Indian scientists on Friday said that the water in the holiday resort state of Goa was unfit for bathing and fishing due to high levels of bacteria from untreated sewage.
The National Institute of Oceanography, which is based in the former Portuguese colony, said that the level of faecal coliform bacteria in water off the coast and in rivers was higher than the international benchmark.
"For safe bathing and international standards it should be 100 CFU (colony forming units) per 100 millilitres but now it has touched 190" in some areas, said NIO scientist Dr N. Ramaiah.
Ramaiah said coastal waters tested by the scientists were generally above the limit, but the problem was most acute in the basins of Goa's two rivers, the Mandovi and Zuari.
A colony forming unit is used in microbiology to measure the number of viable bacteria. Faecal coliform bacteria can be a product of human or animal waste but also storm water run-off or plant material.
Levels of faecal coliform bacteria are one of a number of indicators of water quality and are often monitored to protect human health.
Tourism officials expressed alarm at the findings, given the state's dependence on foreign visitors. Some 400,000 overseas tourists flock to Goa each year, with its long, sandy beaches a major draw.
"If there is such a phenomenon then it is a matter of concern," said state tourism director Swapnil Naik, although he added that he had yet to see the NIO report.
The findings come after a six-year assessment of water quality off the Konkan coast in western India, where the tiny state of Goa is found.
Scientists compared levels of faecal coliform bacteria in Goa's water with overall Indian levels and those from the US Environmental Protection Agency.
"Almost all the sewage released in the rivers is untreated. Even one gram of stools contains millions and millions of coliform bacteria. So when it is present in water naturally the count goes up," said Ramaiah.
The chairman of the Goa State Pollution Control Board, Simon de Souza, said the direct discharge of untreated sewage into the state's rivers or ocean was rare.
"But there are so many residential areas along the water bodies whose sewage might have been flowing into them," he said.
Sewage is collected in septic tanks in Goa but de Souza said that most were not big enough.
He suggested that high levels of bacteria may have been caused by ground water run-off during heavy monsoon rains.