Walmart, which sells roughly 25% of all groceries in the United States, has reportedly begun selling unlabeled genetically engineered sweet corn produced by Monsanto.

The company is disregarding the concerns of consumer groups and environmentalists who say the product may not be safe for human consumption.

Sign the Open Letter Today! (will open on Corporate Action Network site)

Adding to the concern is the fact that Monsanto’s genetically engineered corn contains Bt toxin, a pesticide.

Monsanto claims the toxins will break down before the corn can be consumed by humans. Skeptics have questioned the company’s safety claims and a number of major groceries have said they won’t sell the corn.

Despite these concerns, Walmart says it will carry the product, without any special labeling.

Sign the Open Letter Today! (will open on Corporate Action Network site)

In the upcoming election, California voters have the opportunity to approve Proposition 37, which requires clear labels to let consumers know when foods are genetically modified.

Marissa Mayer, the recently named CEO of Yahoo! and Jim Breyer, a Board Member and major investor at Facebook, are leaders in Silicon Valley – an industry which prides itself on openness and information sharing.

Both Ms. Mayer and Mr. Breyer are also members of the Board of Directors of Walmart – a company that is eroding Californian’s right-to-know.     We are asking Ms. Mayer and Mr. Breyer to support Proposition 37 and to use their power as Walmart Directors to ensure that Walmart fully supports our right-to-know.

Sign the Open Letter Today! (will open on Corporate Action Network site)