That re-post of a re-post of an Guardian article about a study seems to have mutated to a point of becoming untrue.

The study claims, among other things, that the freighters create a lot of sulphur emisions, and that the EU has currently cleaned up car requirements so that they don't emit much sulphur in exhaust - thus, 15 largest freighters emit as much SOx as all the cars. It assumes that world's cars fit EU emission standards, which is false, and posting in this context seems to assume that the sulphur oxides cause global problems, which is also false - the bad effects of SOx pollution are rather localized, and if we can replace 1 unit of SOx in the middle of a city with 2 units of SOx in the middle of an ocean, then I'd treat that as good thing.

A more appropriate citation (from the same original article, actually) is the following - it still shows some space for improvement, but is significantly diffferent than the untrue alarmist claim in the parent post.

"Shipping is responsible for 18-30% of all the world's nitrogen oxide (NOx) pollution and 9% of the global sulphur oxide (SOx) pollution."