Which category of NLS requires restrictions on discharge due to risks to human health and the environment?

Category Y Noxious Liquid Substances (NLS) are classified as those that may pose a risk to human health and the environment when discharged into the marine environment. This category includes substances that, while less hazardous than those in Category X, can still be harmful under certain conditions. As a result, there are specific restrictions placed on their discharge, reflecting the need to protect human health and marine ecosystems.

These substances are regulated to ensure that their potential impacts are minimized, recognizing that even lower-risk substances can have cumulative effects or be particularly harmful in certain circumstances. Therefore, when dealing with Category Y substances, the regulations are designed to prevent discharges that may lead to pollution or pose risks to health or the environment.

Category X substances are considered highly hazardous, necessitating a complete prohibition on discharge, while Category Z substances and Category A substances either have no restrictions or need stringent controls under different conditions. This understanding is key to mitigating risks associated with the handling and discharge of various kinds of noxious liquids in maritime operations.