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PubMed1999

Determination of trace level perchlorate in drinking water and ground water by ion chromatography.

Ammonium perchlorate, a key ingredient in solid rocket propellants, has recently been found in ground and surface waters in the USA in a number of states, including California, Nevada, Utah, and West Virginia. Perchlorate poses a health risk and preliminary data from the US Environmental Protection Agency reports that exposure to less than 4-18 micrograms/l provides adequate human health protection. An ion chromatographic method was developed for the determination of low microgram/l levels of perchlorate in drinking and ground waters based on a Dionex IonPac AS11 column, a 100 mM hydroxide eluent, large loop (1000 microliters) injection, and suppressed conductivity detection. The method is free of interferences from common anions, linear in the range of 2.5-100 micrograms/l, and quantitative recoveries were obtained for low microgram/l levels of perchlorate in spiked drinking and ground water samples. The method detection limit of 0.3 microgram/l permits quantification of perchlorate below the levels which ensure adequate health protection. A new polarizable anion analysis column, the IonPac AS16, and its potential applicability for this analysis is also discussed.

Anions↗
PubMed2003

Determination of trace perchlorate in high-salinity water samples by ion chromatography with on-line preconcentration and preelution.

A simple, automated system for the determination of trace perchlorate by ion chromatography (IC) with an online preconcentration technique is reported. The sample is preconcentrated, and less strongly held ions preeluted before the analyte is transferred to the principal separation system. This approach provides low limits of detection (LOD) and is particularly robust toward the effect of high concentrations of common anions, such as those present in groundwater samples. It compares favorably with currently promulgated EPA method 314.0. The LOD (S/N = 3) is 0.77 microg/L for a 2-mL reagent water sample and decreases more-or-less proportionately with increasing sample volume, at least up to 20 mL. Even with a sample of conductivity 14.7 mS/cm (approximately that of 0.1 M Na2SO4), the recovery of added perchlorate at the 25.0 microg/L level was still 92%. The concentration of added perchlorate in the range of 1-400 microg/L was linearly correlated to the peak area, with an r2 value of 0.9997. The recovery of perchlorate from artificial samples with different conductivity by the present method compares favorably with those from the currently recommended EPA Method. The ability of this approach to remove matrix interferences suggests that it would be also promising for perchlorate analysis in other challenging samples.

Fresh Water↗
PubMed2006

Perchlorate in the United States. Analysis of relative source contributions to the food chain.

Perchlorate has been considered by some a potential threat to human health, especially to developing infants and children because it may inhibit iodide uptake by the sodium iodide symporter (NIS) of the thyroid. In the United States, during the last several decades, environmental perchlorate has had three recognized sources stemming from (a) its use as an oxidizer (including in rocket propellants), (b) its presence in Chilean nitrate fertilizer (CNF), and (c) natural production. An analysis of the relative source strengths and how they may influence entry into the food chain has not been conducted. Averaged over the last --60 years, we estimate that the source strengths have been (a) 10.6, (b) 0.75, and (c) 0.13-0.64 Gg/y for the United States as a whole. Of this, while (b) and (c) represent actual dispersed amounts, the figure in (a) is the amount of perchlorate produced and only a fraction (f) of it has been dispersed and often in a more localized fashion. In addition, dispersal of (b) has taken place only over agricultural land. Considering that the total land area in the United States is 5.5 x the arable land area, in terms of incorporation into the food chain,the figure cited in (b) has a proportionately greater impact. Most estimates of fwill thus suggest that over the considered period, the contribution of CNF to incorporation of perchlorate in the food chain has likely been comparable to oxidizer perchlorate, with natural production being a lesser source. Fireworks presently constitute a potentially important source of increasing importance but a quantitative impact cannotyet be assessed.

Biological Availability↗
PubMed2002

Performance of poly(vinyl alcohol) gel columns on the ion chromatographic determination of perchlorate in fertilizers.

