Ships are typically powered by heavy fuel oil or bunker oil, both of which produce harmful pollutants such as sulphur dioxide which can cause respiratory and heart problems.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/europe-set-compliance-chaos-new-ship-fuel-sulphur-rules
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/planet-ark-australia
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/europe
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-pollution
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/shipping
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/health-effects
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/respiratory-diseases
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/heart-diseases
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/liquefied-natural-gas-lng