Section 4(1)(b) in Calcutta Slum Clearance and Rehabilitation of Slum-Dwellers Act, 1958
(b)the-unhealthy or unhygienic condition thereof or of the huts or other structures therein, is dangerous or injurious to public health or to the health of the inhabitants of the area, the State Government may, by notification, and in such other manner as may be prescribed, proclaim its intention to declare such area to be a slum-area.