It's the pesticide on our dinner plates, a chemical so pervasive it's in the air we breathe, our water, our soil, and even found increasingly in our own bodies. Known as Monsanto's Roundup by consumers, and as glyphosate by scientists, the world's most popular weed killer is used everywhere from backyard gardens to golf courses to millions of acres of farmland. For decades it's been touted as safe enough to drink, but a growing body of evidence indicates just the opposite, with research tying the chemical to cancers and a host of other health threats.

In Whitewash, veteran...