Perchlorate in sewage sludge, rice, bottled water and milk collected from different areas in China

Urinary perchlorate, thiocyanate, and nitrate and their associated risk factors among Chinese pregnant women

Perchlorate, nitrate, and thiocyanate are well-known inhibitors of iodide uptake and thyroid-disrupting chemicals. Widespread human exposure to them has been identified, whereas studies on their internal exposure levels among Chinese pregnant women are scarce and factors associated with them are not well recognized. The objective of this study is to determine their levels and identify the associated factors among pregnant women (n = 1120), based on a prospective birth cohort in Wuhan, central China, using repeated urine samples of three trimesters. Urinary perchlorate, thiocyanate, and nitrate were 100% detected in the samples, and specific gravity-adjusted median concentrations of them in all the samples were 12.6 ng/mL, 367 ng/mL, and 63.7 μg/mL, respectively. Their concentrations were weakly-to-moderately correlated with each other, with Spearman correlation coefficients ranging from 0.27 to 0.54. Poor reproducibility were observed for the three analytes over the three trimesters, with intraclass correlation coefficient of 0.07, 0.19, 0.04 for perchlorate, thiocyanate, and nitrate, respectively. The women who were overweight or used tap water as drinking water had significantly higher perchlorate concentrations, while those with excessive gestational weight gain had significantly higher thiocyanate concentrations (p < 0.05). The women with a college degree or above had lower nitrate concentrations (p < 0.05). Meanwhile, the median concentration of perchlorate in urine samples collected in spring, thiocyanate in those collected in winter, and nitrate in those collected in autumn, was significantly higher compared to their median concentrations in the samples collected in other three seasons (p < 0.05), respectively. Urinary perchlorate and nitrate concentrations of pregnant women in this study were higher than the concentrations of pregnant women in other countries, while thiocyanate concentrations were lower than that of most other countries. This study suggested potential covariates for future epidemiological analyses.

Perchlorate in fine particulate matter in Shenzhen, China, and implications for human inhalation exposure

The wide application of perchlorate in military and aerospace industries raises potential exposure risks for humans. Previous studies have mainly focused on perchlorate in drinking water, foodstuffs and dust, while its exposure in fine particulate matter (PM_2.5) has received less attention. Thus, we investigated its concentrations and temporal variability in PM_2.5 from October 2020 to September 2021 in Shenzhen, southern China. We also assessed the native population's intake and uptake of perchlorate in PM_2.5 via inhalation. Measured PM_2.5 concentrations in samples from Shenzhen ranged from 2.0 to 91.9 μg m^-3. According to air quality guidelines proposed by the World Health Organization, 12.7% of all the samples exceeded interim target 1 (> 35 μg m^-3), and only 37.3% met interim target 3 (< 15 μg m^-3). Logistic regression analysis showed that perchlorate concentrations positively correlated with the PM_2.5 concentrations and negatively correlated with precipitation. The median estimated daily intake (EDI) was highest for infants (0.029 ng kg^-1 day^-1), and both EDIs and estimated daily uptakes (EDUs) gradually decreased with age. All the EDIs and EDUs were below the reference dose provided by the US National Academy of Sciences (NAS), indicating that exposure to perchlorate in PM_2.5 posed negligible health risks for Shenzhen residents. However, the exposure of infants and specific groups who tend to be more highly exposed than average still warrants attention.

Environmental exposure to perchlorate, nitrate and thiocyanate, and thyroid function in Chinese adults: A community-based cross-sectional study

BACKGROUND

Evidence on environmental exposure to perchlorate, nitrate, and thiocyanate, three thyroidal sodium iodine symporter (NIS) inhibitors, and thyroid function in the Chinese population remains limited.

OBJECTIVE

To investigate the associations of environmental exposure to perchlorate, nitrate, and thiocyanate with markers of thyroid function in Chinese adults.

METHODS

A total of 2441 non-pregnant adults (mean age 50.4 years and 39.1% male) with a median urinary iodine of 180.1 μg/L from four communities in Shenzhen were included in this cross-sectional study. Urinary perchlorate, nitrate, thiocyanate, and thyroid profiles, including serum free thyroxine (FT4), total thyroxine (TT4), free triiodothyronine (FT3), total triiodothyronine (TT3), and thyroid stimulating hormone (TSH), were measured. Generalized linear model was applied to investigate the single-analyte associations. Weighted quantile sum (WQS) regression and Bayesian kernel machine regression (BKMR) models were used to examine the association between the co-occurrence of three anions and thyroid profile.

RESULTS

The median levels of urinary perchlorate, nitrate, and thiocyanate were 5.8 μg/g, 76.4 mg/g, and 274.1 μg/g, respectively. After adjusting for confounders, higher urinary perchlorate was associated with lower serum FT4, TT4, and TT3, and higher serum FT3 and TSH (all P < 0.05). Comparing extreme tertiles, subjects in the highest nitrate tertile had marginally elevated TT3 (β: 0.02, 95% CI: 0.00-0.04). Each 1-unit increase in log-transformed urinary thiocyanate was associated with a 0.04 (95% CI: 0.02-0.06) pmol/L decrease in serum FT3. The WQS indices were inversely associated with serum FT4, TT4, and FT3 (all P < 0.05). In the BKMR model, the mixture of three anions was inversely associated with serum FT4, TT4, and FT3.

CONCLUSIONS

Our study provides evidence that individual and combined environmental exposure to perchlorate, nitrate, and thiocyanate are associated with significant changes in thyroid function markers in the Chinese population with adequate iodine intake.

Health risk assessment of perchlorate and chlorate in red swamp crayfish (Procambarus clarkii) in China

Perchlorate and chlorate are both strong oxidants and thyroid toxicants that are widely distributed in soil, water and human foods. The red swamp crayfish (Procambarus clarkii) is a common aquatic organism that is popular in Chinese culinary dishes. Dietary intake is the main route of human exposure to perchlorate and chlorate, though the health risks of crayfish consumption are unknown. Thus, this study investigated the quantities of perchlorate and chlorate in red swap crayfish from sampling sites in five provinces located near the Yangtze River in China, along with the associated health risks of consuming this species. Perchlorate was detected in 55.6-100 % of crayfish samples in each sampling location, and chlorate was found in 100 % of samples cross all sites. Concentrations of perchlorate in crayfish from upstream provinces (Hubei, Hunan and Jiangxi) were higher than those from downstream provinces (Anhui and Jiangsu). Perchlorate and chlorate concentrations were positively correlated in crayfish, suggesting that chlorate may be a degradation byproduct of perchlorate. The quantities of both pollutants in hepatopancreas tissue were higher than in muscle tissues (p < 0.05), such that we do not recommend ingesting crayfish hepatopancreas. Hazard quotient (HQ) values for chlorate in crayfish were <1 across all provinces, suggesting no potential health risk of chlorate exposure through crayfish consumption. However, perchlorate concentrations in crayfish from the Jiangxi province had an associated HQ value >1, suggesting potential risks for human health. These results will be useful in informing mitigation measures aimed at reducing perchlorate exposure associated with crayfish consumption.

