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Perchlorate is a water soluble anion that is readily accumulated in vegetation. It inhibits uptake of iodide into thyroid gland tissue, thereby reducing production of thyroid hormones. Potential raccoon food items including berries, fish, and vegetation collected at a contaminated site contained quantifiable concentrations of perchlorate as determined by ion chromatography. Therefore, we monitored resident raccoons for exposure to perchlorate by examining plasma perchlorate and thyroid hormone concentrations. Resulting analytical data failed to demonstrate perchlorate exposure among raccoons that likely consumed food items collected along perchlorate-contaminated water bodies. There were no correlations between triiodothyronine or thyroxine and thyroid stimulating hormone concentrations, but triiodothyronine concentrations in raccoon plasma were significantly higher in 2000 than in 2001 (p = 0.0081). These data suggest that natural attenuation and remedial efforts initiated in January of 2001 may have reduced perchlorate exposure among raccoons inhabiting this site from 2000 to 2001. Temporal, spatial, and analytical factors limited our ability to quantify exposure among raccoons, however, our data do not indicate that raccoons currently inhabiting this site are at risk for significant exposure to perchlorate and subsequent effects.
Bis-(5-nitro-2H-tetrazolato-N2)tetraammine[cobalt(III)/nickel(III)] perchlorates (BNCP/BNNP) and mono-(5-nitro-H-tetrazolato-N)triammine [copper(II)/zinc(II)] perchlorates (MNCuP/MNZnP) have been synthesized during this work. The synthesis was carried out by addition of carbonato tetraammine metal [Co/Ni/Cu/Zn] nitrate [CTCN/CTNN/CTCuN/CTZnN] to the aqueous solution of sodium salt of 5-nitrotetrazole followed by reaction with perchloric acid. The precursors were synthesized by the reaction of aqueous solution of their respective nitrates with ammonium carbonate at 70 degrees C. The complexes and their precursors were characterized by determining metal and perchlorate content as well as infrared (IR), electron spectra for chemical analysis (ESCA) and X-ray diffraction (XRD) techniques. The TG profiles indicated that BNCP, BNNP and MNCuP are thermally stable up to the temperature of 260-278 degrees C unlike MNZnP (150 degrees C). Sudden exothermic decomposition was observed in case of bis-(5-nitro-2H-tetrazolato-N2)tetraammine cobalt(III) perchlorate, bis-(5-nitro-2H-tetrazolato-N2)tetraammine nickel(III) perchlorate and mono-(5-nitro-H-tetrazolato-N)triammine zinc(II) perchlorate resulting in the severe damage of the sample cup. Sensitivity data indicated that the Co/Ni/Cu complexes are more friction sensitive (3-4.8 kg) than mono-(5-nitro-H-tetrazolato-N)triammine zinc(II) perchlorate (14 kg). The impact sensitivity results of the complexes corresponded to h50% of 30-36 cm.
The reversed-phase liquid chromatography (RPLC) behavior of synthetic model peptides containing positively charged amino acid residues was studied in the presence or absence of 100 mM sodium perchlorate in order to determine the effect on apparent side-chain hydrophilicity of a charged residue at low pH. The peptides used in this study were either non-helical peptides or amphipathic alpha-helical peptides, where the effect of the negatively charged perchlorate ion on a charged residue in either the hydrophobic face or hydrophilic face of the helix was monitored. We have shown that the addition of 100 mM perchlorate to RPLC separations of positively charged peptides performed in a 20 mM aqueous phosphoric acid-acetonitrile system resulted in an increase in retention time of a peptide relative to the same peptide in the absence of perchlorate. This effect occurred independent of conformation, i.e., whether comparing the effect of positively charged residue substitutions in the hydrophobic or hydrophilic face of an amphipathic alpha-helix or in a peptide with negligible secondary structure. From these results, suggesting that positively charged side-chain hydrophilicity is decreased by ion-pairing with the perchlorate ion, we have shown practical examples where mixtures of non-helical and amphipathic alpha-helical peptides showed enhanced resolution in the presence of perchlorate at pH 2, compared to in its absence. In addition, it was shown that an aqueous phosphoric acid-perchlorate-acetonitrile mobile phase may show markedly different selectivity for peptide separations at low pH compared to the more traditional aqueous trifluoroacetic acid-acetonitrile system.
