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According to a new study, insects near watercourses absorb significant amounts of drugs and can transmit the compounds to predators located higher up the food chain, such as frogs, birds and bats.
"Predators that consume aquatic invertebrates in watercourses influenced by sewage can be exposed to about a quarter and up to half of a human dose of some pharmaceuticals", have writes the authors in the study published today in Nature Communications.
Pharmaceuticals are increasingly being detected in water courses around the world as prescription drug use increases. Drugs enter the water by people who excrete them or when they are thrown into the toilet. Wastewater treatment plants have not been designed to deal with such contamination and previous research has shown that only about half of the drugs are eliminated by sewage treatment.
This new study is the first to show that ubiquitous pharmaceutical pollution in the world's waters can focus on insects near rivers and up the food chain, potentially exposing major predators to "therapeutically relevant doses" Emma Rosi, Aquatic Ecologist at Cary Institute of Ecosystem Studies and co-author of the paper, told EHN.
The study has global implications, she added.
"We have known for a long time that pharmaceuticals are found in watercourses in areas like the Great Lakes and the United States," said Rosi. "If they are going into food networks in Australia, it should not be different here."
"Undeniably represents an underestimate"
Collection of aquatic invertebrates for pharmaceutical research purposes at Brushy Creek, Churnside Park, Victoria, Australia. (Credit: Keralee Browne)
Rosi and colleagues analyzed 98 drugs (including antibiotics, antidepressants and antihistamines) in Melbourne, Australia, and found 69 of them in aquatic insects and 67 in spiders.
"If you go to the doctor and tell them that you are taking a medicine, they want to know where there are intersections in your body," Rosi said. "We have found 69 different drugs in aquatic invertebrates ".
They found the highest levels in those tested downstream of wastewater treatment plants or densely populated areas – concentrations in these areas were 10 to 100 times higher than those at other sites.
"Insect concentrations in insect tissues were several orders of magnitude greater than those measured in surface waters," said co-author, Jerker Fick, a chemist at the University. of Umeå, Sweden, in a statement. "We also found a series of drugs in spiders, which indicates that drugs are passing water to prey predators, exposing other animals in the food web to drugs."
Rosi pointed out that riparian spiders build their canvases directly above watercourses. Thus, "the only way for them to take drugs, is when insects emerge from water courses in adulthood and are eaten by spiders".
The authors note that screening "undoubtedly represents an underestimation of the diversity of compounds present in food webs, because in the US market, for example, [more than] 1,400 pharmaceutical products approved by the Food and Drug Administration. "
By examining these concentrations and knowing the dietary habits of predators that eat creek insects, the researchers also estimated exposure to trout and platypus medications.
Rosi pointed out that it was not entirely clear if trout and platypus – and animals higher up the food chain like birds – would receive all the loading of pharmaceuticals if they ate insects. , simply because we do not yet fully understand the amount of drugs transmitted. when prey is consumed.
However, the charges could be significant, according to their estimates. A platypus, for example, could receive up to 50% of a dose of antidepressant administered to humans.
This intake is "likely to have biological effects," added Rosi.
"What does it mean to be a trout with more than 60 medications in your tissues?"
It is difficult to say what the effects of these exposures might be. Previous studies have shown that the presence of drugs in streams can disrupt the timing of insect emergence and affect the ability of spiders to weave their webs.
In fish, a lot depends on the drug, the mix and the dose; However, it has already been shown that pharmaceutical mixtures disrupt the endocrine system, feminize them, change behavior and reproduction, alter growth and increase the size of the liver.
There is less research on other wildlife such as birds, but a study earlier this year found that European starlings were less singles than females fed a fluoxetine-enriched worm diet – known as the commercial name of Prozac – at concentrations found during the treatment of wastewater facilities. Singing is a crucial part of the courtship and reproduction for birds and such behavioral changes could have effects on the population.
The researchers also noted that the use of pharmaceuticals is expected to continue to increase, particularly with the increase in the world's population.
Although conducted in Australia, the study has implications for water courses and wildlife everywhere. A lot of the study insects and all the drugs are found all over the world.
"What does it mean to be a platypus or a trout with more than 60 medications in your tissues – are there synergistic effects?" Said Rosi.
"We really do not know."
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