A nationwide investigation of perchlorate levels in staple foods from China: Implications for human exposure and risk assessment

Perchlorate is an emerging pollutant and thyroid toxicant frequently occurred in air, water, soil and various foodstuffs. Rice and wheat flour are the most common staple foods, which could accumulate perchlorate from contaminated soils and irrigation water. However, human exposure to perchlorate via rice and wheat flour consumption has only been investigated to a limited extent. Therefore, we collected 207 rice samples and 189 wheat flour samples from 19 provinces in China to assess the level of perchlorate. The levels of perchlorate in rice and wheat flour ranged from not detected (N.D.) to 28.7 ng/g and less than limits of quantification (<LOQ) to 147 ng/g, respectively, with detection rates in both rice and wheat flour samples exceeding 60 %. The estimated daily intake (EDI) and hazard quotient (HQ) were calculated to evaluate human exposure and potential health risk of perchlorate exposure via the consumption of rice and wheat flour. The HQ values for both rice and wheat flour were less than 1, which suggested that the consumption of these staple foods may not cause potential health risks. To our knowledge, this is the first nationwide monitoring, human exposure and risk assessment of perchlorate in both rice and wheat flour in China.

Presence of Chlorate and Perchlorate Residues in Raw Bovine Milk from Italian Farms

Chlorates and perchlorates are endocrine disruptors and emerging environmental contaminants found in various types of foods, including milk and dairy products. The presence of chlorate has been associated with the use of chlorine-based sanitizers to disinfect equipment and water used in food processing. Perchlorate, on the other hand, occurs naturally in the environment but is also released from anthropogenic sources. To protect consumers, the EU set an MRL for chlorate in milk but not for perchlorate. Considering that data on chlorates and perchlorates in this field are limited, the objective of this study was to assess the presence of these two anions in 148 samples of raw bovine milk collected from different farms of Lombardy and grouped in three different geographical zones. Chlorate was detected in 73% of the samples analyzed, at concentrations ranging from <LOQ to 18.70 μg kg−1 with an average value of 7.10 ± 5.88 μg kg−1 below the MRL; perchlorate with a frequency of 99%, in the range from <LOQ to 6.95 μg kg−1 and an average value of 4.06 ± 1.58 μg kg−1. No significant differences were detected among the three geographical zones. An evaluation of the estimated daily intake of perchlorate through milk confirmed the absence of risk for Italian consumers.

Determination of exposure to major iodide ion uptake inhibitors through drinking waters

Goiter, abnormal enlargement of the thyroid gland, is a significant worldwide public health problem. Iodine deficiency is known as the most common cause. Iodine is actively transported as iodide ion (I^-) using Sodium Iodide Symporter (NIS) and sufficient blocking of I^- transportation prevents the synthesis of thyroid hormones. The transportation can be blocked by some polyatomic anions known as I^- uptake inhibitors. Perchlorate (ClO₄^-), thiocyanate (SCN^-) and nitrate (NO₃^-) are reported as the major I^- uptake inhibitors and exposure could be through various routes. Drinking water is an important exposure route. Since water is essential to sustain life, drinking water safety is very important for the protection of public health. However, as a result of natural and human-based processes, water can be contaminated and contamination of drinking water is a global food safety problem due to causing significant health and environmental problemsIn that context, this study aims to determine exposure levels to I^- uptake inhibitors that arise from drinking waters at five different districts in Antalya, Turkey. Collected water samples contained NO₃^- and ClO₄^- in the range of 0.86-47.42 mg/L and <LOQ-0.11 mg/L, respectively. SCN^- levels were <LOQ in all samples. Daily exposure was calculated for different age groups of 2-65+ years using contaminant levels, water consumption and body weight data. Mean NO₃^- and ClO₄^- exposure levels were in the range of 115.89-375.06 and 0.07-0.22 μg/kg bw/d, respectively. Exposure levels were decreased with increasing age and the highest exposure levels were calculated for children due to their lower body weight. Although no risk was determined for the I^- uptake inhibitors in tested locations based on the guideline values recommended by EPA and WHO, there has been a need for more exposure assessment studies in the areas where the high prevalence of goiter is observed all over the world.

Determination of perchlorate and its distribution in unhusked rice in China

Perchlorate concentrations in 387 unhusked rice samples from 15 main producing provinces in China were investigated by HPLC–MS/MS. The results indicated that perchlorate displays a mean level of 17.17 μg/kg in unhusked rice samples. Intriguingly, we also found that perchlorate is mainly observed in rice husk among of these collected unhusked rice samples, while less observed in rice bran and milled rice. Specifically, the perchlorate levels in rice were found in the husks (73.61%), bran (10.09%) and milled rice (19.52%), respectively. Our results indicated that there is no significantly perchlorate exposure risk in edible milled rice. We suggested that perchlorate in rice can be greatly removed if deep processed unhusked rice and there is no perchlorate exposure risk in edible milled rice.

The risk of perchlorate and iodine on the incidence of thyroid tumors and nodular goiter: a case-control study in southeastern China

BACKGROUND

The incidence rates of thyroid tumors and nodular goiter show an upward trend worldwide. There are limited reports on the risk of perchlorate and iodine on thyroid tumors, but evidence from population studies is scarce, and their impact on thyroid function is still uncertain. Therefore, the objective of this study was to investigate the association of perchlorate and iodine with the risk of nodular goiter (NG), papillary thyroid microcarcinoma (PTMC), and papillary thyroid carcinoma (PTC) and to assess the correlation between perchlorate and iodine with thyroid function indicators.

METHODS

A case-control population consisting of 184 pairs of thyroid tumors and nodular goiter matched by gender and age (±2 years) was recruited in this study. Serum and urine samples were collected from each participant. Thyroid function indicators in serum were tested by automatic chemical immunofluorescence, and perchlorate and iodine levels in urine were determined by ultra-high performance liquid chromatography tandem-mass spectrometry and inductively coupled plasma-mass spectrometry, respectively. Conditional logistic regressions and multiple linear regressions were used to analyze the associations.

RESULTS

Urinary perchlorate concentration was significantly higher in total cases, NG and PTC than in the corresponding controls (P < 0.05). Perchlorate was positively associated with PTC (OR = 1.058, 95% CI: 1.009, 1.110) in a non-linear dose-response relationship, but there was no association between perchlorate and NG or PTMC. Iodine was not associated with the risk of thyroid tumors and NG and did not correlate with the thyroid function indicators. Furthermore, perchlorate showed a positive correlation with thyroid stimulating hormone (TSH) at iodine adequate levels (P < 0.05), and a negative correlation with free triiodothyronine (FT3) and a positive correlation with thyroglobulin antibody (TgAb) at iodine more than adequate or excess levels (P < 0.05).

