Antidepressants that people take are building up in the brains of fish like walleye, bass, and perch. Researchers studied fish from the Niagara River, which connects lakes Erie and Ontario.
Scientists have known that a lot of the drugs we take end up in wastewater treatment plants, which aren’t designed to filter drugs out of the water.
Then fish take the drugs in.
Diana Aga is a professor of chemistry at the University at Buffalo College of Arts and Sciences, and she’s an author of a study in the journal Environmental Science & Technology. She says it appears fish can absorb the drugs two ways: through their gills and also by eating smaller fish.
"As they are swimming in the water, the water is constantly receiving effluent from wastewater treatment plants, so there's a constant input, so through the gills, they accumulate this," she says.
Aga says she and her team have two theories on how antidepressants then end up in fish brains.
“One [theory] is just accumulation because [antidepressants] are a little bit hydrophobic, which means they don’t like water, so they like fat. So, a brain has a lot of fat. The other theory we have is [antidepressants are] getting there by receptors. The way these antidepressants work on people’s brains, they are receptors that target the brain itself,” says Aga.
The study found that levels of the drugs in the fish brains are high enough to potentially affect the fish.
Aga says previous laboratory studies suggest antidepressants can affect a fish's ability to find food and escape predators.
“In various ways, some of [the antidepressants] could affect [the fish's] feeding behavior, because some of them could actually decrease the serotonin levels in fish which decreases their ability to capture prey,” says Aga.
“There have been some studies when the fish are exposed to these active ingredients, they tend to swim towards light, which could mean that they might not be able to recognize predators. So that could affect fish populations and biodiversity, depending on how much, how sensitive the fish are, because every species might behave and might be affected differently by these chemicals," says Aga.
But at this point, Aga says it's unlikely that there are any health risks for people who eat these fish.
“The levels are low enough to not affect humans, and also most of the time, the consumers don’t really eat liver or brain or gonads, so really we tend to remove all those, and then the levels in the muscles [are] very low,” she says.
Aga says she's currently working with fish biologists and toxicologists to find out the minimum levels of these drugs that can affect fish, and working with engineers to find effective ways to minimize pharmaceuticals in wastewater effluent.