It is embryo- toxic to frogs, a species that is an indicator of ecosystem health. It is lethal to yellow perch at actual application rates, which raises concern about toxicity in other fish species. Indeed, fisherman's groups like B.A.I.T. in Texas have led the fight against herbicides in their regions. Diquat binds with the lake bottom sediments and can persist there for years. After application into water, it breaks down into other chemicals, through sunlight and metabolism.
Residues drift far beyond the permit's inadequate one-quarter mile limit.
Overall, a vast body of important scientific literature challenges the safety of herbicides, although risk and benefit analyses in science are inherently uncertain. Eutrophication, which contributes to algae growth, cannot be controlled with herbicides. Multiple treatments can cause residual copper to accumulate in drinking water, as was recently observed in the New York City watershed. Creative bi-state cooperation would help to overcome the annual drawdown problems. A deep mid-winter drawdown kills the weeds more effectively than poison, but petty local problems have prevented regular drawdowns.