Mercury levels high in West Bengal fish samples: study

February 6th, 2009 - 8:48 pm ICT by IANS  

New Delhi, Feb 6 (IANS) The next time you bite into a delectable fish preparation, be warned there may be a hidden unwelcome ingredient - mercury.Alarming levels of toxic mercury were found in 264 samples of popular fish like Rohu, Bhola, Tangra, Aar, Bhetki and other fish varieties collected across West Bengal, results of a study released here Friday have revealed.

The trend is applicable across the country, researchers from voluntary organisations Toxics Link and DISHA said.

While 52 cases had mercury concentrates in excess of the Prevention of Food Adulteration (PFA) Act standards of 0.5 ppm (parts per million), 129 of the fish showed methyl mercury levels (a metabolized and more poisonous form of mercury) exceeding the 0.25 ppm PFA stipulations.

“The risks associated with the observed mercury concentrations found in this study suggest an alarming level. Given that a large population in West Bengal is dependent upon fish consumption, this requires public health action,” said Santanau Chacraverti, a researcher from DISHA.

One of the primary sources of mercury in nature at present is from coal firing thermal plants. Other sources are industrial effluents that are directly discharged into water bodies and municipal waste water streams.

This study is the first of its kind in the country to delve into the concentration of heavy metals in staple foods.

The study was further juxtaposed to fish consumption patterns to assess risk and it was found that the protein-rich fish were most likely to affect pregnant mothers, their foetuses and young children.

“This is because the provisional tolerable weekly intake - PTWI - is proportional to the weight of consumer and the intake quantity and degree of fish contamination,” Chacraverti said.

“So, someone having no fish or taking fish in small quantities may not be affected,” he added.

Around 181 of the samples - more than 50 percent of the fish - exceeded the PTWI threshold by 100 percent.

Further, it was found that 70 percent of the contaminated fish were the coastal/estuarine variety.

“High level of methyl mercury leads to neurotoxicity - it affects the brain’s development, stunts psychological development and can cause serious mental disorders over a gradual period of time,” said Ravi Agarwal, director Toxics Link.

“IQ levels could drop and an individual’s mental stability is jeopardised,” he added.

Other implications could be chronic ailments and motor coordination problems.

This study, researchers said, was conducted in West Bengal, primarily because fish is the staple food there and it is a coastal state.

“There is a need for real assessment to be done on a greater scale. Fish eating advisories must be given by the Indian government, and communicated to the consumers about which fish are safer to consume and in what amounts,” said Agarwal.

United Nations Environment Programme’s (UNEP) governing council, first identified mercury as a global threat over six years ago.

“Serious, concerted and global action must be taken immediately to reduce mercury levels in the environment and protect fish as an important source of protein for many communities,” Agarwal said.

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