RAB and others, My students and I did a study that has just been published on whether snails could slow the movement of PFOS through freshwater ecosystems. Snails are the basis of many local freshwater foodwebs, and we wanted to see if they would avoid PFOS. If they avoid sediments or algae with PFOS then this might slow the movement of PFOS in food webs. Our past work showed that the snails were incredibly sensitive to heavy metal mining pollution and would avoid the metals at concentrations of parts per billion. Unfortunately not so with PFOS. The snails avoid PFOS but only at concentrations much higher than levels that are already causing harm to humans. Many waterways have harmful PFOS levels below the snails' detection limits. I've attached the paper. Hugh Lefcort Hugh Lefcort Professor Biology Department, Gonzaga University Affiliate Professor University of Haifa, Israel