Monsanto owner Bayer AG and industry lobbyist CropLife America have been working closely with US officials to pressure Mexico into abandoning its intended ban on glyphosate, a pesticide linked to cancer that is the key ingredient in Monsanto's Roundup weedkillers. The moves to protect glyphosate shipments to Mexico have played out over the last 18 months, a period in which Bayer was negotiating an $11bn settlement of legal claims brought by people in the US who say they developed non-Hodgkin lymphoma due to exposure to the company's glyphosate-based products. The pressure on Mexico is similar to actions Bayer and chemical industry lobbyists took to kill a glyphosate ban planned by Thailand in 2019. Records show alarm starting to grow in the latter part of 2019 after Mexico said it was refusing imports of glyphosate from China. In denying a permit for an import shipment, Mexican officials cited the "precautionary principle", which generally refers to a policy of erring on the side of caution. Industry executives told US government officials that they feared restricting glyphosate would lead to limits on other pesticides and could set a precedent for other countries to do the same. Mexico may also reduce the levels of pesticide residues allowed in food, industry executives warned. "If Mexico extends the precautionary principle" to pesticide residue levels in food, "$20bn in US annual agricultural exports to Mexico will be jeopardized", [CropLife president Chris] Novak wrote to US officials.