of a research microscope (Leica) and photographed. Hemolymph and tissue smears were prepared and observed. Abnormalities in various tissues, abscesses, lesions, blisters etc. whenever present were recorded and further subjected to histological studies. RESULTS Heavy metals : Detection and violation of different heavy metals in V. cyprinoides studied during the period from July 2003 to December 2005 is presented in Table 1. Mean concentration of different heavy metals in V. cyprinoides is shown in Table 2. The trends of seasonal concentrations of heavy metal in V. cyprinoides are represented as Fig.1 to 6. The concentrations of As, Cr, Hg and Zn were more in post monsoon than in pre monsoon and monsoon in 2003 and No consistent trend was observed in Cd concentration. The Pb concentration was more in monsoon than in pre monsoon and post monsoon in 2003 and Pesticides: Detection and violation of various organochlorine pesticides in V. cyprinoides studied during 2004 to 2005 are furnished in Table 3. Mean concentration of different pesticides in V. cyprinoides during the period is presented in Table 4. No consistent seasonal variation in the concentration of various organochlorine pesticides was noticed in any of the bivalve samples analysed (Fig. 7 13). Parasites: During the study, a total of 500 live V. cyprinoides from the central parts of Kerala were examined for the presence of parasites of sanitary/phytosanitary significance. All the animals examined during this study were free of parasites of sanitary significance. Whereas, organisms of phytosanitary significance were recorded with varying prevalence. Ectocommensal ciliates and turbellarians were recorded from almost all the 2

5 bivalves examined whereas trichodina, nematodes and copepods were observed only in some of the samples (Fig 14). CONCLUSION: During the study period from July 2003 to December 2005, the heavy metals were found to accumulate in the bivalve samples and the concentration showed a wide range of levels. There was no pertinent seasonal variation in the concentration of heavy metals in the bivalves studied. With regard to mean concentration of Cd and Pb, the concentration gradually reduced from 2003 and reached well below the permissible limits by Mean concentration of Cr was below the detectable levels in 2003, and was within the permissible levels in It was found that As within the permissible levels only in most of the samples during the study period. Mercury, though detected in few samples, didn t cross the permissible limits in any of the sample so far analysed. While considering the risk with parasites, all the bivalves examined during the study period were fully free of any hazard due to parasites of sanitary significance. Though some organisms of phytosanitary significance were observed in V. cyprinoides during the study, their prevalence was low and as such does not act as a serious threat. 3

6 Table 1 : Detection and violation of heavy metals in V. cyprinoides (July 2003 Dec 2005) Heavy metals Permissible Concentration (ppm) WHO standards Number of samples July2003 June 2004 (N= 8) July2004 June 2005 (N=24) July2005 Dec 2005 (N=12) Detection Violation Detection Violation Detection Violation As 4 8 (100%) nil 22 (91%) 12 (50%) 12 (100%) nil Cd 2 8 (150%) 4 (50%) 12 (50%) 2 (8%) 1 (8.3%) nil Cr 2 4 (50%) 2 (25%) 18 (75%) 12 (50%) 12 (100%) 6 (50%) Hg (100%) 2 (25%) 18 (75%) nil 12 (100%) nil Pb 2 4 (50%) 2 (25%) 2 (8%) 2 (8%) 6 (50%) nil Zn 50 8 (100%) nil 24 (100%) nil 12 (100%) nil Table 2: Mean heavy metal concentration (ppm) in V. cyprinoides (July 2003 Dec 2005) Heavy metals Concentration in ppm Mean SD Mean SD Mean SD As Cd Cr Hg Pb Zn ND ND

7 Table 3 : Detection and violation of pesticides in V. cyprinoides (Jan 2004 Dec 2005) Table 4: Mean of pesticide concentration (ppb) in V. cyprinoides (Jan 2004 Dec 2005) 5

8 Figures 1 6 Concentration of heavy metals in the tissues of V. cyprinoides 6

9 Figures 7 13 Concentration of pesticides in the tissues of V. cyprinoides 7

10 Figures 14 Organisms of phytosanitary significance reported from V. cyprinoides 8