What is Annex 2 of MARPOL 73/78(Regulation for the Control of Pollution by Noxious Liquid Substances in Bulk )and discharge regulations?

2. Category Y:

Noxious liquid substances which if discharged into the sea from tank cleaning or deballasting operations are deemed to present a hazard to either marine resources or human health. Therefore Justify the limitation on the quality and quantity of the discharge into marine environment.

3. Category Z:

Noxious liquid substances which if discharged into the sea from tank cleaning or deballasting operations are deemed to present a minor hazard to either marine resources or human health therefore justify less stringent restrictions on the quantity & quality of the discharge into marine environment.