Human exposure to perchlorate is commonplace because it is a contaminant of drinking water, certain foods, and breast milk. The U.S. Environmental Protection Agency (EPA) conducted a perchlorate risk assessment in 2002 that yielded a reference dose (RfD) based on both the animal and human toxicology data. This assessment has been superceded by a recent National Academy of Science (NAS) review that derived a perchlorate RfD that is 20-fold greater (less stringent) than that derived by the U.S. EPA in 2002. The NAS-derived RfD was put on the U.S. EPA's Integrated Risk Information System (IRIS) database very quickly and with no further public review. In this commentary we raise concerns about the NAS approach to RfD development in three areas of toxicity assessment: the dose that the NAS described as a no observable adverse-effect level is actually associated with perchlorate-induced effects; consideration of uncertainties was insufficient; and the NAS considered the inhibition of iodine uptake to be a nonadverse effect. We conclude that risk assessors should carefully evaluate whether the IRIS RfD is the most appropriate value for assessing perchlorate risk.
Various published data sets that investigate the potential effect of exogenous perchlorate (ClO4-) on the uptake of iodide in the thyroid and subsequent changes in thyroid hormone levels are available. In order to best use the data towards the prediction of human health effects resulting from ClO4- exposure, the available literature data must be integrated into a self-consistent, coherent, and parsimonious quantitative model based on the most likely mode of action of perchlorate effect on thyroid function. We submit that the simplest mode of action for ClO4- in the thyroid that remains consistent with all available data involves competitive inhibition of iodide transport into the thyroid follicle, transport of perchlorate into the thyroid follicle against a concentration gradient, further transport into the thyroid lumen (where it may again interfere with iodide transport), and, finally, passive diffusion back into the blood. We believe this description of perchlorate's kinetic behavior should serve as the foundation for predictive physiologically based pharmacokinetic (PBPK) models and as a working hypothesis for further experimental exploration.
Detection of perchlorate (ClO4-) in several drinking water sources across the U.S. has lead to public concern over health effects from chronic low-level exposures. Perchlorate inhibits thyroid iodide (I-) uptake at the sodium (Na+)-iodide (I-) symporter (NIS), thereby disrupting the initial stage of thyroid hormone synthesis. A physiologically based pharmacokinetic (PBPK) model was developed to describe the kinetics and distribution of both radioactive I- and cold ClO4- in healthy adult humans and simulates the subsequent inhibition of thyroid uptake of radioactive I- by ClO4-. The model successfully predicts the measured levels of serum and urinary ClO4- from drinking water exposures, ranging from 0.007 to 12 mg ClO4-/kg/day, as well as the subsequent inhibition of thyroid 131I- uptake. Thyroid iodine, as well as total, free, and protein-bound radioactive I- in serum from various tracer studies, are also successfully simulated. This model's parameters, in conjunction with corresponding model parameters established for the male, gestational, and lactating rat, can be used to estimate parameters in a pregnant or lactating human, that have not been or cannot be easily measured to extrapolate dose metrics and correlate observed effects in perchlorate toxicity studies to other human life stages. For example, by applying the adult male rat:adult human ratios of model parameters to those parameters established for the gestational and lactating rat, we can derive a reasonable estimate of corresponding parameters for a gestating or lactating human female. Although thyroid hormones and their regulatory feedback are not incorporated in the model structure, the model's successful prediction of free and bound radioactive I- and perchlorate's interaction with free radioactive I- provide a basis for extending the structure to address the complex hypothalamic-pituitary-thyroid feedback system. In this paper, bound radioactive I- refers to I- incorporated into thyroid hormones or iodinated proteins, which may or may not be bound to plasma proteins.
The perchlorate (ClO4(-))-respiring organism, strain perclace, can grow using nitrate (NO3(-)) as a terminal electron acceptor. In resting cell suspensions, NO(-) grown cells reduced ClO4(-), and ClO4(-) grown cells reduced NO3(-). Activity assays showed that nitrate reductase (NR) activity was 1.31 micromol min(-1) (mg protein)-1 in (ClO4)- grown cells, and perchlorate reductase (PR) activity was 4.24 micromol min(-1) (mg protein)(-1) in NO3(-) grown cells. PR activity was detected within the periplasmic space, with activities as high as 14 pmol min(-1) (mg protein)(-1). The NR had a pH optimum of 9.0 while the PR had an optimum of 8.0. This study suggests that separate terminal reductases are present in strain perclace to reduce NO3(-) and ClO4(-).
The crystal structures of a pair of closely related macrocyclic cyano- and hydroxopentaaminecobalt(III) complexes, as their perchlorate salts, are reported. Although the two complexes, [Co(CN)(C(11)H(27)N(5))](ClO(4))(2).H(2)O and [Co(OH)(C(11)H(27)N(5))](ClO(4))(2), exhibit similar conformations, significant differences in the Co-N bond lengths arise from the influence of the sixth ligand (cyano as opposed to hydroxo). The ensuing hydrogen-bonding patterns are also distinctly different. Disorder in the perchlorate anions was clearly resolved and this was rationalized on the basis of distinct hydrogen-bonding motifs involving the anion O atoms and the N-H and O-H donors.
