Erinn Richmond collects aquatic invertebrates to test for pharmaceuticals in Brushy Creek in Churnside Park, Victoria, Australia. Source: Keralee BrowneErinn Richmond collects aquatic invertebrates to test for pharmaceuticals in Brushy Creek in Churnside Park, Victoria, Australia. Source: Keralee BrowneTo highlight the issue of pharmaceutical pollution affecting surface waters all over the world, a team of researchers conducted a study of stream insects, discovering the presence of 69 different pharmaceutical compounds — sometimes at concentrations threatening to the animals that feed on those insects.

Publishing their findings in the journal Nature Communications, the research team determined that the drugs pass through wastewater treatment facilities untreated and into the surface water where the stream insects gather. Once those insects emerge as flying adults, they pass traces of the drugs to bats, birds and spiders and then onto animals such as trout and platypus.

Emma Rosi, an aquatic ecologist at Cary Institute of Ecosystem Studies and a co-author on the paper, explained, "Stream life is swimming in a mixture of pharmaceuticals. Our study is the first to show that this chronic drug pollution can concentrate in aquatic insects and move up food webs, in some cases exposing top predators to therapeutically-relevant doses."

To reach that conclusion, the team took samples from six different streams in Melbourne, Australia, looking for 98 different pharmaceutical compounds including antibiotics, antidepressants, NSAIDs and antihistamines. Additionally, aquatic insects and riparian spiders were gathered.

"We focused on riparian spiders because they build their webs over streams and feed on adult aquatic insects as they emerge from the water," explained Erinn Richmond, a freshwater ecologist at Monash University in Australia and lead author on the study.

According to their findings, 69 different pharmaceutical compounds were discovered in the tissue of aquatic insects and 66 compounds were discovered in the riparian spiders," said co-author Jerker Fick, a chemist at Umeå University in Sweden who analyzed the samples. "Insect tissues had drug concentrations that were orders of magnitude higher than concentrations measured in surface waters. We also found a diverse suite of drugs in spiders, indicating that drugs are passed from the water to prey to predator, thereby exposing other animals in the food web to drugs."

"Pharmaceuticals were present in every insect and spider we tested — including those collected in Dandenong Ranges National Park," Richmond noted. "Even this seemingly pristine site was contaminated, likely because people live in the park's drainage area and visit the park."

In the locations investigated, platypus and brown trout consume the aquatic insects. As such, the team, basing its assumptions about the dietary habits of both platypus and trout, was able to estimate their exposure to the drugs.

"A platypus living in a creek receiving treated wastewater effluent could receive the equivalent of half of a recommended human dose of antidepressants every day — just by eating its normal diet of stream insects. This intake is likely to have biological effects," Rosi explained.

Among the insects tested during the study was the caddisfly, a common aquatic insect known in most parts of the world.

"Similar insects are found in freshwaters all over the world," Richmond said. "This isn't a problem specific to Australia; it's representative of what's likely happening wherever people take drugs. And it's likely an underestimate. We only tested for 98 pharmaceutical compounds — there are thousands in circulation."

Rosi concluded, "Pharmaceutical use is increasing worldwide. It's clear that the drugs we take are entering freshwaters and being passed up the food web. We don't know the ecological consequences of exposure to this pollution. What does it mean to be a platypus or trout with more than 60 drugs in your tissues? Are there synergistic effects? More research is needed on the extent of food web contamination and the effects of these compounds on fish and wildlife."

The research is published in the journal Nature Communications.

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