Glyphosate, the main ingredient in Monsanto’s Roundup, is the most used herbicide on earth. From mass agriculture to backyard gardening, it is sprayed on most of the produce we cultivate. So much so, in fact, that a sampling of waterways in 38 states found glyphosate in the majority of rivers and streams tested. It was also found in about 70 percent of rainfall samples. Perhaps most disturbingly, some studies have even found elevated levels of glyphosate in American women’s breast milk.

For years, the Environmental Protection Agency deemed glyphosate non-harmful to humans. But now, an agency of the World Health Organization has declared that it “probably” causes cancer in people. And a new study found that Roundup’s other ingredients amplify the toxic effect on human cells—even at concentrations much more diluted than those used on farms and lawns.

In the wake of these studies, whole countries, like Sri Lanka, Brazil, Mexico and the Netherlands, are restricting or fully outlawing Roundup use. The U.S. has yet to do anything about it. But there is one American company that has declared its commitment to conscious consumer practices, and it should lead the charge in removing Roundup from its shelves.

Costco has stopped selling eggs from caged chickens, and worked hard to become the country’s largest retailer of organic foods. Let’s call on Costco to keep up the good work and remove dangerous Roundup from its retail inventory.

Costco’s CEO Jim Sinegal is known as a renegade among retail executives because of his diehard commitment to good corporate citizenship. From higher than average hourly wages and outstanding health benefits for workers, to careful selection of the products the store chooses to carry, Costco has risen above the crowd and shown the U.S. that it's fifth largest retailer can be successful and socially responsible all at once.

Jim Sinegal has another great chance to demonstrate his values by treating Roundup as the carcinogenic and environmentally disastrous toxin that it is. Please sign my petition asking Costco to discontinue the sale of Roundup in all of its stores.