Congress President Rahul Gandhi on Sunday expressed concern over the deteriorating health of Gopal Das, who is on a fast for the conservation of river Ganga and currently in a hospital.Das was admitted to the All India Institute of Medical Sciences, Rishikesh, on Saturday, two days after environmentalist G.D. Agarwal died following a fast for over 100 days.Agarwal, popularly known as Swami Sanand, had been on a hunger strike since June 22 for a pollution-free Ganga and an uninterrupted flow of water in the river."The deteriorating health of Gopal Das is a concern for the whole country. He has been on hunger strike since June 24 seeking prevention of mining in Ganga. Gopal Das is now the voice of Agarwal and this voice must be strengthened," Gandhi said on twitter.The Congress has attacked Prime Minister Narendra Modi for "neglecting" the repeated pleas of Agarwal, who had written several letters to the Prime Minister voicing his concern over Ganga pollution.