CONCLUSIONS

Perchlorate can increase the risk of PTC in a non-linear dose-response relationship and disturb the thyroid hormone homeostasis and thyroid autoantibody levels.

Perchlorate occurrence, sub-basin contribution and risk hotspots for drinking water sources in China based on industrial agglomeration method

Perchlorate is a persistent inorganic contaminant which has attracted wide attention because of its harmful effects on physical health. Despite the potential adverse effects to humans via drinking water, related research at the national scale in China are scarce. In this study, the occurrence of perchlorate in major river basins in China was investigated from 2009 to 2020. Generally, except for the Yangtze River Basin, perchlorate concentrations in the surface water of other river basins were low, ranging from < 0.01 to 8.53 μg/L. The results of a specialized field sampling and tracking program in the Yangtze River Basin in 2019 showed that the Xiangjiang River basin is the greatest contributor of perchlorate in the Yangtze River Basin, accounting for 58.63% of the total perchlorate input. Furthermore, based on correlation analysis between production enterprise information and measured concentrations in sampled sites, fireworks and explosives production industries were identified as the major sources of perchlorate contamination in surface water. The risk map showed that the central-southern part of China and the central part of Xinjiang province were risk hotspots for perchlorate contamination. The results gave insights into how to conduct more precise risk assessment and policy intervention towards prevention of perchlorate contamination.

Perchlorate contamination of tea leaves and a corresponding probabilistic dietary risk assessment using Monte Carlo simulation

Perchlorate is known as a thyroid disrupter. Its contamination in various tea samples was monitored, and 286 samples belonging to four types of tea leaves were analysed. The detection rate of perchlorate in tea was 99.3%. The mean concentration in different tea types decreased in order from green tea, oolong tea, white tea to black tea. A probabilistic approach was performed to evaluate the dietary exposure of perchlorate for six different subpopulations. The daily intakes (EDIs) for consumers over the age of 41 were higher than that of other subpopulations. The hazard quotient for six groups was lower than 1 even at the extreme percentile (P99). It indicates that the risk of dietary exposure to perchlorate from tea consumption for Fujian people is acceptable without considering other foodstuffs. However, the high occurrence of perchlorate in tea samples suggested that the actual source of this contaminant should be further investigated.

Perchlorate in shellfish from South China Sea and implications for human exposure

Shellfish can absorb and accumulate contaminants. The consumption of shellfish could expose humans to pollutants and increase related health risk. Perchlorate (ClO₄^-) is a ubiquitous pollutant and could affect thyroid functions, especially for children and pregnant women. However, knowledge on the contamination of perchlorate in aquatic food such as shellfish remains limited. This study aimed to investigate the abundances of perchlorate in shellfish from South China Sea and to assess human exposure risks. A total of 178 shellfish samples from eight species were collected from offshore aquaculture waters in South China Sea. Perchlorate was detected in 99.4% of them, suggesting widespread pollution in coastal waters. Concentrations of perchlorate ranged from not detected (N.D.) to 71.5 μg kg^-1, with a median value of 4.33 μg kg^-1. Estimated daily intake (EDI) and hazard quotient (HQ) were used to assess human exposure dose and health risks, respectively. The HQ values were determined to be less than 1, indicating no significant health risks to local residents via shellfish consumption. To our knowledge, this is the first study to investigate perchlorate contamination in South China shellfish and assess potential human risks.

Perchlorate Levels in Polish Water Samples of Various Origin

Perchlorate ion (ClO4−) is known as a potent endocrine disruptor and exposure to this compound can result in serious health issues. It has been found in drinking water, swimming pools, and surface water in many countries, however, its occurrence in the environment is still poorly understood. The information on perchlorate contamination of Polish waters is very limited. The primary objective of this study was to assess ClO4− content in bottled, tap, river, and swimming pool water samples from different regions of Poland and provide some data on the presence of perchlorate. We have examined samples of bottled, river, municipal, and swimming pool water using the IC–CD (ion chromatography–conductivity detection) method. Limit of detection and limit of quantification were 0.43 µg/L and 1.42 µg/L, respectively, and they were both above the current health advisory levels in drinking water. The concentration of perchlorate were found to be 3.12 µg/L in one river water sample and from 6.38 to 8.14 µg/L in swimming pool water samples. Importantly, the level of perchlorate was below the limit of detection (LOD) in all bottled water samples. The results have shown that the determined perchlorate contamination in Polish drinking waters seems to be small, nevertheless, further studies are required on surface and river samples. The inexpensive, fast, and sensitive IC–CD method used in this study allowed for a reliable determination of perchlorate in the analyzed samples. To the best of our knowledge, there are no other studies seeking to assess the perchlorate content in Polish waters.

Study on the bioaccessibility and bioavailability of perchlorate in different food matrices in vitro

Perchlorate, a persistent pollutant, interferes with iodine uptake by the thyroid. Perchlorate exposure mainly occurs through ingested food; understanding the bioaccessibility and bioavailability of perchlorate in foods facilitate more accurate human health risk assessments. An in vitro digestion/Caco-2 cell model was used for this research. The bioaccessibility of perchlorate in the control group, lettuce, rice and formula was 93.45%, 70.14%, 70.25%, and 63.68%, respectively. The bioavailability of perchlorate was as follows: control group, 43.45%; rice, 37.17%; lettuce, 35.13%; and formula, 30.72%. The absorptive apparent permeability coefficient (Papp) of the control, lettuce, rice, and formula was 30-101 nm/s, 32-65 nm/s, 54-161 nm/s, and 41-88 nm/s, respectively. The results suggested that the risk from perchlorate was overestimated only when considering the content of perchlorate in foods and that the presence of food matrices reduced perchlorate bioavailability by differing degrees.

Accurate, sensitive and rapid determination of perchlorate in tea by hydrophilic interaction chromatography-tandem mass spectrometry

Perchlorate is an environmental contaminant interrupting thyroid hormone production, and perchlorate in tea has raised wide concern recently. In this study, an accurate method was developed for the determination of perchlorate in tea using hydrophilic interaction chromatography-tandem mass spectrometry and a simplified QuEChERS procedure. The method utilized a zwitterion HILIC column for separation, and the optimal gradient eluents consisted of acetonitrile and aqueous solution with 0.1% formic acid and 20 mmol L^-1 ammonium formate. Calibration curves were fitted by the quadratic model with 1/x weight instead of the linear model. As perchlorate was only partially extractable when using acetonitrile or methanol as the extraction solvent, acetonitrile/water (1 : 1, v/v) was chosen to extract perchlorate from tea samples. Graphitized carbon black was used as the dispersive solid phase extraction sorbent to clean up tea extracts. The method exhibited satisfactory accuracy with recoveries of 81.4-100.9% and relative standard deviations of 1.3-14.5% for green and black teas. The limit of quantitation was 0.005 mg kg^-1, while the limits of detection were 0.0011 mg kg^-1 for green tea and 0.0013 mg kg^-1 for black tea, indicating an excellent sensitivity of this method. A 100% positive rate of perchlorate was found in 100 real tea samples, and the concentrations ranged from 0.0030 mg kg^-1 to 0.78 mg kg^-1. This accurate, sensitive and rapid method would be suitable for monitoring, risk assessment and source identification of perchlorate in tea.

