Comment by azepoi

it's not perfect but it's gotten better apparently. 170 countries have signed a treaty significantly reducing the fuel sulphur content.

https://en.wikipedia.org/wiki/MARPOL_73/78#IMO_2020

https://www.imo.org/fr/MediaCentre/HotTopics/Pages/Sulphur-2...

https://www.imo.org/en/MediaCentre/PressBriefings/pages/02-I...

  The upper limit of the sulphur content of ships' fuel oil was reduced to 0.5% (from 3.5% previously) - under the so-called "IMO 2020" regulation prescribed in the MARPOL Convention. This significantly reduces the amount of sulphur oxide emanating from ships.