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Assessing Waste Water Treatment Plant Effluent for Thyroid Hormone Disruption
Citation:
BURGESS, E. M., M. A. MILLS, AND M. W. HORNUNG. Assessing Waste Water Treatment Plant Effluent for Thyroid Hormone Disruption. Presented at SETAC North America 31st Annual Meeting, Portland, OR, November 07 - 11, 2010.
Impact/Purpose:
Much information has been coming to light on the estrogenic and androgenic activity of chemicals present in the waste water stream and in surface waters, but much less is known about the presence of chemicals with thyroid activity. To address this issue, we have utilized two assays to assess disruption of thyroid hormone (TH) synthesis and secretion by waste water treatment plant effluents. The first is an in vitro assay that measures the activity of thryoid peroxidase which is the enzyme involved in thyroid hormone synthesis, and the second uses a Xenopus laevis thyroid gland explant culture system that assesses the release of TH from thyroid glands in response to treatment with thyroid stimulating hormone (TSH). Effluent samples collected from two waste water treatment plants, one with primarily industrial inputs and one with primarily domestic and residential use inputs, were freeze dried and the resultant powder was reconstituted for testing in these assays. The enzyme inhibition assay and explant culture assays were shown to be adaptable to testing environmental samples. While the reconstituted effluent did not inhibit thyroid peroxidase activity in vitro, it did decrease the TSH-stimulated TH release from the thyroid glands. Analysis of the effluents for nitrate and ammonia showed high parts per billion to low parts per million concentrations of each, which may contribute to the reduced thyroid hormone release. Nitrate is a known inhibitor of iodide uptake into thyroid glands which would lead to decreased TH synthesis and release. Whether the concentration of nitrate, ammonia, or some other as yet unknown factor in these samples is sufficient to explain the decreased thyroid hormone release will need to be determined. These in vitro assays are promising tools to be further developed to identify the presence of thyroid disrupting activity in environmental samples and can be integrated with analytical chemistry methods for identification of any thyroid disrupting chemicals.
Description:
Much information has been coming to light on the estrogenic and androgenic activity of chemicals present in the waste water stream and in surface waters, but much less is known about the presence of chemicals with thyroid activity. To address this issue, we have utilized two assays to assess disruption of thyroid hormone (TH) synthesis and secretion by waste water treatment plant effluents. The first is an in vitro assay that measures the activity of thryoid peroxidase which is the enzyme involved in thyroid hormone synthesis, and the second uses a Xenopus laevis thyroid gland explant culture system that assesses the release of TH from thyroid glands in response to treatment with thyroid stimulating hormone (TSH). Effluent samples collected from two waste water treatment plants, one with primarily industrial inputs and one with primarily domestic and residential use inputs, were freeze dried and the resultant powder was reconstituted for testing in these assays. The enzyme inhibition assay and explant culture assays were shown to be adaptable to testing environmental samples. While the reconstituted effluent did not inhibit thyroid peroxidase activity in vitro, it did decrease the TSH-stimulated TH release from the thyroid glands. Analysis of the effluents for nitrate and ammonia showed high parts per billion to low parts per million concentrations of each, which may contribute to the reduced thyroid hormone release. Nitrate is a known inhibitor of iodide uptake into thyroid glands which would lead to decreased TH synthesis and release. Whether the concentration of nitrate, ammonia, or some other as yet unknown factor in these samples is sufficient to explain the decreased thyroid hormone release will need to be determined. These in vitro assays are promising tools to be further developed to identify the presence of thyroid disrupting activity in environmental samples and can be integrated with analytical chemistry methods for identification of any thyroid disrupting chemicals.