Surface-enhanced Raman scattering-based detection of hazardous chemicals in various phases and matrices with plasmonic nanostructures

Surface-enhanced Raman scattering (SERS)-based sensors utilize the electromagnetic-field enhancement of plasmonic substrates with the chemical specificity of vibrational Raman spectroscopy to identify trace amounts of a wide variety of different target analytes while being minimally affected by photobleaching. However, despite many advantageous features of this method, SERS sensors, particularly for detecting hazardous chemicals, suffer from several limitations such as requirement of gigantic signal enhancement that is often poorly controllable, subtle change and degradation of the SERS substrate, consecutive fluctuation of the signal, the lack of reliable receptors for capturing targets of interest and the absence of general principles for detecting various chemicals in different phases and matrices. To overcome these limitations and for SERS sensors to find practical use, one must (1) acknowledge the characteristics of the matrices of target systems, (2) finely engineer and tune the receptors of the SERS sensor to properly extract the target analyte from the phase, and (3) implement additional mechanistic modifications to enhance the plasmonic signal. This minireview underlines the difficulties associated with different phases and a wide range of target analytes, and introduces the practical measures undertaken to overcome the respective difficulties in SERS-based detection of hazardous chemicals.

One-step sample processing method for the determination of perchlorate in human urine, whole blood and breast milk using liquid chromatography tandem mass spectrometry

A one-step sample processing was developed to determine the levels of perchlorate in human urine, whole blood and breast milk by using liquid chromatography tandem mass spectrometry (LC-MS/MS). Athena C18-WP column was used to separate and analyze perchlorate. Perchlorate and isotope-labeled perchlorate (Cl¹⁸O₄^-) internal standards were spiked in the sample matrix through vortex mixing, centrifugation, and filtration. The filtrate was collected and subjected to LC analysis. The developed method was validated for its reproducibility, linearity, trueness, and recovery. Satisfactory recovery of perchlorate ranged from 81% to 117% with intraday relative standard deviations (RSDs) (n = 3) and inter-day RSDs (n = 9) of 5-18% and of 5-16%, respectively. Good linearity (R² ≥ 0.99) was observed. Limits of detection and quantification for perchlorate ranged from 0.06 µg/L to 0.3 µg/L and from 0.2 µg/L to 1 µg/L, respectively. Perchlorate concentrations were found in human urine (n = 38) and whole blood (n = 8) samples with the range of 6.5-288.6 µg/L and 0.3-2.8 µg/L, respectively. These results indicate the applicability of our developed method in determining perchlorate level in real samples. Moreover, this method is also highly reliable, sensitive and selective in detecting perchlorate in human urine, whole blood and breast milk samples and may be applicable to other matrixes i.e. saliva, serum, plasma, milk powder and dairy milk.

Evidence for Biotic Perchlorate Reduction in Naturally Perchlorate-Rich Sediments of Pilot Valley Basin, Utah

The presence of perchlorate on Mars suggests a possible energy source for sustaining microbial life. Perchlorate-reducing microbes have been isolated from perchlorate-contaminated soils and sediments on the Earth, but to date, never from an environment that is naturally enriched in perchlorate. The arid Pilot Valley paleolake basin in Utah is a Mars analog environment whose sediments are naturally enriched with up to ∼6.5 μg kg^-1 perchlorate oxyanions. Here, we present results of field and laboratory studies indicating that perchlorate-reducing microorganisms co-occur with this potential electron acceptor. Biogeochemical data suggest ongoing perchlorate reduction; phylogenetic data indicate the presence of diverse microbial communities; and laboratory enrichments using Pilot Valley sediments show that resident microbes can reduce perchlorate. This is the first article of the co-existence of perchlorate-reducing microbes in an environment where perchlorate occurs naturally, arguing for Pilot Valley's utility as an analog for studying biogeochemical processes that may have occurred, and may yet still be occurring, in ancient martian lacustrine sediments.

Worldwide occurrence and origin of perchlorate ion in waters: A review

Perchlorate (ClO₄^-) is a persistent water soluble oxyanion of growing environmental interest. Perchlorate contamination can be a health concern due to its ability to disrupt the use of iodine by the thyroid gland and the production of metabolic hormones. Its widespread presence in surface water and groundwater makes the aquatic environment a potential source of perchlorate exposure. However, the amount of published data on perchlorate origins and water contamination worldwide remains spatially limited. Here, we present an overview of research on perchlorate origins and occurrences in water, and the methodology to distinguish the different perchlorate sources based on isotope analysis. All published ranges of isotopic content in perchlorate from different sources are presented, including naturally occurring and man-made perchlorate source types, as well as the effects of isotope fractionation that accompanies biodegradation processes. An example of a case study in France is presented to emphasize the need for further research on this topic.

Reproductive toxicity of perchlorate in rats

Perchlorate, as an oxidizer, has many applications such as explosives and pyrotechnics, especially in rocket propellants and missile motors. Because it was found in water including wells and drinking water in the US, its effect on human health was being noted. However, the reproductive toxic effect on perchlorate is still unclear. In present study, the effects of repeated exposure to perchlorate on reproductive toxicity were evaluated in Wistar rats. The rats were treated orally with perchlorate at doses of 0.05, 1.00 or 10.00 mg/kg body weight (b.w.) daily for 8 weeks. The levels of T₃ and T₄ hormones in the rat serum were detected by radioimmunoassay kit. The indexes of reproduction, percentage of organ in body weight (%) and frequency of abnormal sperm cells were also analyzed in this study. DNA damage in testicular cells was evaluated by Comet assay. The levels of MDA, GSH and SOD were examined in testicle tissues of rats by ELISA. The expression of c-fos and fas protein was examined in testicle tissues by immunohistochemistry. The results showed that perchlorate did not affect the body weight of rats. Perchlorate also significantly decreased indexes of live birth and weaning in the groups of 1.00 and 10.00 mg/kg, and viability index only in the 10.00 mg/kg group (P < 0.05). Perchlorate also significantly decreased the serum level of T₃ in male rats of 1.00 and 10.00 mg/kg groups, increased the rate of sperm abnormality (10.00 mg/kg), potentially caused DNA damage in testicular cells and altered the status of oxidative stress in male rats. In addition, because of the increase in the expression of fas and c-fos protein in testicle tissues, perchlorate could induce apoptosis in spermatogenesis. Thus, these findings indicate that perchlorate could cause DNA damage in testicular tissues and reduce testicular spermatogenic ability, resulting in reproductive toxicity.

