SAO PAULO, Oct 5 (Reuters) - Brazilian labor prosecutors have requested a court order to ban the use of atrazine, which is present in 5% of pesticides sold in the country, the prosecutors said on Thursday.

National health regulator Anvisa, which would be forced to cancel the registration of pesticides containing atrazine if a judge rules in favor of the labor prosecutors, did not immediately have a comment on the lawsuit filed on Wednesday in a Brasilia court.

Atrazine, which is used on crops from sugarcane to corn and soy, was banned in the European Union in 2003 due to the risk of contaminating groundwater.

Nine years later it was also forbidden in Switzerland, the headquarters of Syngenta, which developed the herbicide and continues to produce and export the chemical, prosecutors said.

On its website, Syngenta calls atrazine "safe for people" and "good for the environment and the economy," citing studies that attest to its safety on U.S. farms, where its use is permitted.

In a statement, Syngenta said it does not directly sell atrazine in Brazil and that it imports the active ingredient, "which serves as the basis for other formulations that are produced and applied in the country."

The company also said atrazine is registered in more than 50 countries and called it a crucial tool for helping farmers manage weeds and increase crop yields.

Brazil, whose tropical climate has made it an agribusiness powerhouse, is the world's largest consumer of pesticides, including many banned elsewhere. Researchers estimate that Brazil accounts for about 20% of total global pesticide use.

Prosecutors cited 2021 data from Brazilian environmental agency Ibama, the most recent available, showing atrazine was the country's fifth most used pesticide ingredient. The best seller was glyphosate, a weed-killer that genetically modified soybeans are designed to tolerate.

Brazil, the world's biggest soybean and sugar exporter and a major corn grower, imported about 77,700 tons of products containing atrazine in 2022, mainly from China, which accounted for about 80% of supplies, according to Brazilian government trade data.

The United States and Israel also export the chemical to Brazil, the data showed. (Reporting by Ana Mano; Editing by Brad Haynes and Aurora Ellis)