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Mood-changing drugs enter waterways, affect fish, study finds

Feb. 14, 2013
Courtesy of Umeå University, Science
and World Science staff


Some medicines that end up in the world’s wa­ter­ways af­ter be­ing used are af­fect­ing fish be­hav­ior, ac­cord­ing to a new stu­dy.

Tomas Brodin of Swe­den’s Umeå Uni­vers­ity and col­leagues found that wild Eu­ro­pe­an perch ate faster, be­came bolder and acted less so­cial af­ter ex­po­sure to an anxiety-moderating drug known as Ox­aze­pam.

Perch. (Courtesy Ben Christensen)


Residues of the drug of­ten wind up in nat­u­ral aquat­ic sys­tems af­ter peo­ple con­sume it, the re­search­ers said. They’re ex­cret­ed, flushed down the toi­let, trea­ted at wastewa­ter treat­ment plants, and end up in the wa­ter un­changed.

Brodin and col­leagues dosed wild perch with amounts of Ox­aze­pam equiv­a­lent to those found in Swe­den’s riv­ers and streams. Their re­sults, they said, sug­gested that even small amounts of the drug can al­ter the be­hav­ior and for­ag­ing ra­tes of these fish. 

“Nor­mally, perch are shy and hunt in schools. This is a known stra­tegy for sur­viv­al and growth. But those who swim in Ox­aze­pam be­came con­sid­erably bold­er,” said Brodin, lead au­thor of the re­port, pub­lished in the Feb. 15 is­sue of the jour­nal Sci­ence. The af­fect­ed fish left their schools to seek food on their own, a be­hav­ior that can be risky, he ex­plained; they al­so ate more quick­ly.

“We’re now go­ing to ex­am­ine what con­se­quenc­es this might have. In wa­ters where fish beg­in to eat more ef­fi­cient­ly, this can af­fect the com­po­si­tion of spe­cies, for ex­am­ple, and ultima­tely lead to un­ex­pected ef­fects, such as in­creased risk of al­gal bloom­ing,” said Brodin.

“The so­lu­tion to the prob­lem is not to stop med­i­cat­ing ill peo­ple but to try to de­vel­op sew­age treat­ment plants that can cap­ture en­vi­ron­men­tally haz­ard­ous drugs,” added en­vi­ron­men­tal chem­ist Jerk­er Fick, a co-au­thor of the stu­dy.

The sci­en­tists added that the find­ings should be seen as a point­er about what might be un­der­way in many wa­ters around the world, though full­er stud­ies are re­quired be­fore any far-reach­ing con­clu­sions can be drawn.


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Some medicines that end up in the world’s waterways after being used are affecting fish behavior, according to a new study. Tomas Brodin of Sweden’s Umeå University and colleagues found that wild European perch ate faster, became bolder and acted less social after exposure to an anxiety-moderating drug known as Oxazepam. Residues of the drug often wind up in natural aquatic systems after being consumed, the researchers said. They’re excreted, flushed down the toilet, treated at wastewater treatment plants, and end up in the water unchanged. Brodin and colleagues dosed wild perch with amounts of Oxazepam equivalent to those found in Sweden’s rivers and streams. Their results, they said, suggested that even small amounts of the drug can alter the behavior and foraging rates of these fish. “Normally, perch are shy and hunt in schools. This is a known strategy for survival and growth. But those who swim in Oxazepam became considerably bolder,” said Brodin, lead author of the report, published in the Feb. 15 issue of the journal Science. The affected fish left their schools to seek food on their own, a behavior that can be risky, he explained; they also ate more quickly. “We’re now going to examine what consequences this might have. In waters where fish begin to eat more efficiently, this can affect the composition of species, for example, and ultimately lead to unexpected effects, such as increased risk of algal blooming,” said Brodin. “The solution to the problem is not to stop medicating ill people but to try to develop sewage treatment plants that can capture environmentally hazardous drugs,” added environmental chemist Jerker Fick, a co-author of the study. The scientists added that the findings should be seen as a pointer about what might be underway in many waters around the world, though fuller studies are required before any far-reaching conclusions can be drawn. finds