Section 6(1) in The Merchant Shipping (Control of Pollution by Noxious Liquid Substances in Bulk) Rules, 2010
(1)For the purpose of these rules, noxious liquid substances shall be divided into four categories as follows, namely;-(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:(b)Category Y: Category Y 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 hazard to either marine resources or human health or cause harm to amenities or other legitimate uses of the sea and justify a limitation on the quality and quantity of its discharge into the marine environment;(c)Category Z: Category Z 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 minor hazard to either marine resources or human health and justify less stringent restrictions on the quality and quantity of its discharge into the marine environment;(d)Other Substances: Other substances include substances indicated as os (Other Substances) in the pollution category column of chapter 18 of the International Bulk Chemical Code which have been evaluated and found to fall outside Category X, Y or Z because, at present, they are considered to present no harm to marine resources, human health, amenities or other legitimate uses of the sea when discharged into the sea from tank cleaning of de-ballasting operations and the discharge of bilge or ballast water or other residues or mixtures containing only substances referred to as 'Other Substances' shall not be subject to any requirements of these rules.
