Thyroid hormone disrupting activities associated with phthalate esters in water sources from Yangtze River Delta

Thyroid hormone disrupting compounds in water sources is a concern. Thyroid hormone (TH) agonist and antagonist activities of water sources from the Yangtze River, Huaihe River, Taihu Lake and ground water in the Yangtze River Delta region were evaluated by use of a TH reporter gene assay based on the green monkey kidney fibroblast (CV-1). While weak TH receptor (TR) agonist potency was observed in only one of 15 water sources, antagonist potency was present in most of the water sources. TR antagonist equivalents could be explained by the presence of dibutyl phthalate (DBP), with concentrations ranging from 2.8 × 101 to 1.6 × 103 μg DBP /L (ATR-EQ50s). None of the ground waters exhibited TH agonist potencies while all of the samples from Taihu Lake displayed notable TR antagonist potencies. To identify the responsible thyroid active compounds, instrumental analysis was conducted to measure a list of potential thyroid-disrupting chemicals, including organochlorine (OC) pesticides and phthalate esters. Combining the results of the instrumental analysis with those of the bioassay, DBP was determined to account for 17% to 144% of ATR-EQ50s in water sources. Furthermore, ATR-EQ20–80 ranges for TR antagonist activities indicated that samples from locations WX-1 and WX-2 posed the greatest health concern and the associated uncertainty may warrant further investigation.

Research highlights
► We detected the thyroid hormone (TH) agonist and antagonist activities of water sources from the Yangtze River Delta.
► We found that TR antagonist activities were very common in water sources in this region.
► Combining the results of the instrumental analysis with those of the bioassay, dibutyl phthalate (DBP) was determined to account for most of the antagonist equivalents in water sources.
► For the very first time, REP20–80 ranges for TR antagonist activities were employed for comparative purposes.