Clewell HH 3rd, Gentry PR, Hack CE, Greene T, Clewell RA. An evaluation of the USEPA Proposed Approaches for applying a biologically based dose-response model in a risk assessment for perchlorate in drinking water. Regulatory toxicology and pharmacology. 2019 Jan 29. pii: S0273-2300(19)30036-4. doi: 10.1016/j.yrtph.2019.01.028.
The United States Environmental Protection Agency’s (USEPA) 2017 report, “Draft Report: Proposed Approaches to Inform the Derivation of a Maximum Contaminant Level Goal for Perchlorate in Drinking Water”, proposes novel approaches for deriving a Maximum Contaminant Level Goal (MCLG) for perchlorate using a biologically-based dose-response (BBDR) model. The USEPA (2017) BBDR model extends previously peer-reviewed perchlorate models to describe the relationship between perchlorate exposure and thyroid hormone levels during early pregnancy. Our evaluation focuses on two key elements of the USEPA (2017) report: the plausibility of BBDR model revisions to describe control of thyroid hormone production in early pregnancy and the basis for linking BBDR model results to neurodevelopmental outcomes. While the USEPA (2017) BBDR model represents a valuable research tool, the lack of supporting data for many of the model assumptions and parameters calls into question the fitness of the extended BBDR model to support quantitative analyses for regulatory decisions on perchlorate in drinking water. Until more data can be developed to address uncertainties in the current BBDR model, USEPA should continue to rely on the RfD recommended by the NAS (USEPA, 2005) when considering further regulatory action.
Lumen A, George NI. Evaluation of the risk of perchlorate exposure in a population of late-gestation pregnant women in the United States: Application of probabilistic biologically-based dose response modeling. Toxicology and applied pharmacology. 2017 Mar 2. pii: S0041-008X(17)30098-4. doi: 10.1016/j.taap.2017.02.021.
The risk of ubiquitous perchlorate exposure and the dose-response on thyroid hormone levels in pregnant women in the United States (U.S.) have yet to be characterized. In the current work, we integrated a previously developed perchlorate submodel into a recently developed population-based pregnancy model to predict reductions in maternal serum free thyroxine (fT4) levels for late-gestation pregnant women in the U.S. Our findings indicated no significant difference in geometric mean estimates of fT4 when perchlorate exposure from food only was compared to no perchlorate exposure. The reduction in maternal fT4 levels reached statistical significance when an added contribution from drinking water (i.e., 15μg/L, 20μg/L, or 24.5μg/L) was assumed in addition to the 90th percentile of food intake for pregnant women (0.198μg/kg/day). We determined that a daily intake of 0.45 to 0.50μg/kg/day of perchlorate was necessary to produce results that were significantly different than those obtained from no perchlorate exposure. Adjusting for this food intake dose, the relative source contribution of perchlorate from drinking water (or other non-dietary sources) was estimated to range from 0.25-0.3μg/kg/day. Assuming a drinking water intake rate of 0.033L/kg/day, the drinking water concentration allowance for perchlorate equates to 7.6-9.2μg/L. In summary, we have demonstrated the utility of a probabilistic biologically-based dose-response model for perchlorate risk assessment in a sensitive life-stage at a population level; however, there is a need for continued monitoring in regions of the U.S. where perchlorate exposure may be higher.
Erdemgil Y, Gözet T, Can Ö, Ünsal İ, Özpınar A. Perchlorate levels found in tap water collected from several cities in Turkey. Environmental Monitoring and Assessment. 2016 Mar;188(3):158. doi: 10.1007/s10661-016-5161-2.
Perchlorate is an inorganic anion that inhibits iodide transport to the thyroid by sodium-iodide transporters. Because perchlorate is highly soluble, stable, and mobile in water, drinking water is a potential source of perchlorate exposure. When exposed to perchlorate, thyroid dysfunction can be observed in sensitive populations (pregnant woman, infants, and children), especially those with iodide deficiency. The aim of this study was to determine the perchlorate levels in tap water from five cities in Turkey. Perchlorate concentrations of 145 tap water samples collected from Ankara, Isparta, Istanbul, Kayseri, and Sakarya were determined by liquid chromatography-tandem mass spectrometry. Mean and median values were found to be 0.15 and 0.07 μg/L, respectively. The median values (25-75 % percentile) of Istanbul, Ankara, Sakarya, Isparta, and Kayseri were 0.08 μg/L (0.04-0.09 μg/L), 0.07 μg/L (0.07-0.21 μg/L), 0.04 μg/L (0.04-0.04 μg/L), 0.03 μg/L (0.02-0.07 μg/L), and 0.25 μg/L (0.23-0.31 μg/L), respectively. The median perchlorate level observed in Kayseri was significantly higher than those found at other cities (p < 0.05). Perchlorate concentrations in water samples were lower than the interim drinking water health advisory level (15 μg/L) determined by the US Environmental Protection Agency. This study showed that perchlorate in drinking water is not the main source of exposure in these cities. Future studies should be performed to determine perchlorate levels in other potential sources, such as food products.
