|Year : 2011 | Volume
| Issue : 2 | Page : 110-113
Assessment of committed effective dose to human beings due to consumption of fishes collected from Pulicat Lagoon, south east of India
M Saiyad Musthafa1, R Krishnamoorthy2
1 Post Graduate and Research Department of Zoology, The New College, Chennai, India
2 Department of Biotechnology, Bharathidasan University, Tiruchirappalli, Tamilnadu, India
|Date of Web Publication||12-Jul-2012|
M Saiyad Musthafa
Post Graduate and Research Department of Zoology, The New College, Chennai
Source of Support: None, Conflict of Interest: None
The activity concentration of 210 Po and 210 Pb were determined in the edible muscle tissues of 20 fish species collected from Pulicat Lagoon, south east of India. The concentrations were found to vary between 38.3 Bq.kg - - 109.3 Bq.kg - and 0.72 Bq.kg - - 2.7 Bq.kg - for  Po and  Pb respectively. These variations in the  Po and  Pb content in different species were probably due to differences in metabolism and feeding patterns. Appropriate conversion factors were used to derive the committed effective dose for human consumers, which were found to be 73.3 1 - 209.1 μSv.yr -1 and 2.2 - 19.3 μSv.yr -1 for 210 Po and 210 Pb respectively.
Keywords: Committed effective dose, fish, natural radioactivity, pulicat lagoon
|How to cite this article:|
Musthafa M S, Krishnamoorthy R. Assessment of committed effective dose to human beings due to consumption of fishes collected from Pulicat Lagoon, south east of India. Radiat Prot Environ 2011;34:110-3
|How to cite this URL:|
Musthafa M S, Krishnamoorthy R. Assessment of committed effective dose to human beings due to consumption of fishes collected from Pulicat Lagoon, south east of India. Radiat Prot Environ [serial online] 2011 [cited 2020 Aug 6];34:110-3. Available from: http://www.rpe.org.in/text.asp?2011/34/2/110/98396
| 1. Introduction|| |
A large contribution to the radiation dose received by marine fauna comes from members of the naturally occurring uranium series accumulated in the body, especially 210 Po .  In the marine ecosystem Polonium-210 (t 1/2 = 138.4 days) is largely produced from the decay of 210 Pb deposited from the atmosphere. 210 Po is found to be the major contributor (90%) to the natural radiation dose coming from the alpha-emitting radionuclides received by most marine organisms.  The 210 Po is strongly accumulated in marine organisms and their variations with selected biological factors and environmental fluctuations are well documented. ,,,,,,,,
Researchers in many countries and several international organizations have determined the concentrations of these radionuclides in seafood and the annual intake. Hence, the radiation doses due to its consumption have been evaluated. ,, Yu, et al., 1997;  Pietrazak-Flis Chrzanowski and Dembinska, 1997).  The most well known high background radiation area (HBRA) in India is the south west coastal region, i.e., Kerala, at the same time the south east coast also has some sparse distribution of high levels of radiation. In the east coast one nuclear power plant is functioning at Kalpakkam and one is under construction at Kudankulam. There is no systemic data for natural radionuclides in the biota of Pulicat Lagoon. This present baseline study determines the concentrations in fishes and committed effective dose due to 210 Po and 210 Pb.
| 2. Materials and Methods|| |
2.1. Study area - Pulicat Lagoon
The Pulicat Lagoon situated between 13 o 25' - 13 o 55' N latitude and 80 o 03' - 80 o 19' E longitude with an altitude of 0 - 10 m. This is the second largest brackish water lagoon in India running parallel to the Bay of Bengal, bordering the east coast of Andhra Pradesh with a portion of it extending into the northern part of Tamil Nadu [Figure 1]. The lagoon is about 360 sq km in size, and its depth (water column) varies from 1 to 6 m. The point sources of pollution are mainly from North Chennai Thermal Power Plant, Ennore port activities, Manali Petrochemical Industries, other nearby industries and untreated urban wastes from Chennai metropolitan. ,
2.2. Analysis of 210 Po in Fishes
The flesh part of the fishes were dried, homogenized and transferred to a 400 mL beaker and repeatedly digested with a concentrated HNO 3 :H 2 O 2 (1:1) oxidizing mixture until a white ash was obtained. The residue was evaporated with concentrated HCl repeatedly to convert to chloride medium, then taken up in 0.5 N HCl and 210 Po was plated on a silver planchette by electrochemical deposition method and the activity was alpha counted following the method given below.
2.3. Electrochemical deposition of 210 Po
The sample solution in 0.5 N HCl was placed on a magnetic stirrer with thermostat control at a temperature of 90 o C. Ascorbic acid (100 mg) was added to reduce ferric ions to ferrous, thus eliminating its interference in electrochemical deposition of polonium. A silver planchette (0.8 mm thickness and 2.5 cm diameter) of predetermined background and whose both sides were brightly polished with emery paper was suspended in the sample solution by means of a nylon thread at the end of a glass rod, connected to a stirrer. The silver planchette was kept spinning for a period of 5-6 h with the aid of the stirrer. Spontaneous deposition of 210 Po on both sides of the silver planchette took place under these conditions. At the end of the plating period, the planchette was taken out, rinsed with alcohol, dried under infrared lamp for few minutes and counted for activity on both sides in an alpha counter. Deposition efficiency of 210 Po on biological samples spiked with uranium ore solution containing equilibrium activity of 210 Po using the above method yielded a recovery range varying from 95 to 100% with an average efficiency of 98±2%. The counting instrument used was a radiation counting system (ECIL-RCS 4027-A) with an alpha counter of ZnS (Ag) detector (ECIL-SP 647-A) having a background of 0.1-0.2 cpm and a counting efficiency of 25-28% for 239 Pu (244.4 dpm) standard source.
