One of the most widely used herbicides in the U.S., Atrazine, is being reevaluated by the EPA. Some scientists say the weed killer negatively impacts the environment and human health. But Atrazine’s parent company Syngenta stands behind its product, claiming the nearly 6,000 studies, and the chemical’s 50-year use, are demonstrative of its safety. Living on Earth’s Jessica Ilyse Smith looks at the controversy surrounding EPA’s review of Atrazine.