Five West African countries have announced measures to end the practice of European oil companies and traders exporting “dirty diesel”, The Guardian reported.

Swiss commodity traders were accused in a report published in September by Swiss NGO Public Eye of exporting fuels to West Africa with Sulphur levels that are sometimes hundreds of times higher than European levels.

Nigeria, Benin, Togo, Ghana, and Cote d’Ivoire agreed on the import ban, informed BBC News. The UN says the move will help more than 250 million people breathe safer and cleaner air. The five countries also agreed to upgrade their national refineries to bring locally produced diesel up to the same quality by 2020.

Permitted levels of Sulphur in imported diesel will fall from as high as 3,000ppm (parts per million) in some of the countries to 50ppm. In Europe, the maximum has been 10ppm since 2009. The Sulphur particles emitted by a diesel engine are considered to be a major contributor to air pollution and are ranked by the World Health Organization (WHO) as one of the top global health risks.