MARPOL Annex II

MARPOL Annex II controls pollution by noxious liquid substances carried in bulk by chemical tankers. It categorizes each substance as X, Y, Z, or Other Substances by environmental hazard, with X the most harmful and prohibited from discharge. Discharge of residues is allowed only under controlled conditions, generally at least 12 nautical miles from land, in more than 25 metres of water, and below set concentrations, with prewash requirements for category X and some Y cargoes. Operations are recorded in the Cargo Record Book and governed alongside the IBC Code.