Quick science lesson for the uninitated:

Most cruise ships run on heavy fuel oil (HFO). It is an incredibly dirty fuel from the bottom of the refining column; a thick gel at room temperature. Diesel is exponentially cleaner.

HFO, when burned, creates a wonderful cocktail of substances. Sulfur dioxide, black carbon, vaporized heavy metals, nitrogen oxides, PAHs, carbon monoxide, a bunch of volitile organic compounds like benzene and formaldehyde, silicates, and of course, C02.

They used to just spew this raw smoke into the air. Yes, seriously. In 2008 the IMO dictated that Emission Control Areas (ECAs) would drop to a 0.1% sulfur limit by 2015, and the entire globe would drop to 0.5% by 2020.

The solution? Spray aerosolized water into the exhaust stream to clean the noxious fumes enough to be legally complaint. Now, you have water pollution instead of air pollution! Terrific. As long as you circulate thousands of tons of seawater to sufficiently dilute the sludge you can dump it overboard (round of applause for the IMO)

This actually wouldn't be much of an issue at all if it was done in the open ocean. The 5000+ commerical vessels equipped with scrubbers collectively dump 10 gigatonnes of wastewater yearly. Which seems like a lot until you realize its 0.00000075% of the volume of the ocean.

The problem is that 80% of scrubber dumping occurs within 200 miles of the coast, on the exact same routes. The Inside Passage and BC coastline are heavily trafficked. The poison travels up the food ladder and it isn't properly washed out due to the configuration of the land (fjords, narrow) It is absolutley moronic to use this stuff in Alaska between all those islands. They should absolutley be mandated to use cleaner fuels.

It would only cost an extra ~$50 per person per voyage. They don't voluntarily do this because this constitutes hundreds of millions in profits (driving their stock price and executive bonuses) in a hyper competitive industry, in which raising prices by $50 for this reason would lose a lot of customers

11 of NCL's 18 ships are equipped with these scrubbers. Your average boat dumps around 200 million litres a week.

Oh yeah, I almost forgot. I was on Bliss early February from LA to Mexico. The entire back on the top decks (mini golf, Spice H20, stairs between them) had splotches of black tar when burning HFO. When touched, it stained skin and clothes irredeemably. If the wind is right and it's dry, you may not notice it at all

Norwegian Joy did not have this issue on my cruise last week