"Here we review a small part of the rapidly growing scientific literature that raises questions about how ENMs might affect soil health and soil biodiversity in field trials and subsequently the commercial and chronic application of ENMs in agricultural soil. The questions concern not only the intentional use of ENMs in fertilizers, but the incidental presence of ENMs in “biosolids,” defined by the U.S. Environmental Protection Agency (EPA) as “treated residuals from wastewater treatment that can be used beneficially.”11 Biosolids are often used to fertilize agricultural fields. As a Purdue University researcher recently noted, “Land application of biosolids is standard procedure now [at least in the United States] . . . If any of that [biosolid] contains nanotubes, that could be a problem.”"