Shellfish Can’t Say No to Drugs
Unfortunately for them. But it is teaching scientists about the consequences of pharmaceutical pollution.
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From coastal cities around the world, through pipes lurking just beneath the waves, streams of human waste flood into the sea. Sometimes this water is cleaned—filtered, aerated, and treated with bleach. Sometimes it is not, and the reams of sewage—whatever we wash down the drain or flush down the toilet—flow into the ocean raw. If that grosses you out, consider that human excrement is probably the least crappy component of the flow, at least when it comes to environmental impacts. More troubling are certain invisible substances that easily pass through wastewater treatment plants and end up in the ocean.
Every Advil you pop or antidepressant you swallow is processed in your body and excreted, often as chemical byproducts that can still affect other organisms. Scientists have only tested a fraction of pharmaceuticals for their effects on marine life, and most remain unregulated in wastewater.
In their quest to understand the effects of drugs on marine life, however, scientists have found an involuntary ally: shellfish. Because they live stationary lives, clams and mussels have been accidental test subjects in pharmaceutical pollution research. Now, these shellfish are helping sound the alarm about several common drugs and chemicals.
Off the shore of São Paulo, Brazil, a pipe releases mostly untreated sewage into Santos Bay. And as biologist Fabio Pusceddu of the University of São Paulo reports in a recent study, the animals around this outfall appear to be feeling the effects of our drugs.
Recent studies have raised concerns about substances making it into the environment, including antibiotics in soaps and personal care products, estrogen mimics in birth control, and painkillers, but there’s not much data on the effects of these compounds on wildlife. So, Pusceddu grew shellfish in the lab on sediment contaminated with two drugs, exposing them to the same concentrations they face in Santos Bay.
One was ibuprofen, a common painkiller, and the other was triclosan, an antibacterial compound found in products including toothpastes and body washes. The drug exposure caused a range of negative effects, including malformed membranes and reproductive difficulties. This is a problem, Pusceddu says, because most toxicity assessments done by governments to see if a substance should be regulated only look at acute effects, which usually means whether the compound is lethal. But just because animals are surviving our pharmaceutical pollution doesn’t mean they are unaffected. Studies of chronic impacts from longer-term exposure are expensive and time-consuming, but it’s exactly these impacts that worry Pusceddu.
“We’re not talking about issues in one individual,” Pusceddu says, “but in a population in the long term.”
Coastal environments vary widely from city to city. São Paulo’s sewage lingers in sheltered Santos Bay, amplifying the effects of drug exposure. But on Canada’s west coast, deep water, dynamic tides, and strong currents routinely flush the Juan de Fuca Strait, where the city of Victoria, British Columbia, and surrounding municipalities have been pumping raw sewage through only a coarse screen since the 1960s. Regional wastewater officials, however, are worried about pharmaceuticals and began routinely monitoring the outfalls for drugs in 2004.
In a recent study, Chris Lowe, program manager with the Wastewater and Marine Environment Program for the Victoria region, showed that shellfish, sediment, and water in the region immediately around sewage outfalls show traces of drugs, including triclosan and ibuprofen. Lowe’s study only looked in detail at a dozen drugs, but he and his colleagues have detected many more.
So what does this outpouring of pharmaceutical waste mean for ocean life? Unlike heavy metals, most drugs don’t accumulate up the food chain. Though some compounds, such as triclosan, can build up in animal fat. But since drugs are designed to be effective at low doses, a little can do a lot of potential damage.
As of yet, there’s no widely used technology to target drugs. The only way these compounds are removed from sewage is if they bind to particles that are otherwise filtered out by standard treatments or if they break down naturally. Some researchers are developing systems that can be added to treatment plants to filter out pharmaceuticals, such as activated carbon filters or bacteria specifically designed to break down drugs. But these are still in development, and many drugs escape even the most advanced treatment plants currently operating.
Pusceddu says the effects of pharmaceutical waste vary by location and solutions should, too. In Brazil, for example, ibuprofen often comes in large packages, so people may flush a lot of expired medication. In this case, the solution may be to try to get manufacturers to make smaller packages. But ultimately, Pusceddu says we need to learn a lot more about what these compounds do in the environment. Only then can we tell if the drugs that keep us healthy are making the ocean sick.