2.4. Analysis of 210 Pb in Fishes
The flesh part of the fishes were dried, homogenized and repeatedly digested with a concentrated HNO 3 + H 2 O 2 (1:1) mixture to achieve complete decomposition until a white ash was obtained. The residue was leached with 2 N HNO 3 , filtered and made up to 50 mL. This solution was then used for 210 Pb determination.
2.5. Determination of 210 Pb
To the above-mentioned solution (50 mL), Pb carrier (100 mg) and Ba carrier (10 mg) were added and boiled. Sulfates were then precipitated with 9 N H 2 SO 4 . The 210 Pb carried on the Ba (Pb) SO 4 precipitate was dissolved in ammoniacal EDTA. Barium sulfate was then precipitated with acetic acid leaving the carrier Pb and 210 Pb in solution. The solution was stored for 50 days to allow for the growth of 210 Bi. Bismuth carrier (10 mg) and Ca carrier (200 mg) were then added and Bi (OH) 3 was precipitated with ammonia. Then, Bi (OH) 3 was dissolved in 0.5 N HNO 3 . The 210 Bi was then precipitated with H 3 PO 4 as BiPO 4 , which was then washed, dried and counted for beta activity in a special type of low background beta-counting system. The counting system consisted of a gas flow type GM counter with argon as the counting gas and isopropyl alcohol vapor as the quenching agent, coincidence and anticoincidence technique was used to reduce the background. A 15- cm thick lead shield surrounding the detector also reduced the background considerably. The background of the counting system was 1.5-2.0 cpm, with a counting efficiency of 40% for 40 K beta energy. The sample purity was checked by following up the 210 Bi decay over a 120-h period, and the final activity was calculated by applying the necessary corrections for decay, chemical recovery (80±4%), date of sampling, etc. Spiked experimental recoveries on water and biological samples using the above method yielded an overall efficiency of 90%.
2.6. Committed Effective Dose calculations
Committed effective doses (CEDs) were calculated using conversion factors (Sv Bq−1 ) for adults adopted in the coordinated project MARDOS,  namely, 4.3×10−7 for 210 Po and 6.9×10−7 for 210 Pb. Therefore, the dose calculations proceeded using the following formulas:
Where D Po-210 and D Pb-210 are the CED values for 210 Po and 210 Pb, respectively (Sv yr−1 ), C Po-210 and C Pb-210 are the radionuclide concentrations in the edible part of fish (Bq kg− 1 w.w. = wet weight), and Ir is the ingestion rate (kg yr−1 ). The ingestion rate used for fish is the international mean  equal to 4.45 kg yr−1 .
| 3. Results and Discussion|| |
The activity concentration of 210 Po and 210 Pb measured in the flesh part of fishes were collected from Pulicat Lagoon, south east Coast of India are given in [Table 1]. All the results are discussed on the basis of dry weight.
|Table 1: Concentrations and committed effective dose of 210Po and 210Pb in fishes from Pulicat Lagoon, South East Coast of India|
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The 210 Po concentrations varied between 38.3 and 109.3 Bq kg− 1 . The highest value (109.3 Bq kg− 1 ) was observed in Johnius dussmieri, followed by Oreochromis mossambicus (105.1 Bq kg− 1 ) and Leiognathus splendens (102.6 Bq kg− 1 ). The 210 Po concentrations are low in other species. In addition, the difference in these levels of radioactivity in different species of fish could be due to differences in metabolism and feeding patterns. The higher concentration of 210 Po observed in these fishes could possibly due to their benthic mode of life and detritivore feeding, which tend to accumulate more 210 Po. The 210 Pb concentration in the muscle of fish ranged from 0.72 - 2.7 Bq.kg -1 . The 210 Po and 210 Pb concentrations in the edible tissues of fish are higher in the present study than reported for fishes in Palk Strait Coastal environment, India  and Marshall Island, America.  The values of 210 Po and 210 Pb concentrations were lower in the present study than those reported for fishes in marine environments of Japan and Syria. ,
The annual dose received by the general public via ingestion of 210 Po through dietary components is important from the fact considerable variations in the intake levels of 210 Po (Holtzman, 1980).  Radiation dose deposition in human body due to consumption of seafood can be estimated by two methods .  The first is based on the 210 Po and 210 Pb concentrations in the marine water of the fishing areas. The second method is based on the 210 Po and 210 Pb concentrations in the edible tissues of fish. The committed effective dose was found to be 73.3 - 209.1 μSv.yr -1 and 2.2 - 19.3 μSv.yr -1 for 210 Po and 210 Pb respectively. The CED to the public from 210 Po due to consumption of seafood from Bombay Harbor bay (2.1- 40.0 μSv.yr -1 ) and Kalpakkam environment (36.3 μSv.yr -1 ) were lower than the present study reported by. , The present study indicated that the dose transfer to inhabitants of the Pulicat lagoon through 210 Po intake was higher when compared to those in Bombay coast and Kalpakkam coast.
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