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Maseca Corn Flours Test Positive for Toxic Residues of Monsanto Weedkiller

Leading international brand also tests positive for genetically modified organisms, despite marketing claims of ‘100 percent natural.’

October 9, 2018

Mexico: Ercilia Sahores,, +52 (55) 6257 7901
US: Katherine Paul,, (207) 653-3090

MEXICO CITY - Organic Consumers Association Mexico (ACO), a project of US-based Organic Consumers Association (OCA), today announced that samples of Maseca brand white and yellow corn flours tested positive for residues of glyphosate and its main metabolite, AMPA. Glyphosate is the active ingredient in Monsanto’s Roundup weedkiller.

“It’s clear from our testing that Maseca’s claims of selling a ‘natural’ and ‘nutritious’ product are false and misleading,” said OCA’s international director, Ronnie Cummins. “Consumers in Mexico and the US who care about pesticide contamination and GMOs should seek organic non-GMO alternatives to Maseca flours until the company agrees to source only non-GMO grains for its products.”

ACO test results on samples of Maseca white and yellow corn flour, sourced from different regions of Mexico, showed glyphosate concentrations of between 5.14 ppb to 17.59 ppb. Some flour samples tested as high as 94.15 percent for the presence of genetically modified organisms (GMO).

Activists have fought for and won a temporary ban on the open-field production of GM corn in Mexico. Mexico’s incoming president, Andres Manuel Lopez Obrador has said that GMO corn will be permanently banned from Mexico when he takes office on December 1.

In March 2015, the World Health Organization classified glyphosate as a probable human carcinogen.

In a landmark and potentially precedent-setting case, a California jury recently awarded $289 million to a terminally ill former school groundskeeper who said the exposure to Roundup caused his non-Hodgkin lymphoma.

Fairfield, Iowa-based Health Research Institute conducted the tests, under FAO testing protocols.

Maseca, owned by Mexico-based Gruma, S.A.B. de C.V., is the leading international brand of corn flours used widely in the production of tortillas.

The Organic Consumers Association (OCA) is a US-based 501(c)(3) nonprofit consumer advocacy organization focused on food, agriculture and environmental issues.