On average, a cruise ship generates 15 gallons of toxic chemicals each day. These materials come from on-board dry cleaning and photo-processing facilities, painting and other activities. Seven thousand gallons of oily bilge water are released into the oceans every time the ship empties its bilge tanks.

Cruise ships are often criticized for their significant environmental footprint, primarily due to air emissions, sewage, and solid waste. Large vessels often burn Heavy Fuel Oil (HFO), which releases high levels of sulfur oxides (SOx), nitrogen oxides (NOx), and particulate matter that can cause respiratory issues in port cities. A single large cruise ship can produce over 150,000 gallons of sewage (blackwater) and 1 million gallons of greywater (from sinks/showers) every week. While modern ships use Advanced Wastewater Purification Systems (AWPS), older ships may still discharge treated waste into the open ocean. Furthermore, ships generate massive amounts of solid waste—roughly 50 tons per week—much of which is incinerated on board, releasing additional toxins. In 2026, the industry is transitioning toward "greener" technologies, such as Liquefied Natural Gas (LNG) and shore-power connections, to reduce localized "toxicity" in ports. However, environmental groups remain concerned about "methane slip" from LNG engines and the overall impact of cruise-related carbon emissions on the global climate.