During the last five decades environmental health researchers have documented environmental pollution’s profound impact on human bodies, including how human bodies bioaccumulate industrial chemicals and how those toxicants contribute to cancers and other chronic ailments. However, the relationship between toxicants and disease is often difficult to discern in mainstream sources of medical information. Previous research has identified the way print media systematically obscures the environmental causation frame in favor of a genetic and lifestyle frame. However, less has been said about medical publishing websites, which have become very influential. To address this gap I analyze WebMD’s coverage of leukemia, whose development is linked to over twenty toxicants. Similar to the print media research, I found WebMD’s coverage systematically obscures the environmental causation frame by failing to identify most toxicants associated with leukemia and by emphasizing a genetic and lifestyle causation frame. Building on previous research, I also identify rhetorical devices through which WebMD further downplays the environmental causation frame. As well, I discuss public health implications and sources of the problem.