Analysis of perchlorate in baby food on Canadian (Ottawa) markets in 2009 and estimated dietary exposure

In order to determine the baseline levels of perchlorate in major brands of baby food, 200 baby food products were collected from retail stores in Ottawa, Canada and analysed for perchlorate in 2010. The seven food groups tested were fruit, juices, vegetables, meat, yogurt, mixed (vegetable mixed with meat) and other (e.g. vegetable mixed with meat and cereal, cheese, egg,). Samples were extracted with a mixture of methanol and 1% acetic acid (4:1, v/v). Determination was conducted by stable isotope dilution ion chromatography tandem mass spectrometry (ID-IC-MS/MS). The complexity of different food matrices required additional method validation. The perchlorate levels in 46 samples were found to be lower than the quantification limit (0.2 ng g^-1). The perchlorate levels in the other 154 baby food samples were also low; about 96.7% of the baby foods had perchlorate levels less than 10 ng g^-1 (ranged from 0.2 to 22.4 ng g^-1, median1.35 ng g^-1); only 5 samples had perchlorate levels higher than 10 ng g^-1. Dietary exposure to perchlorate from analysed baby food was conservatively estimated to range from 0.007 to 0.121 µg/kg bw/d based on the mean intake for children (1-5 years old).

High-Throughput Screening and Quantitative Chemical Ranking for Sodium-Iodide Symporter Inhibitors in ToxCast Phase I Chemical Library

Thyroid uptake of iodide via the sodium-iodide symporter (NIS) is the first step in the biosynthesis of thyroid hormones that are critical for health and development in humans and wildlife. Despite having long been a known target of endocrine disrupting chemicals such as perchlorate, information regarding NIS inhibition activity is still unavailable for the vast majority of environmental chemicals. This study applied a previously validated high-throughput approach to screen for NIS inhibitors in the ToxCast phase I library, representing 293 important environmental chemicals. Here 310 blinded samples were screened in a tiered-approach using an initial single-concentration (100 μM) radioactive-iodide uptake (RAIU) assay, followed by 169 samples further evaluated in multi-concentration (0.001 μM-100 μM) testing in parallel RAIU and cell viability assays. A novel chemical ranking system that incorporates multi-concentration RAIU and cytotoxicity responses was also developed as a standardized method for chemical prioritization in current and future screenings. Representative chemical responses and thyroid effects of high-ranking chemicals are further discussed. This study significantly expands current knowledge of NIS inhibition potential in environmental chemicals and provides critical support to U.S. EPA's Endocrine Disruptor Screening Program (EDSP) initiative to expand coverage of thyroid molecular targets, as well as the development of thyroid adverse outcome pathways (AOPs).

Evaluation of hypothalamus-pituitary-thyroid axis function by chronic perchlorate exposure in male rats

Perchlorate is a widespread endocrine disruptor that was previously correlated with increased serum TSH levels and decreased thyroid hormones production both in animals and humans. Even so, the regulation of gene/protein expression in the hypothalamus, pituitary and thyroid by chronic perchlorate exposure was not completely elucidated. Therefore, this study aimed to investigate the underlying mechanisms involved in the disruption of hypothalamus-pituitary-thyroid axis by chronic perchlorate exposure. Male Wistar rats were treated or not with NaClO₄ in the drinking water (35 mg/Kg/day) for 60 days. Thereafter, hormone/cytokines serum levels were measured through multiplex assays; genes/proteins expression were investigated by qPCR/Western Blotting and thyroid morphology was evaluated through histological analysis. Serum TSH levels were increased and serum T₄ /T₃ levels were decreased in perchlorate-treated animals. This treatment also altered the thyrotropin-releasing hormone mRNA/protein content in the hypothalamus. Additionally, the expression of both subunits of TSH were increased in the pituitary of perchlorate-treated rats, which also presented significant alterations in the thyroid morphology/gene expression. Furthermore, perchlorate exposure reduced liver Dio1 mRNA expression and increased the content of pro-inflammatory cytokines in the thyroid and the serum. In conclusion, our study adds novel findings about the perchlorate-induced disruption of the hypothalamus-pituitary-thyroid axis gene/protein expression in male rats. The data presented herein also suggest that perchlorate induces thyroid and systemic inflammation through the increased production of cytokines. Taken together, our results suggest that perchlorate contamination should be monitored, especially in the individuals most susceptible to the deleterious effects of reduced levels of thyroid hormones.

Effect of thiosulfate on rapid start-up of sulfur-based reduction of high concentrated perchlorate: A study of kinetics, extracellular polymeric substances (EPS) and bacterial community structure

Perchlorate (ClO₄^-) contamination is more and more concerned due to the hazards to humans. Based on the common primary bacterium (Helicobacteraceae) of both thiosulfate-acclimated sludge (T-Acc) and sulfur-acclimated sludge (S-Acc) for perchlorate reduction, the rapid start-up of sulfur-based perchlorate reduction reactor (SBPRR) was hypothesized by inoculating T-Acc. Furthermore, the performance of SBPRR, the SO₄^2- yield, kinetics of ClO₄^- reduction and the extracellular polymeric substances (EPS) of biofilm confirmed the hypothesis. The start-up time of R3 (reactor inoculating T-Acc) was 0.18 and 0.21 times that of R1 (control) and R2 (reactor with the influent containing thiosulfate), respectively. The SO₄^2- yield of R3 was lower than that of R2 and R1 with perchlorate removal rate 166.7mg/(Lh). The kinetic study and EPS demonstrated that inoculating T-Acc was beneficial for the development of biofilm. Consequently, the present study indicated that SBPRR can be rapidly and successfully started-up via inoculation of T-Acc.

Characteristics of electron transport chain and affecting factors for thiosulfate-driven perchlorate reduction

The mechanism for perchlorate reduction was investigated using thiosulfate-driven (T-driven) perchlorate reduction bacteria. The influences of various environmental conditions on perchlorate reduction, including pH, temperature and electron acceptors were examined. The maximum perchlorate removal rate was observed at pH 7.5 and 40 °C. Perchlorate reduction was delayed due to the coexistence of perchlorate-chlorate and perchlorate-nitrate. The mechanism of the T-driven perchlorate reduction electron transport chain (ETC) was also investigated by utilizing different inhibitors. The results were as follows: firstly, the NADH dehydrogenase was not involved in the ETC; secondly, the FAD dehydrogenase and quinone loop participated in the ETC; and thirdly, cytochrome oxidase was the main pathway in the ETC. Meanwhile, microbial consortium structure analysis indicated that Sulfurovum which can oxidize sulfur compounds coupled to the reduction of nitrate or perchlorate was the primary bacterium in the T-driven and sulfur-driven consortium. This study generates a better understanding of the mechanism of T-driven perchlorate reduction.

