France bans popular weedkiller S-metolachlor over water pollution

France’s food safety authority Anses has moved to ban S-metolachlor, a common herbicide used by cereal farmers, because of significant groundwater pollution. The product joins an increasingly growing list of chemicals no longer allowed in French agriculture.

A sprinkler waters corn crops in fields on the outskirts of te soutern French city of Toulouse. AFP - JEAN-PIERRE MULLER

Although it’s less well-known than glyphosate, S-metolachlor is widely used in France to prevent weeds corn, sunflower and soybean crops. Nearly 2,000 tons of this root herbicide was sold in 2020, making it the country’s third most popular herbicide. 

Once spread in the soil, the active substance breaks down into metabolites that migrate into the soil, surface water and groundwater. Although it does not present an immediate health risk, Anses said the molecule was a major source of water pollution. 

"In tests of drinking water, the metabolites of S-metolachlor have frequently been detected at concentrations exceeding the quality standards,” Anses said.

Restrictions

The ban follows earlier measures by health authorities to clamp down on dose allowances for S-metolachlor’s use in corn, sunflower, soybean and sorghum fields.

Charlotte Grastilleur, deputy director of the regulated products division at Anses, said the results of the agency’s tests were indisputable.

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“Despite recent restrictions on the conditions of its use, the limit of 0.1 microgram per litre set by European legislation in groundwater is exceeded for three metabolites of S-metolachlor,” Grastilleur said.

Companies who manufacture S-metolachlor have been informed of the withdrawal procedure, and cereal growers have been given 6 to 12 months to sell their grains before switching to an alternative weed killer.

The ban on S-metolachlor comes weeks after French sugar beet farmers were prohibited from using "bee-killing" neonicotinoid pesticides.