Perchlorate (ClO4-) contamination of ground water is a widespread problem in the U.S., which can adversely affect human health and wildlife. Current methods for detecting and quantifying ClO4- in water are time consuming, expensive and sometimes subject to complex procedures. This study reports the construction of a ClO4- reductase-based biosensor for rapid determination of ClO4- in water. Using a 3 mm GCE (glass carbon electrode), a ClO4- sensing bio-electrode was constructed by coating an aliquot of a Dechlorosoma sp. ClO4- reductase on nafion (ion-exchange matrix) layer pre-coated on the polished surface of the GCE. The response time to ClO4- was approximately 111+/-28 s. Kinetic evaluation of the sensor response to ClO4- revealed linear increases (r2>99%) in 10 min with k values of 10.3, 24.2, 33.9 and 48.2 at 25, 50, 75 and 100 microg/L, respectively. A strong linear correlation was established between biosensor response (nA) and ion-chromatography conductivity readings (microS). Biosensor response to ClO4- was maximal at applied potential range of -0.6 to -1.0 V. ClO4- reduction was maximal in the range of 7.6 to 8.0. The ClO4- biosensor was significantly stable after repeated use (24 analyses conducted on day 1 over a 10-h period at room temperature). This study indicates great potential for the development of a portable biosensor for real time analysis of ClO4- in water.
Perchlorate (ClO4-) is a major ground water pollutant of public health concern. ClO4- reductase is the key enzyme in the pathway of ClO4- breakdown. ClO4- reductase from cell-free extracts of the ClO4- -respiring bacterium perc lace was purified 10-fold by ion-exchange and molecular exclusion fast protein liquid chromatography (FPLC). The ClO4- reductase catalyzed the reduction of ClO4- at a Vmax and Km of 4.8 U mg protein(-1) and 34.5 microM, respectively. ClO4- reduction was achieved in the temperature range of 20 to 40 degrees C and with optimum activity at 25 degrees C to 30 degrees C and pH 7.5 to 8.0. Molecular masses of two subunits of ClO4- reductase were determined by SDS-PAGE to be 35 kDa and 75 kDa. MALDI-TOF/MS analysis of a trypsin digest of the 35 kDa subunit, revealed several tryptic peptides. Amino acid sequences of 22 tryptic peptides of the 35 kDa ClO4- reductase subunit were obtained by electrospray mass spectrometry. GenBank protein Blast analysis of the amino acid sequences revealed relevant similarity to reductases, dehydrogenases and heme proteins. Data obtained are useful towards the identification of the overall genetic determinants of ClO4- reduction and specific in situ detection of ClO4- as well as NO3-reducing bacteria in ground water.
Perchlorate (ClO4-) disrupts endocrine homeostasis by competitively inhibiting the transport of iodide (I-) into the thyroid. The potential for health effects from human exposure to ClO4- in drinking water is not known, but experimental animal studies are suggestive of developmental effects from ClO4- induced iodide deficiency during gestation. Normal hormone-dependent development relies, in part, on synthesis of hormones in the fetal thyroid from maternally supplied iodide. Although ClO4- crosses the placenta, the extent of inhibition in the fetal thyroid is unknown. A physiologically-based pharmacokinetic (PBPK) model was developed to simulate ClO4- exposure and the resulting effect on iodide kinetics in rat gestation. Similar to concurrent model development for the adult male rat, this model includes compartments for thyroid, stomach, skin, kidney, liver, and plasma in both mother and fetus, with additional compartments for the maternal mammary gland, fat, and placenta. Tissues with active uptake are described with multiple compartments and Michaelis-Menten (M-M) kinetics. Physiological and kinetic parameters were obtained from literature and experiment. Systemic clearance, placental-fetal transport, and M-M uptake parameters were estimated by fitting model simulations to experimental data. The PBPK model is able to reproduce maternal and fetal iodide data over five orders of magnitude (0.36 to 33,000 ng/kg 131I-), ClO4- distribution over three orders of magnitude (0.01 to 10 mg/kg-day ClO4-) and inhibition of maternal thyroid and total fetal I- uptake. The model suggests a significant fetal ClO4- dose in late gestation (up to 82% of maternal dose). A comparison of model-predicted internal dosimetrics in the adult male, pregnant, and fetal rat indicates that the fetal thyroid is more sensitive to inhibition than that of the adult.
