The Oakland jury on Monday, May 13 delivered the agribusiness giant’s third such loss in California since August.
Alva and Alberta Pilliod say they used Roundup for more than 30 years to landscape their home and other properties.
They were both diagnosed with non-Hodgkin’s lymphoma.
A federal jury in San Francisco previously ordered the weed killer maker to pay a man $US80million, and a San Francisco jury in August awarded $US289million to a former greenskeeper, though a judge later reduced it.
The trials were the first of an estimated 13000 lawsuits against Monsanto.
St Louis-based Monsanto is owned by the German chemical giant Bayer, which said it would appeal the verdict.
‘‘The verdict in this trial has no impact on future cases and trials, as each one has its own factual and legal circumstances,’’ the company said.
The company noted that none of the California verdicts had been considered by an appeals court and that the US Environmental Protection Agency considers the weed killer safe.
The EPA reaffirmed its position in April, saying that the active ingredient glyphosate found in the weed killer posed ‘‘no risks of concern’’ for people exposed to it by any means — on farms, in yards and along roadsides, or as residue left on food crops.
The lawsuits have battered Bayer’s stock since it purchased Monsanto for $US63billion last year, and Bayer’s top managers are facing shareholders’ discontent.
Chairman Werner Wenning told shareholders at Bayer’s annual general meeting in Bonn last month that company leaders ‘‘very much regret’’ falls in its share price.
At the same time, chief executive officer Werner Baumann insisted ‘‘the acquisition of Monsanto was and remains the right move for Bayer’’.
Bayer’s stock price closed on May 13 at $US15.91 a share, down 45¢ , in trading on the New York Stock Exchange. The verdict was announced after the trading session closed.