Predictors of Drinking Water Boiling and Bottled Water Consumption in Rural China: A Hierarchical Modeling Approach

Approximately two billion people drink unsafe water. Boiling is the most commonly used household water treatment (HWT) method globally and in China. HWT can make water safer, but sustained adoption is rare and bottled water consumption is growing. To successfully promote HWT, an understanding of associated socioeconomic factors is critical. We collected survey data and water samples from 450 rural households in Guangxi Province, China. Covariates were grouped into blocks to hierarchically construct modified Poisson models and estimate risk ratios (RR) associated with boiling methods, bottled water, and untreated water. Female-headed households were most likely to boil (RR = 1.36, p < 0.01), and among boilers those using electric kettles rather than pots had higher income proxies (e.g., per capita TV ownership RR = 1.42, p < 0.01). Higher-income households with younger, literate, and male heads were more likely to purchase (frequently contaminated) bottled water, or use electric kettles if they boiled. Our findings show that boiling is not an undifferentiated practice, but one with different methods of varying effectiveness, environmental impact, and adoption across socioeconomic strata. Our results can inform programs to promote safer and more efficient boiling using electric kettles, and suggest that if rural China's economy continues to grow then bottled water use will increase.

Occurrence of perchlorate in groundwater, paired farmland soil, lettuce, and rhizosphere soil from Chengdu, China

A total of 28 groundwater, paired farmland soil, lettuce, and its rhizosphere soil samples were collected from Chengdu, China to detect perchlorate levels and to evaluate the relationships of perchlorate concentrations among these matrices. The perchlorate concentrations in the groundwater, farmland soil, lettuce, and rhizosphere soil samples ranged from below detection limit to 60.2 μg L-1, from below detection limit to 249 μg kg-1 dry weight (dw), from 2.07 to 1010 μg kg-1 wet weight, and from below detection limit to 314 μg kg-1 dw, respectively. Significant correlation was found in the perchlorate levels among the farmland soil, lettuce, and rhizosphere soil, suggesting that they have common pollution sources, or perchlorate might transfer from farmland soil-rhizosphere soil-plant. However, there is no significant correlation between groundwater and the other three matrices, indicating that infiltration from perchlorate contaminated farmland soil was not the predominant source for groundwater pollution in Chengdu. The perchlorate concentrations in the farmland soil and lettuce samples were significantly higher than those in the rhizosphere soil, primarily due to uptake of perchlorate through the rhizosphere micro-environment by lettuce, or accelerated degradation by rhizospheric microorganisms, which contributed more needs further investigation.

Perchlorate Exposure Through Water and Milk in Istanbul

Perchlorate is a chemical pollutant that inhibits iodide uptake and may possibly impair thyroid function. Our previous study found widespread perchlorate exposure in non-pregnant, non-lactating, healthy women residing in Istanbul. The aim of this study is to assess the relative amounts of perchlorate exposure attributable to consumption of municipal water, bottled water and boxed milk available in Istanbul. Only trace levels of perchlorate were found in treated municipal water (58 % detectable, mean = 0.13 µg/L, maximum = 0.75 µg/L) and bottled water (7.4 % detectable, mean = <LOD, maximum = 0.19 µg/L). Conversely, all 30 boxed milk samples contained measurable levels of perchlorate (mean = 4.53 µg/L; maximum = 6.21 µg/L). Median perchlorate exposure attributable to water and milk (0.007 µg/kg/day) is small compared both to the reference dose (0.7 µg/kg/day) and to total perchlorate exposure (0.13 µg/kg/day) in Istanbul. Therefore, additional studies are needed to identify the major sources of perchlorate exposure in Istanbul.

A New Bioinspired Perchlorate Reduction Catalyst with Significantly Enhanced Stability via Rational Tuning of Rhenium Coordination Chemistry and Heterogeneous Reaction Pathway

Rapid reduction of aqueous ClO4(-) to Cl(-) by H2 has been realized by a heterogeneous Re(hoz)2-Pd/C catalyst integrating Re(O)(hoz)2Cl complex (hoz = oxazolinyl-phenolato bidentate ligand) and Pd nanoparticles on carbon support, but ClOx(-) intermediates formed during reactions with concentrated ClO4(-) promote irreversible Re complex decomposition and catalyst deactivation. The original catalyst design mimics the microbial ClO4(-) reductase, which integrates Mo(MGD)2 complex (MGD = molybdopterin guanine dinucleotide) for oxygen atom transfer (OAT). Perchlorate-reducing microorganisms employ a separate enzyme, chlorite dismutase, to prevent accumulation of the destructive ClO2(-) intermediate. The structural intricacy of MGD ligand and the two-enzyme mechanism for microbial ClO4(-) reduction inspired us to improve catalyst stability by rationally tuning Re ligand structure and adding a ClOx(-) scavenger. Two new Re complexes, Re(O)(htz)2Cl and Re(O)(hoz)(htz)Cl (htz = thiazolinyl-phenolato bidentate ligand), significantly mitigate Re complex decomposition by slightly lowering the OAT activity when immobilized in Pd/C. Further stability enhancement is then obtained by switching the nanoparticles from Pd to Rh, which exhibits high reactivity with ClOx(-) intermediates and thus prevents their deactivating reaction with the Re complex. Compared to Re(hoz)2-Pd/C, the new Re(hoz)(htz)-Rh/C catalyst exhibits similar ClO4(-) reduction activity but superior stability, evidenced by a decrease of Re leaching from 37% to 0.25% and stability of surface Re speciation following the treatment of a concentrated "challenge" solution containing 1000 ppm of ClO4(-). This work demonstrates the pivotal roles of coordination chemistry control and tuning of individual catalyst components for achieving both high activity and stability in environmental catalyst applications.

Perchlorate as an emerging contaminant in soil, water and food

Perchlorate ( [Formula: see text] ) is a strong oxidizer and has gained significant attention due to its reactivity, occurrence, and persistence in surface water, groundwater, soil and food. Stable isotope techniques (i.e., ((18)O/(16)O and (17)O/(16)O) and (37)Cl/(35)Cl) facilitate the differentiation of naturally occurring perchlorate from anthropogenic perchlorate. At high enough concentrations, perchlorate can inhibit proper function of the thyroid gland. Dietary reference dose (RfD) for perchlorate exposure from both food and water is set at 0.7 μg kg(-1) body weight/day which translates to a drinking water level of 24.5 μg L(-1). Chromatographic techniques (i.e., ion chromatography and liquid chromatography mass spectrometry) can be successfully used to detect trace level of perchlorate in environmental samples. Perchlorate can be effectively removed by wide variety of remediation techniques such as bio-reduction, chemical reduction, adsorption, membrane filtration, ion exchange and electro-reduction. Bio-reduction is appropriate for large scale treatment plants whereas ion exchange is suitable for removing trace level of perchlorate in aqueous medium. The environmental occurrence of perchlorate, toxicity, analytical techniques, removal technologies are presented.

