Fish contamination by radionuclides: Fish in Pulicat lake contain polonium and radioactive lead

By Syed Akbar
Hyderabad:  Nellore chepala pulusu or fish curry is a delicacy which every 
gourmet would vouch for. A research study, however, reveals that the fish caught in the 
famous Pulicat lake and marine waters in Nellore district is contaminated by the 
radionuclides of polonium (Po 210) and lead (Pb 210).

What is worrying is that the concentrations of these radionuclides in the edible tissues 
of fish and shrimp are higher than those of fishes caught in Palk Strait in the country 
and the Marshall Island in the USA.

Also the committed effective dose (i.e. the quantity of radiation consumed by people 
through the seafood) from Nellore marine fish is higher than the one observed in Bombay 
Harbour bay and Kalpakkam, where nuclear plants are located. Though the researchers did 
not study the fish and shrimp caught in inland aquaculture ponds, they may also contain 
the radionuclides if the seed was procured from Pulicat lake or nearby marine sources.

According to official statistics of the fisheries department, 56,693 metric tonnes of 
marine fish is being exported to different countries from Nellore every year after 
processing at Chennai. In case of marine shrimp, 8,664 metric tonnes is exported from 
Nellore apart from 12,120 metric tones of brackish water shrimp per annum.

A considerable portion of the seafood from Nellore is sold in markets in large cities 
including Chennai, Hyderabad, Kolkata and even Dhaka in Bangladesh. Pulicat lake alone 
produces 5030 tonnes of marine fish and 692 tonnes of marine shrimp every year.

The research was carried out by teams from the department of biotechnology, Bharathidasan 
University, Tiruchirapalli, and the postgraduate and research department of zoology, New 
College, Chennai. “The activity concentration of Po 210 and Pb 210 were determined in the 
edible muscle tissues of 20 fish species. The concentrations vary between 38.3 Bq.kg 
(Becquerel per kilogram) to 109.3 Bq.kg in case of radioactive polonium and 0.72 Bq.kg to 
2.7 Bq.kg for radioactive lead,” the researchers, R Krishnamoorthy and MS Musthafa, 
pointed out in their study published in the latest issue of the prestigious science 
journal, Radiation Protection and Environment.

They found that the radioactive contamination was due to the naturally occurring uranium 
series accumulated in the body, especially radioactive polonium (Po 210). In the marine 
ecosystem Polonium 210 is largely produced from the decay of radioactive lead deposited 
by human pollution in the form of industrial waste and untreated sewage.

The researchers noted that the Pulicat lake and the marine environs in Nellore is 
polluted by industries including North Chennai Thermal Power Plant, Ennore port, Manali 
Petrochemical Industries, and untreated urban wastes from Chennai metropolitan.