In First, Study Links 'Intersex' Fish with Drug Plant Contamination

Gobio gobio (the most common type of 'gudgeon')

A group of European researchers (Sanchez et al) report finding that up to 80% of  bottom-dwelling fish species– a group commonly called gudgeons *– living downstream of a pharmaceutical plant had mixed male and female characteristics in their sex organs.

Previous to this study, fish anglers on the river had noticed and reported swollen bellies and abnormal internal organs in some of the fish they had caught. Several researchers from French science laboratories were intrigued by these reports and decided to conduct a more scientific study.

Sample fish were collected (via electroshock) once in 2008 and once again in 2009 from three sites along the Dore River in France. One site, cite A, was used as a reference site and was upstream of the drug plant but downstream of a sewage treatment facility. A second site, site B, was located just downstream of the pharmaceutical plant (but above a second sewage plant), with a third site, site C,  more distantly downstream.

Data analysis from the 2008 samples found that over three quarters of the gudgeon fish (downstream of the plant) were “intersex”, that is , females exhibited male sex traits in their ovaries and males showed female traits in their testes. Such inter mixing of sex traits indicates endocrine disruption which can potentially reduce breeding capabilities, which in turn can impact the population as a whole as well as the population of other aquatic species (which either eat, or are eaten by, the declining species).

This finding in the downstream (site B) fish samples was dramatically contrasted with those sampled from upstream (site A) of the plant — finding only 5% of the samples being intersex.

The finding from the second year samples (2009) were consistent, though somewhat lower, showing 55% of the fish at site B were intersex, compared to only 8% from site A. This may indicate that the endocrine disrupting effects (from first exposure) diminish partially with time.

As to the most distant, sampled location, site C, the researchers found that 56% of the gudgeon fish were intersex, in 2008, and 44% in 2009. This result showed that the intersex effect persisted far from the (presumed) point of origin.

One other interesting finding here was that the sex organ abnormalities coincided with a general decline in the female fish population at sites B and C. Although several types of biomarker assays were conducted, the researchers will only hypothesize “‘contamination of investigated stream by a mixture of pollutants.”, that is, something in the water  is probably masculinizing the females, thought they do not suggest the actual agent(s) of this effect.

Still, the study is the first of its kind to link discharge from a pharmaceutical plant (as opposed to a sewage treatment facility) to biological changes in fish living downstream. Quoting the authors from the paper abstract:

“This evidence supports the hypothesis that pharmaceutical compounds discharged in stream are involved in recorded endocrine disruption effects and fish population disturbances and threaten disappearance of resident fish species.”

The researchers also assert their data warrants “an effect-based monitoring approach to assess impacts of pharmaceutical manufacture discharges on wild fish populations.”

Pharmaceuticals and their residues (partially broken down chemical compounds) can enter waterways indirectly via sewage treatment plants (after the chemical have been excreted, or, unused drugs are flushed down the toilet) or via direct discharge into streams and rivers from drug manufacturing plants. Exposure to these chemical mixtures may be contributing to the sex abnormalities, report the researchers.

The study helps determine the relative contributions from these two sources of chemicals.

The researchers also analyzed two other factors — species abundance and diversity — to determine whether there were any site-specific impacts on this and other fish populations.

A summary of those results:

Sites B and C  (those downstream from the plant) had fewer fish (177 and 74, respectively), whereas site A had 301 fish. Sites B and C also showed decreased fish species diversity (6 and 3 species, respectively), whereas site A had 8 species of fish. There later result may indicate some persistent (and distant) effect on ecosystem diversity.

* The most common type of gudgeon is Gobio gobio (also called ‘gobies’). This is a rheophilic (river-loving) and schooling species that occurs both in riverine and lacustrine (lake) habitats across continental Europe and the UK.

The results form the two year study were published in the June 30, 2001 edition of Environment International (vol. 37) under the title: Adverse effects in wild fish living downstream from pharmaceutical manufacture discharges.

Researchers (from several French research institutes) participating in this study were: Sanchez, W, W Sremski, B Piccini, O Palluel, E Maillot-Maréchal, S Betoulle, A Jaffal, S Aït-Aïssa, F Brion, E Thybaud, N Hinfray and JM Porcher.

Here is the paper abstract in full:

A set of biochemical and histological responses was measured in wild gudgeon collected upstream and downstream of urban and pharmaceutical manufacture effluents. These individual end-points were associated to fish assemblage characterisation. Responses of biotransformation enzymes, neurotoxicity and endocrine disruption biomarkers revealed contamination of investigated stream by a mixture of pollutants. Fish from sampled sites downstream of the industrial effluent exhibited also strong signs of endocrine disruption including vitellogenin induction, intersex and male-biased sex-ratio. These individual effects were associated to a decrease of density and a lack of sensitive fish species. This evidence supports the hypothesis that pharmaceutical compounds discharged in stream are involved in recorded endocrine disruption effects and fish population disturbances and threaten disappearance of resident fish species. Overall, this study gives argument for the utilisation of an effect-based monitoring approach to assess impacts of pharmaceutical manufacture discharges on wild fish populations.

Original reference article for this post:

Gender-bent fish found downstream of pharmaceutical plants by Tamara Tai

Author comment:

It is interesting that the decline in female fish, and/or the increase in “masculinized” females, presumably resulting from the disruption of the endocrine systems, would seem to indicate the presence of an androgen-like compound (male sex hormone) in the water, although the researchers say a “lack of sensitive fish species”, which could mean sensitivity to either male or female sex hormones.

A few earlier studies from the U.S. have identified “estrogen-like” compounds in waterways, believed to be disrupting reproductive cycles of female fish and altering sex organs in males.

Although this is a compelling study (showing a strong correlation [“link”] between likely exposure location and development of sex organ abnormalities), it is not definitive. The sample sizes are decent, but relatively small. No doubt follow up research on this case study is underway (or should be, soon). Hopefully, the fish organ tissue is being chemically analyzed.  At that point, it must then be shown that the given chemical(s) cause(s) — or could likely cause — the abnormalities found in the fish (and, in higher rates than the background abnormality rate for that region/species).

Once this occurs, and the chemical(s) are identified as being most likely synthetic (not likely to end up in water via natural processes), a determination must be made as to whether the chemical source (or derived metabolite of any chemical)  is the pharmaceutical plant in question.

This closes the causal chain loop. The process by which this happens could take another 3-4 years (not counting any legal challenges put forth by the drug plant).

Photo: Michal Maňas (User:snek01) ; CC – BY – SA 2.5

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