Desailloud R, Wemeau JL. [Should we fear the perchlorate ion in the environment?] Presse medicale (France) 2015 Nov 12. pii: S0755-4982(15)00443-1. doi: 10.1016/j.lpm.2015.10.002.
Perchlorate ions (ClO4–) are present in groundwater and are then present in distribution networks of drinking water destined for human consumption. The perchlorate ion comes mainly from ammonium salt manufactured for industrial activities or from arms of the First World War. Perchlorate ion is a competitive inhibitor of the sodium-iodide symporter and inhibits the synthesis of thyroid hormones. Values of toxicity have been published by the French agency ANSES and are used by authorities to limit the consumption of drinking water of some distribution networks by children and pregnant women especially in Nord-Pas-de-Calais and Picardie. Epidemiological data in other countries show no or little clinical effect in areas with similar contamination; it is therefore a precautionary principle. An effective substitution with iodine would limit the effects of the iodine deficiency itself but also would counteract the potential effects of an excess of perchlorate ions and also of other symporter inhibitors (thiocyanate, nitrate). Further studies are nevertheless needed to determine possible extra-thyroid effects of perchlorate ions.
Nir S, Brook I, Anavi Y, Ryskin M, Ben- Ari J, Shveky- Huterer R, Etkin H, Zadaka-Amir D, Shuali U. Water purification from perchlorate by a micelle–clay complex: Laboratory and pilot experiments. Applied Clay Science. Sep2015, Vol. 114, p151-156.
A technology for purification of water from perchlorate by filters including a complex between micelles of octadecyltrimethylammonium (ODTMA) and a clay-mineral, montmorillonite (Mt), or bentonite is presented. Laboratory filters of lengths of 20 and 40 cm were filled with a powdered micelle (ODTMA)–Mt complex mixed with excess sand at ratios of 1:100 to 1:15 w/w. A pilot filter (60 cm diameter ∙ 110 cm length) was filled with a 1:19 mixture. The complex exhibited a relatively large affinity to adsorb perchlorate; the presence of other anions, such as chloride, nitrate and sulfate at concentrations exceeding 1000-fold those of perchlorate had little effect on its removal from water by filtration. This high affinity was explained by the fact that the positively charged complex has abundance of hydrophobic regions, whereas perchlorate, is characterized by a large bare anionic radius, i.e., a loose hydration shell. A model which accounts for convection, adsorption and desorption was adequate in simulating and predicting the kinetics of filtration for two orders of magnitude variation in concentrations of perchlorate and one order of magnitude variations in concentrations of adsorbing sites, filter length, and flow velocities. Production of a granulated complex enabled to fill the filters exclusively with the complex and make the technology suitable for upscale. Based on the results of pilot experiments and model calculations, it is suggested that in comparison with other technologies, the micelle–clay filter has a relatively large capacity to remove perchlorate in the range of hundreds to thousands μg/l.
Song W, Gao B, Xu X, Zhang T, Chang L, Xin T, Shenglei S, Qinyan Y. Treatment of dissolved perchlorate by adsorption–microbial reduction. Chemical Engineering Journal 1 November 2015 279:522-529.
A novel method for perchlorate reduction by combination of adsorption and biological reduction was investigated in this work. After being adsorbed by biosorbent, the concentrated perchlorate was completely biologically reduced by mixed bacteria, which were dominated by Proteobacterial species. The reducing efficiency of perchlorate concentrated on biopolymer based adsorbent surface achieved optimal (75–85%) after 4days of reduction time in the neutral environment (pH: 7.0–7.5). The reduction of perchlorate was enhanced by the Cl− and SO42− ions and weakened by the dissolved NO3− ions in the reduction system. Moreover, per gram biopolymer based adsorbent could uptake 134.9 and 102.4mg of perchlorate in the first and second bio-regeneration cycles of column tests, with regeneration efficiency of 77.7% and 59.0%, respectively. In conclusion, results indicated that the reduction of concentrated perchlorate could be achieved simultaneously with the biosorbent bio-regeneration.
Nadaraja AV, Puthiyaveettil PG, Bhaskaran K. Surveillance of perchlorate in ground water, surface water and bottled water in Kerala, India. J Environ Health Sci Eng. 2015 Jul 28;13:56. doi: 10.1186/s40201-015-0213-z.
Background: Perchlorate is an emerging water contaminant that disrupts normal functioning of human thyroid gland and poses serious threat to health, especially for pregnant women, fetus and children.
Results: High level of perchlorate contamination in fresh water sources at places nearby ammonium perchlorate (rocket fuel) handled in bulk is reported in this study. Of 160 ground water samples analyzed from 27 locations in the State Kerala, 58 % had perchlorate above detection limit (2 μg/L) and the highest concentration observed was 7270 μg/L at Ernakulam district, this value is ~480 times higher than USEPA drinking water equivalent level (15 μg/L). Perchlorate was detected in all surface water samples analyzed (n = 10) and the highest value observed was 355 μg/L in Periyar river (a major river in the State). The bottled drinking water (n = 5) tested were free of perchlorate.
Conclusions: The present study underlines the need for frequent screening of water sources for perchlorate contamination around places the chemical is handled in bulk. It will help to avoid human exposure to high levels of perchlorate.