Interest in possible sources of perchlorate (ClO4) that could lead to environmental release has been heightened since the Environmental Protection Agency placed this anion on its Contaminant Candidate List for drinking water. Although recent investigations have suggested that fertilizers are minor contributors to environmental perchlorate contamination overall, there is still interest in screening commercial products for possible contamination and quantitating perchlorate when it is found. Ion chromatography (IC) has been used for this application owing to its speed, low detection limits, widespread availability, and moderate ruggedness relative to other techniques. However, fertilizer matrixes complicate the IC analysis relative to potable water matrixes. In this study, the performance of poly(vinyl alcohol) gel resin IC columns (100 mm and 150 mm) was evaluated for fertilizer matrixes using method EPA/600/R-01/026. The NaOH eluent included an organic salt, sodium 4-cyanophenoxide. Detection was by suppressed conductivity. A set of 55 different field samples representing 48 products and previously used by the EPA to assess occurrence of perchlorate in fertilizers (EPA/600/R-01/049) was reanalyzed on the 150 mm column. The 100 mm column was used to further investigate the positive hits. Both columns gave satisfactory performance in fertilizer matrixes, with spike recoveries (+/- 15%), assured reporting levels (0.5-225 microg g(-1) except for one at 1,000 microg g(-1)), accuracy (relative error < 30% always and most < 15%), and precision [injection-to-injection reproducibility < 3% relative standard deviation (RSD)] comparable to those reported in other studies. Performance did not vary substantially between column lengths. Lastly, the results of this investigation provided further evidence in support of the conclusions that had been reached previously by the EPA on the occurrence of perchlorate in fertilizers.

Chromatography, Ion Exchange↗
PubMed2006

Development of an extraction method for perchlorate in soils.

Perchlorate originates as a contaminant in the environment from its use in solid rocket fuels and munitions. The current US EPA methods for perchlorate determination via ion chromatography using conductivity detection do not include recommendations for the extraction of perchlorate from soil. This study evaluated and identified appropriate conditions for the extraction of perchlorate from clay loam, loamy sand, and sandy soils. Based on the results of this evaluation, soils should be extracted in a dry, ground (mortar and pestle) state with Milli-Q water in a 1 ratio 1 soil ratio water ratio and diluted no more than 5-fold before analysis. When sandy soils were extracted in this manner, the calculated method detection limit was 3.5 microg kg(-1). The findings of this study have aided in the establishment of a standardized extraction method for perchlorate in soil.

Chromatography, Ion Exchange↗
PubMedDate not supplied

Two-generation reproduction study of ammonium perchlorate in drinking water in rats evaluates thyroid toxicity.

Perchlorate is an inorganic ion that has recently been detected in drinking water supplies throughout the country, but little is known about its effects on reproductive function. This two-generation reproductive study examines the effects of ammonium perchlorate on the male and female reproductive systems in rats, and on the growth and development of offspring. Adult Sprague-Dawley rats (30/sex/group) were given continuous access to ammonium perchlorate in their drinking water at doses of 0, 0.3, 3.0, and 30.0 mg/kg-day. F1 generation rats were given the same ammonium perchlorate doses as their respective P1 generation sires and dams beginning at weaning and continuing through the day of sacrifice. Standard reproductive parameters were evaluated; blood was collected for determination of serum thyroid-stimulating hormone (TSH), triiodothyronine (T3), and thyroxine (T4) levels. Histopathological examination was conducted on major tissues, including the thyroid. No significant changes in developmental parameters were observed. In the F1 generation adult rats, relative thyroid weights were significantly increased in all dose groups for female rats and in the 3.0 and 30.0 mg/kg-day dose groups for male rats. Histopathologic changes in the thyroid consisted of hypertrophy and hyperplasia that increased in incidence and severity in a dose-related manner. Dose-related, statistically significant changes in TSH and T4 or T3 occurred at doses higher than those that resulted in changes in thyroid weight and thyroid histopathology, 30 mg/kg-day. Thus, perchlorate is not a reproductive toxicant in rats when administered in the drinking water at doses up to 30 mg/kg-day, but it can affect the thyroid at doses > or =3 mg/kg-day. Based on these findings, 0.3 mg/kg-day is identified to be the no-observable-adverse-effect level (NOAEL) for this study.

Animals↗
PubMed2006

Estimates of exposures to perchlorate from consumption of human milk, dairy milk, and water, and comparison to current reference dose.

