Section 6(1)(a) in The Merchant Shipping (Control of Pollution by Noxious Liquid Substances in Bulk) Rules, 2010
(a)Category X: Category X is the category of noxious liquid substances which, if discharged into the sea from tank cleaning or de-ballasting operations, are deemed to present a major hazard to either marine resources or human health and justify its prohibition from discharge into the marine environment: