Monsanto also produced seeds which grow into plants genetically engineered to be tolerant to glyphosate, which are known as Roundup Ready crops.

In June 2020, Bayer agreed to pay $9.6 billion to settle tens of thousands of claims, mostly alleging that glyphosate-based Roundup had caused cancer.

[20][21] Independent scientific reviews and regulatory agencies have repeatedly concluded that glyphosate-based herbicides do not lead to a significant risk for human or environmental health when the product label is properly followed.

[22] The acute oral toxicity for mammals is low,[18] but death has been reported after deliberate overdose of concentrated Roundup.

[25] Consumption of over 85 ml of concentrated product is likely to cause serious symptoms in adults, including burns due to corrosive effects as well as kidney and liver damage.

[21] In a 2017 risk assessment, the European Chemicals Agency (ECHA) wrote: "There is very limited information on skin irritation in humans.

[26] Inhalation is a minor route of exposure, but spray mist may cause oral or nasal discomfort, an unpleasant taste in the mouth, or tingling and irritation in the throat.

[18] Aquatic organism exposure risk to terrestrial formulations with POEA is limited to drift or temporary water pockets.

[16] While laboratory studies can show effects of glyphosate formulations on aquatic organisms, similar observations rarely occur in the field when instructions on the herbicide label are followed.

[31] The consensus among national pesticide regulatory agencies and scientific organizations is that labeled uses of glyphosate have demonstrated no evidence of human carcinogenicity.

The final assessment of the Australian Pesticides and Veterinary Medicines Authority in 2017 was that "glyphosate does not pose a carcinogenic risk to humans".

[37] In the ten months following Bayer's June 2018 acquisition of Monsanto, its stock lost 46% of its value because of investor apprehension concerning the 11,200 lawsuits filed against its subsidiary.

In a statement they said the outcome was "consistent with the evidence in this case that Roundup does not cause cancer and is not responsible for the plaintiff's illness".

[47][48] Johnson had routinely used two different glyphosate formulations in his work as a groundskeeper, RoundUp and another Monsanto product called Ranger Pro.

[55][56] U.S. District Judge Vince Chhabria stated that a punitive award was appropriate because the evidence "easily supported a conclusion that Monsanto was more concerned with tamping down safety inquiries and manipulating public opinion than it was with ensuring its product is safe."

Chhabria stated that there was evidence on both sides as to whether glyphosate causes cancer, and that the behavior of Monsanto showed "a lack of concern about the risk that its product might be carcinogenic.

"[54] On May 13, 2019, a jury in California ordered Bayer to pay a couple $2 billion in damages (later cut to $87 million on appeal[57]) after finding that the company had failed to adequately inform consumers of the possible carcinogenicity of Roundup.

[11] In 1996, Monsanto was accused of false and misleading advertising of glyphosate products, prompting a lawsuit by the New York State attorney general.

[64] Monsanto had made claims that its spray-on glyphosate based herbicides, including Roundup, were safer than table salt and "practically non-toxic" to mammals, birds, and fish, "environmentally friendly", and "biodegradable".

[65] Citing avoidance of costly litigation, Monsanto settled the case, admitting no wrongdoing, and agreeing to remove the offending advertising claims in New York State.

[65] Environmental and consumer rights campaigners brought a case in France in 2001 accusing Monsanto of presenting Roundup as "biodegradable" and claiming that it "left the soil clean" after use; glyphosate, Roundup's main ingredient, was classed by the European Union as "dangerous for the environment" and "toxic for aquatic organisms".

[66][67] On 27 March 2020 Bayer settled claims in a proposed class action alleging that it falsely advertised that the active ingredient in Roundup Weed & Grass Killer only affects plants with a $39.5 million deal that included changing the labels on its products.

[68] In June 2023, Bayer reached a $6.9 million settlement agreement with the New York attorney general, settling false advertising allegations concerning the safety of Roundup.

[72] In January 2019, Roundup Pro 360 was banned in France following a Lyon court ruling that regulator ANSES had not given due weight to safety concerns when they approved the product in March 2017.