Science Interviews

Oestrogen in the Water

Diana -  Professor Karen Kidd from the University of New Brunswick studies what effect oestrogen-like chemicals have on populations of fish.  Hello.

Karen -   Hello.

Diana -   Good to have you on this show with us, Karen.  Where do these hormones, like oestrogen, come from?

Karen -   Well, they're excreted by women.  We excrete a number of natural oestrogens and we also excrete the oestrogen that’s used in the birth control pill.  So, these oestrogens are going into our municipal waste water works or treatment works, and not being completely broken down in the treatment process.  And we’re finding very low, but effective concentrations of the oestrogens in the waters being discharged into our rivers.

Diana -   Once the oestrogens are in the water, what kind of effect can they have on the wildlife in there, on the fish?

Karen -   Well, we know from a great body of work that’s been done in the UK that these oestrogens are very effective at impacting or impairing reproduction in fish.  In particular, there were a number of studies showing that male fish living downstream of these discharges were becoming feminised - and when I say feminised, I mean the males were producing early stage eggs or producing egg proteins, or developing smaller gonads, and there was a great deal of detective work to try and figure out what it was in the river waters that was causing this feminisation.  These researchers at Exeter and Brunel and the EPA discovered that it was indeed these natural and synthetic oestrogens that women were excreting that was causing the feminisation in the male fish.

Diana -   So this wasn’t just affecting juvenile fish.  This was affecting adult male fish.

Karen -   Yes.  It was impairing their ability to produce sperm and to fertilise eggs.  It was also changing their external maleness, so they were less macho-looking, I guess you would say.

Diana -   So, what was the effect on this particular species of fish and then other fish that perhaps fed on them?

Karen -   Well, one of the questions that was outstanding was, what does it mean to have feminised male fish in the population?  And there have been a number of studies since then  - that work in the UK really motivated a lot of work in North America as well - where we found male fish in a number of our rivers that have become feminised because of the oestrogens.  But the big question that we wanted to answer with our study was; what does that mean to have feminised males in your population?  Can they still successfully reproduce or are you going to have fewer fish in the rivers because of this continuous low inputs of oestrogens and oestrogen mimics?

Diana -   So, how did you do your specific study?

Karen -   Well, there’s a research station in Canada.  It’s run by the federal government and it’s quite a unique facility because we have a series of lakes that we’ve set aside for research purposes.  So there’s no development in the watershed, there’s no commercial or sports fishing.  And what we can do is study the lake in its natural state for a few years and then add in chemicals or some other stressors and look specifically at what those stressors do to the ecosystem.  In this case, we did a whole lake experiment where we took the oestrogen that’s used in the birth control pill, we added it into the lake at levels that are very low, but what’s been measured in municipal waste waters, and then we followed how the fish responded at the biochemical level, at the tissue level, and the organism and population level.

Diana -   So you found obviously the male fish were becoming feminised.  So first of all, what happened to that species of fish where the males were becoming feminised and then what happened to the predator fish that ate them?

Karen -   Well, right away, the male fish in the lake started to respond to the oestrogen, so they started producing egg proteins then they developed early stage eggs.  And then only after two summers of additions of the oestrogen, we saw reproductive problems; the fat head minnow, which is a small-bodied fish in the lake, stopped reproducing and the numbers of individuals in the lake basically collapsed.  And so, we showed that it didn’t take very long for this very short-lived species to respond to small amounts of the oestrogen.  And then what was surprising to us was not just how quickly these fish responded to the oestrogen, but also the impacts that the loss of these fish species had on others in the lake.  In this case, what happened is the bigger predators in the lake, their numbers also started to decline, and it wasn’t because they were getting exposed to the oestrogens.  It was because the bigger fish were losing their prey species.  So, they're becoming skinnier and they stopped reproducing as a result.  This is showing us that you can have impacts of oestrogens on fish directly that interferes with their reproduction, but also, you can impact fish populations indirectly through the loss of their food source.

Diana -   So, once the population have gone into decline, what did you do then?  Did you remove the oestrogen and find out what would happen as soon as the levels went back to normal?

Tamara -   We did.  We added the oestrogen for three summers and then stopped, and followed the lake through recovery.  The first two summers after we stopped adding the oestrogen, the fat head minnow population numbers were still very low.  Then in the third year of recovery, they rebounded.  The numbers of fat head minnow in the lake were back to what they were before we started the experiment, and this was great news because, like in the case of bisphenol-A, it’s showing that once you remove the exposure, your effects go away basically.  So, there can be recovery in systems once you take oestrogens out.

Diana -   So they can recover very quickly, but what do you think the solution might be?  Currently, sewage works don't remove oestrogen from wastewater.  What do you think we could do to improve the situation?

Karen -   Well, they do remove quite a bit of oestrogens.  They know probably 80 to 90 percent of the oestrogens can be taken out when the wastewaters are treated with at least secondary treatment.  The challenge is that in some cases, there’s accidental overflow of systems when wastewater treatment works get overwhelmed with storm waters.  Some areas, there’s only very rudimentary treatment of wastewaters and it also seems to be more of a problem when river flow is made up primarily of wastewater discharge.  So, the more people you have along a river, the more municipal wastewater that’s being discharged, the greater the likelihood of impacting fish health from oestrogens is.  So, we do know that it can be removed and the more you treat it, the more effective you are at removing oestrogens from the wastewaters.

Diana -   Let’s hope it happens more all over the globe.  Thank you very much, Karen.  That was Professor Karen Kidd from the University of New Brunswick, explaining how chemicals that mimic the effects of hormones like oestrogen have an impact on aquatic ecosystems.

February 2010