To develop an enforceable drinking water standard from a health-based reference dose, sources of exposure and relevant exposure factors across the U.S. population must be considered. Human exposures, expressed as an estimated daily exposure, can be used to evaluate the health protectiveness of a range of potential regulatory values, thus providing a scientific foundation on which decisions can be based. Recent evidence points to detectable levels of perchlorate in milk and other foods. The purpose of this article is to estimate human exposure to perchlorate from ingestion of drinking water, human milk, and dairy milk. Drinking-water exposure was based on a range of possible regulatory values, derived from the recently established reference dose. Exposure to perchlorate from the consumption of milk was based on exploratory Food and Drug Administration dairy milk data, and on additional published perchlorate concentrations in dairy and human milk samples. This effort is exploratory in nature due to the limited data available at this time. However, it is anticipated that these exposure estimates and comparison with the current reference dose will stimulate dialogue and research that will advance the risk assessment for perchlorate.

Animals↗
PubMed2005

Perchlorate and nitrate remediation efficiency and microbial diversity in a containerized wetland bioreactor.

We have developed a method to remove perchlorate (14-27 microg/L) and nitrate (48 mg/L) from contaminated groundwater using a wetland bioreactor. The bioreactor has operated continuously in a remote field location for more than 2 yr with a stable ecosystem of indigenous organisms. This study assesses the bioreactorfor long-term perchlorate and nitrate remediation by evaluating influent and effluent groundwater for oxidation-reduction conditions and nitrate and perchlorate concentrations. Total community DNA was extracted and purified from 10-g sediment samples retrieved from vertical coring of the bioreactor during winter. Analysis by denaturing gradient gel electrophoresis of short, 16S rDNA, polymerase-chainreaction products was used to identify dominant microorganisms. Bacteria genera identified were closely affiliated with bacteria widely distributed in soils, mud layers, and fresh water. Of the 17 dominant bands sequenced, most were gram negative and capable of aerobic or anaerobic respiration with nitrate as the terminal electron acceptor (Pseudomonas, Acinetobacter, Halomonas, and Nitrospira). Several identified genera (Rhizobium, Acinetobactor, and Xanthomonas) are capable of fixing atmospheric nitrogen into a combined form (ammonia) usable by host plants. Isolates were identified from the Proteobacteria class, known for the ability to reduce perchlorate. Initial bacterial assessments of sediments confirm the prevalence of facultative anaerobic bacteria capable of reducing perchlorate and nitrate in situ.

Bacteria↗
PubMed2003

PBPK predictions of perchlorate distribution and its effect on thyroid uptake of radioiodide in the male rat.

Due to perchlorate's (ClO4-) ability to competitively inhibit thyroid iodide (I-) uptake through the sodium-iodide symporter (NIS), potential human health risks exist from chronic exposure via drinking water. Such risks may include hypothyroidism, goiter, and mental retardation (if exposure occurs during critical periods in neurodevelopment). To aid in predicting perchlorate's effect on normal I- kinetics, we developed a physiologically-based pharmacokinetic (PBPK) model for the adult male rat. The model structure describes simultaneous kinetics for both anions together with their interaction at the NIS, in particular, the inhibition of I- uptake by ClO4-. Subcompartments and Michaelis-Menten (M-M) kinetics were used to describe active uptake of both anions in the thyroid, stomach, and skin. Separate compartments for kidney, liver, plasma, and fat were described by passive diffusion. The model successfully predicts both 36ClO4- and 125I- kinetics after iv doses of 3.3 mg/kg and 33 mg/kg, respectively, as well as inhibition of thyroid 125I- uptake by ClO4- after iv doses of ClO4- (0.01 to 3.0 mg/kg). The model also predicts serum and thyroid ClO4- concentrations from 14-day drinking water exposures (0.01 to 30.0 mg ClO4-/kg/day) and compensation of perchlorate-induced inhibition of radioiodide uptake due to upregulation of the thyroid. The model can be used to extrapolate dose metrics and correlate observed effects in perchlorate toxicity studies to other species and life stages, such as rat gestation (Clewell et al., 2003). Because the model successfully predicts perchlorate's interaction with iodide, it provides a sound basis for future incorporation of the complex hypothalamic-pituitary-thyroid feedback system.

