A new report says Swiss trading companies are blending and dumping dirty fuel in West Africa with more than 100 percent the sulfur levels allowed in Europe, causing health and environmental hazards.

The report "Dirty Diesel" from Swiss watchdog group Public Eye says the companies take advantage of weak African standards to use cheap and dirty additives to create what's called "African Quality" fuels.

The practice is not illegal. The report quotes Swiss trading giants Oryx, Trafigura and Vitol as noting that the blends meet standards in the importing countries, with the largest amounts going to Nigeria, Senegal and Ghana.

But Public Eye accuses the companies of lowering a fuel's quality to just above a country's legal limits to maximize profits by adding toxic products known to cause respiratory diseases.