With businesses under pressure to act, solutions are emerging, but not fast enough, some participants fear.
The brain-harming metal is discharged directly into the river and carried to it on air currents. Some argue authorities are doing too little to stop both routes of pollution.
EHN.org investigation finds regulatory push to discredit independent evidence of harm while favoring pro-industry science despite significant shortcomings.
"The scary part is that most people who fish are not aware of these advisories although there are notices with fish and wildlife agencies"