Effects of perchlorate bioaccumulation on Spodoptera litura growth and sex ratio

Perchlorate (ClO4 (-)) pollution is widespread in the natural environment, but the effects of ClO4 (-) on the terrestrial insects are rarely studied. Here, when phytophagous insect Spodoptera litura larvae were fed on the diets with different ClO4 (-) concentrations, changes in their life-history traits were recorded; ClO4 (-) accumulations in feces and insect body were detected. The results demonstrated that ClO4 (-) bioaccumulation in insect at the different developmental stages was ranked in the order: adults > pupae > the 4th > 5th > 6th instar larvae. Besides, ClO4 (-) accumulations in the feces were ranked in the order: the 6th > 5th > 4th instar larvae. The ClO4 (-) accumulations in female pupae and adults were significantly higher than that in males. ClO4 (-) bioaccumulation in insect prolonged larval development time and caused a skewed sex ratio (the percentage of males at metamorphosis significantly decreased) under 100 to 200 mg ClO4 (-)/kg treatment. Therefore, ClO4 (-) accumulations in S. litura body presented developmental stage-, sex-specific pattern, and the sex-specific ClO4 (-) accumulations resulted in difference of sex ratio. These effects were observed at concentrations reported in natural environments contaminated with ClO4 (-), suggesting that this contaminant may pose a threat to the normal development and growth of this insect species.

Mechanism and Mitigation of the Decomposition of an Oxorhenium Complex-Based Heterogeneous Catalyst for Perchlorate Reduction in Water

A biomimetic heterogeneous catalyst combining palladium nanoparticles and an organic ligand-coordinated oxorhenium complex on activated carbon, Re(hoz)2-Pd/C, was previously developed and shown to reduce aqueous perchlorate (ClO4-) with H2 at a rate ∼100 times faster than the first generation ReOx-Pd/C catalyst prepared from perrhenate (ReO4-). However, the immobilized Re(hoz)2 complex was shown to partially decompose and leach into water as ReO4-, leading to an irreversible loss of catalytic activity. In this work, the stability of the immobilized Re(hoz)2 complex is shown to depend on kinetic competition between three processes: (1) ReV(hoz)2 oxidation by ClO4- and its reduction intermediates ClOx-, (2) ReVII(hoz)2 reduction by Pd-activated hydrogen, and (3) hydrolytic ReVII(hoz)2 decomposition. When ReV(hoz)2 oxidation is faster than ReVII(hoz)2 reduction, the ReVII(hoz)2 concentration builds up and leads to hydrolytic decomposition to ReO4- and free hoz ligand. Rapid ReV(hoz)2 oxidation is mainly promoted by highly reactive ClOx- formed from the reduction of ClO4-. To mitigate Re(hoz)2 decomposition and preserve catalytic activity, ruthenium (Ru) and rhodium (Rh) were evaluated as alternative H2 activators to Pd. Rh showed superior activity for reducing the ClO3- intermediate to Cl-, thereby preventing ClOx- buildup and lowering Re complex decomposition in the Re(hoz)2-Rh/C catalyst. In contrast, Ru showed the lowest ClO3- reduction activity and resulted in the most Re(hoz)2 decomposition among the Re(hoz)2-M/C catalysts. This work highlights the importance of using mechanistic insights from kinetic and spectroscopic tests to rationally design water treatment catalysts for enhanced performance and stability.

Perchlorate in dust fall and indoor dust in Malta: An effect of fireworks

We report on the presence of perchlorate in the settleable dust of Malta, a small central Mediterranean island. Both dust fall collected directly as it precipitated from atmosphere over a period of one month and deposited indoor dust from domestic residences were studied. Perchlorate was determined by ion chromatography of water extracts of the collected dusts. Dust fall was collected from 43 towns during 2011 to 2013 and indoor dust was sampled from homes in the same localities. Perchlorate was detected in 108 of 153 samples of dust fall (71%) and in 28 of 37 indoor dust samples (76%). Detectable perchlorate in dust fall ranged from 0.52μgg(-1) to 561μgg(-1) with a median value of 6.2μgg(-1); in indoor dust, levels were from 0.79μgg(-1) to 53μgg(-1) with a median value of 7.8μgg(-1), the highest recorded anywhere to date. Statistical analysis suggested that there was no significant difference in perchlorate content of indoor dust and dust fall. Perchlorate levels in dust fall escalate during the summer in response to numerous religious feasts celebrated with fireworks and perchlorate persists at low μgg(-1) concentrations for several months beyond the summer festive period. In Malta, perchlorate derives exclusively from KClO4, imported for fireworks manufacture. Its residue in dust presents an exposure risk to the population, especially via ingestion by hand to mouth transfer. Our results suggest that wherever intensive burning of fireworks takes place, the environmental impact may be much longer lived than realised, mainly due to re-suspension and deposition of contaminated settled dust in the urban environment.

Perchlorate in indoor dust and human urine in China: contribution of indoor dust to total daily intake

Perchlorate is used in fireworks and China is the largest fireworks producer and consumer in the world. Information regarding human exposure to perchlorate is scarce in China, and exposure via indoor dust ingestion (EDI indoor dust) has rarely been evaluated. In this study, perchlorate was found in indoor dust (detection rate: 100%, median: 47.4 μg/g), human urine (99%, 26.2 ng/mL), drinking water (100%, 3.99 ng/mL), and dairy milk (100%, 12.3 ng/mL) collected from cities that have fireworks manufacturing areas (Yueyang and Nanchang) and in cities that do not have fireworks manufacturing industries (Tianjin, Shijiazhuang, Yuxi and Guilin) in China. In comparison with perchlorate levels reported for other countries, perchlorate levels in urine samples from fireworks sites and nonfireworks sites in China were higher. Median indoor dust perchlorate concentrations were positively correlated (r = 0.964, p < 0.001) with outdoor dust perchlorate levels reported previously. The total daily intake (EDI total) of perchlorate, estimated based on urinary levels, ranged from 0.090 to 27.72 μg/kg body weight (bw)/day for all studied participants; the percentage of donors who had EDI total exceeding the reference dose (RfD) recommended by the United States Environmental Protection Agency (US EPA) was 79%, 48%, and 25% for toddlers (median: 1.829 μg/kg bw/day), adults (0.669 μg/kg bw/day), and children (median: 0.373 μg/kg bw/day), respectively. Toddlers (0.258 μg/kg bw/day) had the highest median EDI indoor dust, which was 2 to 5 times greater than the EDI indoor dust calculated for other age groups (the range of median values: 0.044 to 0.127 μg/kg bw/day). Contribution of indoor dust to EDItotal was 26%, 28%, and 7% for toddlers, children, and adults, respectively. Indoor dust contributed higher percentage to EDI total than that by dairy milk (0.5-5%).