Animals↗
PubMed2006

The colloidal thyroxine (T4) ring as a novel biomarker of perchlorate exposure in the African clawed frog Xenopus laevis.

The purpose of this study was to determine if changes in colloidal thyroxine (T(4)) immunoreactivity can be used as a biomarker of perchlorate exposure in amphibian thyroid tissue. Larval African clawed frogs (Xenopus laevis) were exposed to 0, 1, 8, 93, and 1131 microg perchlorate/l for 38 and 69 days to cover the normal period of larval development and metamorphosis. The results of this study confirmed the presence of an immunoreactive colloidal T(4) ring in thyroid follicles of X. laevis and demonstrated that the intensity of this ring is reduced in a concentration-dependent manner by perchlorate exposure. The smallest effective concentration of perchlorate capable of significantly reducing colloidal T(4) ring intensity was 8 microg perchlorate/l. The intensity of the immunoreactive colloidal T(4) ring is a more sensitive biomarker of perchlorate exposure than changes in hind limb length, forelimb emergence, tail resorption, thyrocyte hypertrophy, or colloid depletion. We conclude that the colloidal T(4) ring can be used as a sensitive biomarker of perchlorate-induced thyroid disruption in amphibians.

Animals↗
PubMed1998

Evaluation of a population with occupational exposure to airborne ammonium perchlorate for possible acute or chronic effects on thyroid function.

Employees at an ammonium perchlorate production facility in Nevada and a larger control population from the same chemical complex without direct AP exposure were monitored extensively for airborne perchlorate exposure. Single-shift and working-lifetime cumulative dose estimates were made using standard breathing-rate estimates and assuming rapid absorption, based upon solubility. Calculated single-shift doses ranged from 0.2 to 436 micrograms/kg, with an average of 36 micrograms/kg. Working-lifetime cumulative doses in the higher exposure group ranged from 8,000 to 88,000 micrograms/kg, with an average of 38,000 micrograms/kg. Thyroid profiles, including free thyroxine index and thyroid-stimulating hormone level, were obtained both before shift and after shift to assess thyroid-axis perturbation due to single working-shift perchlorate exposure. Thyroid-function data were also analyzed with respect to estimates of cumulative exposure to assess any measurable chronic effects on thyroid gland function. Additionally, standard clinical blood test parameters of liver, kidney, and bone marrow function were evaluated to assess any measurable chronic effects of perchlorate exposure on those organs. Multiple regression was used to assess the effects of exposure variables and demographic variables on organ function parameters. No perchlorate-attributable effects on thyroid, bone marrow, kidney, or liver function were detected.

Acute Disease↗
PubMed2000

Neonatal thyroxine level and perchlorate in drinking water.

Environmental contamination of drinking water has been observed for perchlorate, a chemical able to affect thyroid function. This study examines whether that exposure affected the thyroid function of newborns. Neonatal blood thyroxine (T4) levels for days 1 to 4 of life were compared for newborns from the city of Las Vegas, Nevada, which has perchlorate in its drinking water, and those from the city of Reno, Nevada, which does not (detection limit, 4 micrograms/L [ppb]). This study is based on blood T4 analyses from more than 23,000 newborns in these two cities during the period April 1998 through June 1999. No difference was found in the mean blood T4 levels of the newborns from these two cities. Drinking water perchlorate levels measured monthly for Las Vegas ranged during this study period from non-detectable for 8 months to levels of 9 to 15 ppb for 7 months. Temporal differences in mean T4 level were noted in both cities but were unrelated to the perchlorate exposure. This study was sufficiently sensitive to detect the effects of gender, birth weight, and the day of life on which the blood sample was taken on the neonatal T4 level, but it detected no effect from environmental exposures to perchlorate that ranged up to 15 micrograms/L (ppb).

Chi-Square Distribution↗
PubMed2000

Does perchlorate in drinking water affect thyroid function in newborns or school-age children?

