Environmentalist Anil Sinha has sent a letter to Prime Minister Narendra Modi to make the Sariswa free of pollution. A copy of it has been marked to Union water resources minister Uma Bharati.

Sinha, also a social activist, has been demanding measures to make the river pollution-free for about four years under the banner of “Sariswa Nadi Bachao Andolan”. Dumping of industrial waste into the river has endangered the existence of 10 lakh people in India and Nepal, living on either side of the river on a stretch of about 25km.

The Sariswa originates from the Ramban forest range in Nepal. It culminates in the Sikrahna river of Bihar.

Father Kristo Das, a disciple of Mother Teresa, had established the state’s biggest leprosy centre then on the banks of the Sariswa in Raxaul in 1981. The water of the river was used for treatment.

Three decades on, the water of the Sariswa has become toxic following discharge of industrial wastes in Nepal. Following a prolonged public protest under the banner of “Sariswa Nadi Bachao Andolan”, a survey was conducted in Nepal in September 2013.

About 46 industrial units in two districts of the neighbouring country were found guilty of dumping industrial wastes in the Sariswa,” said Sinha. Orders were also issued to initiate stern administrative action against 13 of them. But even affluent water treatment plants had not been installed there because of the unstable government in Nepal and lack of will power, said Sinha.