Biochemical characterisation of landfill leachate toxicity in fish

Abstract: Deposition remains the most common form of waste disposal in many parts of the world. As a terminus of the products consumed in our society a landfill may contain virtually all sorts of man-made chemicals. Despite this, the harmfulness of landfill leachate has not been extensively evaluated in feral organisms in the environment. In a leachate-contaminated lake, Molnbyggen, in Sweden, our studies reported a low percent of sexually mature (SM) female perch (Perca fluviatilis) that had decreased plasma androgen levels, decreased brain aromatase activity, distinctive sores and fin erosion. The impairments were attributed to unidentified compound(s) present in the leachate. In one out of four other investigated leachate-contaminated lakes, the low percent of SM female perch had reduced plasma sex steroid levels and similar sores as perch in Molnbyggen. The biochemical mechanism causing the disorders was investigated in order to establish a connection between the impairments and possible causative compound(s). Plasma levels of progesterone and 17α-hydroxyprogesterone were unaffected. Ovarian 17,20-lyase activity was decreased while levels of biliary steroid conjugates and hepatic testosterone UDP-glucuronosyltransferase activity did not differ between exposed and reference SM fish. Furthermore, the decreased brain aromatase activity seems to be a secondary effect; possibly a result of low substrate availability. Altogether, this suggests a possible disruption in the synthesis of androgens, knowledge that could be used as a tool in biomarker-directed fractionation studies to pinpoint compound(s). Molnbyggen sediment extracts decreased the testosterone and estradiol concentrations in whole-body homogenates of zebrafish (Danio rerio) after a three week exposure period. This suggests that compound(s) with the potency to alter endocrine function are present in the sediment. Although the first steps have been taken towards identifying compound(s) responsible for this kind of reproductive impairments, they still remain unidentified. Measures have to be taken to identify harmful chemicals in our society, to reduce their number, and to minimise their uncontrolled dispersal.