Perchlorate is known to suppress thyroid function by inhibiting uptake of iodide by the human thyroid at doses of 200 mg/day or greater. A study was conducted to investigate the potential effects of perchlorate in drinking water on thyroid function in newborns and school-age children. A total of 162 school-age children and 9784 newborns were studied in three proximate cities in northern Chile that have different concentrations of perchlorate in drinking water: Taltal (100 to 120 micrograms/L), Chañaral (5 to 7 micrograms/L), and Antofagasta (non-detectable: < 4 micrograms/L). Among schoolchildren, no difference was found in thyroid-stimulating hormone levels or goiter prevalence among lifelong residents of Taltal or Chañaral compared with those of Antofagasta, after adjusting for age, sex, and urinary iodine. No presumptive cases of congenital hypothyroidism were detected in Taltal or Chañaral; seven cases were detected in Antofagasta. Neonatal thyroid-stimulating hormone levels were significantly lower in Taltal compared with Antofagasta; this is opposite to the known pharmacological effect of perchlorate, and the magnitude of difference did not seem to be clinically significant. These findings do not support the hypothesis that perchlorate in drinking water at concentrations as high as 100 to 120 micrograms/L suppresses thyroid function in newborns or school-age children.

Age Distribution↗
PubMed2001

Prevalence of thyroid diseases in Nevada counties with respect to perchlorate in drinking water.

Perchlorate is well-known to inhibit the uptake of iodine by the thyroid and has been shown to do so at doses in the milligrams-per-day range and higher. Perchlorate has been found in the water supply of Clark County (Las Vegas), Nevada, at 4 to 24 micrograms/L (parts per billion) and may provide exposure dosages in the tens of micrograms per day. An analysis of the Medicaid database from Nevada was undertaken to determine whether an increase in the prevalence of any thyroid disease was associated with that level of perchlorate content. The prevalence of persons being seen for thyroid disease or for specific thyroid diseases (goiter, nodule, thyrotoxicosis, congenital hypothyroidism, acquired hypothyroidism, thyroiditis, and other thyroid disorders) and for thyroid cancer among the Medicaid-eligible population of each county was calculated for the 2-year period 1997 to 1998. The prevalences in Clark County were compared with those in Washoe County (i.e., Reno), the second most populous county in the state, and with those for the rest of the state. There was no evidence of an increased rate of thyroid disease (or of any specific thyroid disease) associated with perchlorate exposure. Generally, the prevalences in the metropolitan parts of the state were lower than for the rest of the state, particularly for acquired hypothyroidism. This analysis found no evidence that perchlorate-containing drinking water at the given level increased the prevalence of acquired hypothyroidism or of any other thyroid condition.

Humans↗
PubMed1980

Perchlorate binding to cytochrome c: a magnetic and optical study.

1. The effects of perchlorate on cytochrome c have been investigated by 1H and 35Cl NMR, electron paramagnetic resonance and optical spectroscopy. 2. The pK values for the formation and disappearance of the major alkaline conformation were found to be displaced from 9.3 to 8.3 and from 10.4 to 10.9, respectively. The displacement was dependent on the ClO4(-) concentration below 0.1 M. 3. Competition experiments between perchlorate and chloride show that ClO4(-) binds both to the neutral and alkaline forms but with a higher affinity for the latter. The appearance of a new binding site in the alkaline form accounts for the markedly enhanced relaxation rate of 35ClO4(-) in this pH range. Complex formation between cyanide and the alkaline species results in the loss of this binding site, which probably is located close to or within the heme crevice. 4. The neutral form of ferricytochrome c also binds perchlorate strongly as evidence by the unique appearance of a high-spin signal dependent on pH and perchlorate concentration. This signal disappears with the same pK value as the neutral form. The effects of perchlorate on cytochrome c are due to specific binding of this ion.

Animals↗
PubMed1998

Purification, characterization and differentiation-dependent expression of a perchloric acid soluble protein from rat kidney.