Perchlorate (ClO(4)(-)) and thiocyanate (SCN(-)) are potent and nitrate (NO(3)(-)) a weak competitive inhibitor of the thyroid sodium-iodide symporter. To determine the effects of long-term, high ClO(4)(-) exposure on thyroid function, we conducted a study of 29 workers employed for at least 1.7 yr (50% over 5.9 yr) in an ammonium ClO(4)(-) production plant in Utah. Serum ClO(4)(-), SCN(-), and NO(3)(-); serum T(4), free T(4) index, total T(3), thyroglobulin (Tg), and TSH; 14-h thyroid radioactive iodine uptake (RAIU); and urine iodine (I) and ClO(4)(-) were assessed after 3 d off (Pre) and during the last of three 12-h night shifts in the plant (During) and in 12 volunteers (C) not working in the plant. Serum and urine ClO(4)(-) were not detected in C; urine ClO(4)(-) was not detected in 12 of 29 and was 272 microg/liter in 17 Pre workers; serum ClO(4)(-) was not detected in 27 of 29 Pre; and serum and urine ClO(4)(-) were markedly elevated during ClO(4)(-) exposure to 868 microg/liter and 43 mg/g creatinine, respectively. Serum SCN(-) and NO(3)(-) concentrations were similar in all groups. Thyroid RAIUs were markedly decreased in During compared with Pre (13.5 vs. 21.5%; P < 0.01, paired t) and were associated with an increase in urine I excretion (230 vs. 148 microg I/g Cr; P = 0.02, paired t) but were similar to those in the C group (14.4%). Serum TSH and Tg concentrations were normal and similar in the three groups. Serum T(4) (8.3 vs. 7.7 microg/dl), free T(4) index (2.4 vs. 2.2), and total T(3) (147 vs. 134 ng/dl) were slightly but significantly increased in the During vs. Pre workers (P < 0.01, paired t). Thyroid volumes and patterns by ultrasound were similar in the 29 workers and 12 community volunteers. In conclusion, high ClO(4)(-) absorption during three nights work exposure decreased the 14-h thyroid RAIU by 38% in ClO(4)(-) production workers compared with the RAIU after 3 d off. However, serum TSH and Tg concentrations and thyroid volume by ultrasound were not affected by ClO(4)(-), suggesting that long-term, intermittent, high exposure to ClO(4)(-) does not induce hypothyroidism or goiter in adults.
The concentrations of 36Cl-labeled potassium perchlorate (K36CiO4) and previously reported iodide (131I) in the ova, thyroid gland, and blood of the laying hen were compared in this investigation. Radioperchlorate concentration and deposition properties showed a remarkable resemblance to those of iodide (131I). The topographic distribution of radioperchlorate in ova followed a peripheral and concentric ring deposition identical to that observed in the 131I investigation. The studies of the distribution of radioperchlorate showed that about 10.3, 2.0, and 1.4% of a single intramuscular injection of K36CiO4 was retained in the body at 3, 24, and 48 hours, respectively. The largest total concentration in the 3-hour group was found in the blood (2.9%), followed by muscles (2.4%), internal organs (1.1%), and the 10 largest ova (1.0%). The 24 and 48-hour hens' ova showed the largest concentrations with values of 1.5 and 1.2% of the dose, respectively. This represented 76.9 and 81.3% of the total activity retained in the body at these times. The excreta in the 3 and 24-hour experiments accounted for most of the radioperchlorate dose.
(Tb1-x Tmx).L2.(ClO4).2H2O(x = 0.000 to 0.200, L = C6H5SOCH2COO-) have been synthesized. The coordination compounds have been studied by means of composition analysis, molar conductivity, IR, and the condition of coordination have been inferred. In the fluorescent spectra it was found that Tm3+ has a strongly sensitization effect to the fluorescence of Tb3+. The fluorescent emission intensity of Terbium perchlorate with phenylcarboxymethyl sulfoxide coordination compounds would be enhanced by Tm3+ in mixing. Tm3+ has a sensitization to the fluorescence of Tb3+ in the ratio of Tb3+:Tm3+ = 0.999:0.001-0.900:0.100. In the solubility experiment it was found that the complexes have high solubility in ethanol.
The title complex, bis[3,3'-(pyridine-4-imino-kappaN(1))dipropanenitrile]silver(I) perchlorate, [Ag(CEAP)(2)]ClO(4) (CEAP is 4-[N,N-bis(2-cyanoethyl)amino]pyridine, C(11)H(12)N(4)), has been prepared and characterized. The unit cell consists of two crystallographically non-equivalent molecules. Cation cavities are constructed by [Ag(CEAP)(2)](+) cations through hydrogen bonds, and the ClO(4)(-) anions are incorporated into the cavities in mu(4)- and mu(2)-ClO(4)(-) bridging modes through C-H.O hydrogen bonds.
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