Environmental Monitoring of Refuse Dump Leachate Toxicity in Fish

Sammanfattning: The global economy is driven by the consumption of goods and materials. Used products are often deposited on refuse dumps, making them potential point sources for all man-made chemicals. Water soaking through landfill waste results in a wastewater termed leachate. The collection and treatment of leachate is generally inadequate, but leachate toxicity is a surprisingly neglected area of research. This thesis covers six consecutive years (1996-2001) of environmental monitoring of toxicological effects and reproductive status in perch (Perca fluviatilis) from two Swedish lakes: Lake Molnbyggen, located within the same drainage area as a municipal refuse dump at Lindbodarna, and the reference Lake Djursjön. Toxicological and reproductive effects have been monitored also in fish from several other leachate-contaminated waters, including the stream Vadbäcken which drains the dump area and empties into Molnbyggen, and Lake Siljan, a recipient for the sewage treatment plant (STP) which processes some of the leachate from Lindbodarna. Unusually high frequencies of fin erosion and unique open body sores were found on Molnbyggen perch in 1996. They also had increased hepatic activities of catalase and glutathione-S-transferase. A weak induction of ethoxyresorufin O-deethylase (EROD) and low levels of DNA adducts indicated that the undersized gonads, observed in both sexes, were caused by pollutants specifically targeting gametogenesis. Later samplings revealed exceptionally low ratios of sexually mature (SM) females among both perch from Molnbyggen and brook trout (Salvelinus fontinalis) from Vadbäcken. Together with low gonadosomatic index (GSI), low brain aromatase (P450arom) activity, and low circulating levels of testosterone (T) and 17?-estradiol (E2) in both species, these results suggested a similar exposure to endocrine disrupting substances (EDSs) present in the refuse dump leachate. It was hypothesised that the aromatase activity could be inhibited by these EDSs, thereby disturbing the conversion of androgens into estrogens. An analysis of progesterone and 17?-hydroxyprogesterone indicated, however, that the low T levels in female perch and brook trout could result from a disturbance in its synthesis and that the low aromatase activity most likely was a result of down-regulation at the mRNA and/or protein level rather than a result of inhibition. In vitro studies of aromatase inhibition by chemical extracts of Molnbyggen sediments supported this conclusion. Mechanistic studies covering a single reproductive cycle further demonstrated that the disturbed synthesis of androgens could be a possible mechanism behind the reproductive failures, since too low T levels might be insufficient to activate the reproductive axis in leachate-exposed females. Analysis of 17?,20?-dihydroxy-4-pregnen-3-one (17?,20?-P) showed for the first time that it is the maturation-inducing hormone in this species. Three out of the four additional leachate-contaminated lakes investigated had low ratios of SM female perch. In Lake Nedre Vättern, the low ratio of SM females was associated with the same open body sores as in Molnbyggen, low GSI, low levels of T and E2, and high EROD activity, suggesting that the effects found in Molnbyggen and Vadbäcken are not unique. In Siljan, however, the low ratios of SM female perch found outside the STP were not associated with endocrine disruption. The EDSs responsible for the reproductive failures and endocrine disruption still remain unknown, thus the results of this thesis imply that the inappropriate handling of leachate from Swedish refuse dumps constitutes a serious environmental problem with unforeseeable consequences for wildlife and future generations.