Occurrence of perchlorate in indoor dust from the United States and eleven other countries: implications for human exposure

Perchlorate is a widespread environmental contaminant and potent thyroid hormone disrupting compound. Despite this, very little is known with regard to the occurrence of this compound in indoor dust and the exposure of humans to perchlorate through dust ingestion. In this study, 366 indoor dust samples were collected from 12 countries, the USA, Colombia, Greece, Romania, Japan, Korea, Pakistan, Kuwait, Saudi Arabia, India, Vietnam, and China, during 2010-2014. Dust samples were extracted by 1% (v/v) methylamine in water. Analyte separation was achieved by an ion exchange (AS-21) column and analysis was performed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The overall concentrations of perchlorate in dust were in the range of 0.02-104μg/g (geometric mean: 0.41μg/g). The indoor dust samples from China contained the highest concentrations (geometric mean: 5.38μg/g). No remarkable differences in perchlorate concentrations in dust were found among various microenvironments (i.e., car, home, office, and laboratory). The estimated median daily intake (EDI) of perchlorate for toddlers through dust ingestion in the USA, Colombia, Greece, Romania, Japan, Korea, Pakistan, Kuwait, Saudi Arabia, India, Vietnam, and China was 1.89, 0.37, 1.71, 0.74, 4.90, 7.20, 0.60, 0.80, 1.55, 0.70, 2.15, and 21.3ng/kgbodyweight (bw)/day, respectively. Although high concentrations of perchlorate were measured in some dust samples, the contribution of dust to total perchlorate intake was <5% of the total perchlorate intake in humans. This is the first multinational survey on the occurrence of perchlorate in indoor dust.

Silver nanoplate-decorated copper wire for the on-site microextraction and detection of perchlorate using a portable Raman spectrometer

Silver nanoplates were decorated on a copper wire for the on-site microextraction and detection of perchlorate using a portable Raman spectrometer.

Surveillance of perchlorate in ground water, surface water and bottled water in Kerala, India

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.

Environmental impacts of perchlorate with special reference to fireworks--a review

Perchlorate is an inorganic anion that is used in solid rocket propellants, fireworks, munitions, signal flares, etc. The use of fireworks is identified as one of the main contributors in the increasing environmental perchlorate contamination. Although fireworks are displayed for entertainment, its environmental costs are dire. Perchlorates are also emerging as potent thyroid disruptors, and they have an impact on the ecology too. Many studies have shown that perchlorate contaminates the groundwater and the surface water, especially in the vicinity of fireworks manufacturing sites and fireworks display sites. The health and ecological impacts of perchlorate released in fireworks are yet to be fully assessed. This paper reviews fireworks as a source of perchlorate contamination and its expected adverse impacts.

The association between perchlorate and thiocyanate exposure and thyroid function in first-trimester pregnant Thai women

CONTEXT

Thyroid hormone is critical for fetal neurodevelopment. Perchlorate and thiocyanate decrease thyroidal iodine uptake by competitively inhibiting the sodium/iodide symporter. It is clear that perchlorate and thiocyanate anions can influence thyroid function. However, as pollutants in the environment, their impact is conflicting.

OBJECTIVE

The objective was to determine the effects of environmental perchlorate and/or thiocyanate exposure on thyroid function in first-trimester pregnant women.

DESIGN AND PATIENTS

A cross-sectional study was conducted in 200 pregnant Thai women with a gestational age of 14 weeks or less.

MEASURES

Urinary iodide, perchlorate, thiocyanate, and serum thyroid function tests were measured.

RESULTS

The women were aged 28.6 ± 6.1 years and the mean gestational age was 9.6 ± 2.7 weeks. Median urinary iodide, perchlorate, and thiocyanate concentrations were 153.5 μg/L, 1.9 μg/L, and 510.5 μg/L, respectively. Using Spearman's rank correlation analyses, there were positive correlations between serum TSH and urine perchlorate to creatinine (r = 0.20, P = .005) and TSH and thiocyanate to creatinine ratios (r = 0.22, P = .001). There were negative correlations between free T4 and the perchlorate to creatinine ratio (r = -0.18, P = .01) and free T4 and the thiocyanate to creatinine ratio (r = -0.19, P = .008). In multivariate analyses adjusting for log thiocyanate to creatinine ratio, log iodide to creatinine ratio, and gestational age, log perchlorate to creatinine ratio was positively associated with log TSH (P = .002) and inversely associated with log free T4 (P = .002). Log thiocyanate to creatinine ratio was a significant positive predictor of log TSH (P = .02) in women with a urine iodide level of less than 100 μg/L.

CONCLUSIONS

Low-level environmental exposure to perchlorate and thiocyanate is common in Thailand. Low-level exposure to perchlorate is positively associated with TSH and negatively associated with free T4 in first-trimester pregnant women using multivariate analyses. In multivariate analyses, thiocyanate exposure is also positively associated with TSH in a subgroup of pregnant women with low iodine excretion.

Urinary perchlorate exposure and risk in women of reproductive age in a fireworks production area of China

Perchlorate is used widely in fireworks, and, if ingested, it has the potential to disrupt thyroid function. The concentrations of perchlorate in water and soil samples and in urine samples of women of reproductive age from Liuyang, the largest fireworks production area in China, were investigated. The results showed that the average perchlorate concentrations in groundwater, surface water, farmland soil, and urine samples of women from the fireworks production area were significantly greater than those from the control area. The health risk of perchlorate ingested through drinking water was assessed based on the mode recommended by the United States Environmental Protection Agency. The values of hazard quotient of river water and groundwater in the fireworks production area were much greater than the safe level (=1), which indicates that adverse health effects may result from perchlorate when these sources of water are used as drinking water. These results indicated that the environment of the fireworks production area has been polluted by perchlorate and that residents were and are facing greater exposure doses of perchlorate. Fireworks production enterprises may be a major source of perchlorate contamination.

Iodine status in Turkish populations and exposure to iodide uptake inhibitors

Perchlorate, nitrate, and thiocyanate are competitive inhibitors of the sodium iodide symporter of the thyroid membrane. These inhibitors can decrease iodine uptake by the symporter into the thyroid gland and may disrupt thyroid function. This study assesses iodine status and exposure to iodide uptake inhibitors of non-pregnant and non-lactating adult women living in three different cities in Turkey (Istanbul, Isparta and Kayseri). We measured iodine and iodide uptake inhibitors in 24-hr urines collected from study participants (N = 255). All three study populations were mildly iodine deficient, with median urinary iodine (UI) levels of 77.5 µg/L in Istanbul, 58.8 µg/L in Isparta, and 69.8 µg/L in Kayseri. Perchlorate doses were higher in the study population (median 0.13 µg/kg/day), compared with a reference population (median 0.059 µg/kg/day), but lower than the U.S. EPA reference dose (0.7 µg/kg/day). Urinary thiocyanate levels increased with increasing exposure to tobacco smoke, with non-smokers (268 µg/L) significantly lower than light smokers (1110 µg/L), who were significantly lower than heavy smokers (2410 µg/L). This pilot study provides novel data indicating that study participants were moderately iodine deficient and had higher intakes of the iodide uptake inhibitor perchlorate compared with a reference population. Further investigation is needed to characterize the thyroid impact resulting from iodine deficiency coupled with exposure to iodide uptake inhibitors such as perchlorate, thiocyanate and nitrate.