Analysis of steroid hormones as endocrine disruptors in sewage, seawater and mussels using GC-MS techniques

Abstract

In recent years, there has been an increased concern over the appearance of endocrine dismpting chemicals (EDCs) in the aquatic environment due to their potential reproductive and early developmental toxicity to wildlife population. Municipal and industrial sewage effluents are considered as the major sources of EDCs. Among different classes of EDCs, natural and synthetic steroid estrogens have been identified as the most potent EDCs, as they can induce feminization in fish even at trace levels. Steroid hormones undergo extensive biodegradation during secondary treatment in municipal wastewater treatment processes. However, in Atlantic Canada only 50% of the population has municipal sewage treatment facilities. In many coastal towns and cities, including Halifax, Nova Scotia, and St. John's, Newfoundland & Labrador the raw sewage is directly discharged into harbours. Needless to say, sewage-related contaminants pose a serious threat to the marine ecosystem in these areas. -- Mussels are widely used to assess environmental impact of pollutants (metals and organics) in the marine environment. Mussels living near sewage outfalls may be exposed to constant levels of steroid estrogens through their food and respiration. This study examines whether these organisms can be used as a good bio-indicator for steroidal pollution. In this work, the analysis of steroid estrogens (estrone, estradiol, ethynylestradiol, diethylstilbestrol and mestranol) and fecal biomarker coprostanol in raw sewage, seawater and mussels collected from St. John's and Halifax harbours was undertaken. Two analytical methods based on GC- (ion trap) MS/MS were developed for mussel tissue and sewage analysis. A major factor in the success of method development was the removal of interferences of tissue matrix. Performance characteristics of these methods were evaluated using careful recovery experiments. Percentage recovery of analytes measured by spiking anaiyte standards in mussel and distilled water were >60% and >80% respectively. Reproducibility of the analytical methods calculated based on relative standard deviation values ranged from 7.7% to 13.3% for the analysis of mussel tissue and 3.0% to 6.8% for sewage effluents. This study reveals the presence of steroid estrogens estrone (E₁) and estradiol (E₂) and of high levels of coprostanol in seawater samples collected from both harbours indicating extensive fecal contamination and significant steroidal pollution. In addition, estrone (E₁) was measured in mussel samples obtained from some of the harbour locations. Concentration of coprostanol in mussels was used as a qualitative indicator of relative sewage contamination among the sampling sites. Further research should be undertaken to sample a larger number of mussel sites over a longer period to determine whether these organisms are reliable bio-indicators of steroidal pollution.