We have recently reported the presence of a novel perchloric acid soluble protein in rat liver (PSP1) that inhibits cell-free protein synthesis in a rabbit reticulocyte system. While studying the perchloric acid soluble proteins from different tissues of rats, we found that the kidney protein cross-reacted with antibody against the PSP1. In this investigation, we have purified a perchloric acid soluble protein from the rat kidney and studied its characterization and expression. The protein extracted from the postmitochondrial supernatant fraction with 5% perchloric acid was purified by ammonium sulfate fractionation and CM-Sephadex chromatography. By immunoscreening with the rabbit antisera against the PSP1, we detected a cDNA that contained an open reading frame of 411 bp, encoding a 137 amino-acid protein with a molecular mass of 14,149 daltons. The deduced amino acid sequence was completely identical with that of PSP1 from rat liver. The perchloric acid soluble protein from rat kidney (K-PSP1) also inhibited cell-free protein synthesis in the rabbit reticulocyte lysate system in a different manner than RNase A. Immunohistochemistry showed that the expression of K-PSP1 increased from fetal 17th day to postnatal 4th week, and it remained almost the same until the 7th week of postnatal age. Furthermore, the expression of K-PSP1 in the kidney of the nephrotic rat model was shown to be differentiation dependent. On the other hand, the expression of K-PSP1 in renal tumor cells was downregulated as compared with intact tissue. These results suggest that the expression of K-PSP1 is regulated in a differentiation-dependent manner in the kidney.

Amino Acid Sequence↗
PubMed2001

The use of physiologically based models to integrate diverse data sets and reduce uncertainty in the prediction of perchlorate and iodide kinetics across life stages and species.

The effects of perchlorate on the incorporation of iodide into thyroid hormones have been studied for more than 40 years in many species and under varying exposure conditions. Nevertheless, the database for this drinking water contaminant is still incomplete, particularly with regard to human developmental risk. A method for integrating the available data and forming meaningful conclusions for risk assessment is needed. To this end, an initial suite of physiologically based pharmacokinetic (PBPK) models has been developed, which incorporates physiological data for the relevant species and life stages and kinetic data for perchlorate and iodide, as well as the interaction between the two anions. The validated models successfully describe perchlorate-induced inhibition of thyroid iodide uptake and perchlorate and iodide kinetics in the male, pregnant, lactating, fetal, and neonatal rats and the adult humans. The relationships of model-predicted internal dose metrics and kinetic parameters allow a direct comparison of internal dose metrics across life stages in rats and humans. By incorporating all the available data, these models provide a framework for species and life stage extrapolation where the lack of specific data sets would otherwise limit predictive capability. This paper demonstrates two approaches for calculating life stage-specific equivalent doses in a risk assessment for perchlorate: the direct combination of validated model predictions, and the development of preliminary PBPK models for the human-sensitive populations based on the relationship of the parameters in the validated rat and human models. Either approach can be used to perform the needed dosimetry. However, the second approach provides the advantage of a preliminary human life stage-specific PBPK model that can be used for identification of key data gaps and estimation of uncertainty.

Age Factors↗
PubMed2005

[Intrathyroidal iodine concentration after application of non-ionic contrast media with and without prophylactic application of perchlorate].

AIM: This study was designed to show the effect of a nonionic contrast medium (Iomeprol-300; CM) on the intrathyroidal iodine concentration with and without a concomitant medication with perchlorate (1380 mg/d) to block the thyroidal iodine uptake. VOLUNTEERS AND METHODS: Twelve volunteers recieved 100 ml Iomeprol-300 intravenously and the perchlorate prophylaxis mentioned above. Another 12 volunteers got 100 ml Iomeprol-300 only. By means of X-ray-fluorescence-analysis the intrathyroidal iodine concentration was determined in advance as well as 0.2, 1, 3, 5, 7, 24, 48, 72, and 96 hours after the application of the CM. RESULTS, CONCLUSION: The intrathyroidal iodine concentration did not change in the group of volunteers on perchlorate medication. Without perchlorate the intrathyroidal iodine concentration decreased after the application of the CM when it was initially high (722 +/- 66 microg/ml before, 670 +/- 65 microg/ml after CM; p = 0.046) and increased in case of a low initial concentration (327 +/- 40 microg/ml before, 381 +/- 25 microg/ml after CM; p = 0.046). The effect is significant but its magnitude is too small to be harmful for a patient with a healthy thyroid. The oral application of 1.4 g/d perchlorate inhibits the thyroidal iodine uptake and the intrathyroidal iodine concentration is unaffected by the application of a CM.

Adult↗