Perchlorate, exposure

Breast milk During lactation human mammary tissue expresses the sodium iodide symporter [260], and thus significant transfer of perchlorate into human milk is likely. The presence of micrograms per liter concentrations of perchlorate in milk collected fi om US women [233] confirms lactation as a relevant perchlorate excretion path. If lactating women are secreting perchlorate in milk, then urine-based estimates of total perchlorate exposure for these individuals are likely to be lower than actual [242]. 

Studies of low-dose perchlorate exposure in healthy human subjects A small number of studies have been published investigating the effects of low doses of perchlorate in thyroid function in healthy adults (without thyroid disease). One study was conducted in healthy male volunteers, involving the administration of 10 mg of perchlorate in drinking water for 14 days. A significant decrease in the uptake of iodine by the thyroid was observed at this dose, but there was no evidence of adverse effects on thyroid hormones or TSH concentrations [262]. Another recent study was conducted in healthy adults to determine the highest dose of perchlorate at which there is no effect on the uptake of iodine by the thyroid gland [263]. 

Blount BC, Valentin-Blasini L, Osterloh JD, Mauldin JP, Pirkle JL (2007) Perchlorate exposure of the US Population, 2001-2002. J Exp Sci Environ Epidemiol 17 400-407... 

Borjian M, Marcella S, Blount B, Greenberg M, Zhang J, Murphy E, Blasini VE, Robson M (2011) Perchlorate exposure in lactating women in an urban community in New Jersey. Sci Total Environ 409 460 64... 

Braverman LE, Pearce EN, He X, Pino S, Seeley M, Beck B (2006) Effects of six months of daily low-dose perchlorate exposure on thyroid funct ion in healthy volunt eers. J Clin Endocrinol Metab 91 2721-2724... 

Kelsh MA, Buffler PA, Daaboul JJ, Rutherford GW, Lau EC, Barnard JC, Exuzides AK, Madl AK, Palmer LG, Lorey FW (2003) Primary congenital hypothyroidism, newborn thyroid function, and environmental perchlorate exposure among residents of a Southern California community. J Occup Environ Med, 45 1116-1127. 

Another 14 day study employed 10 subjects (5 male/5 female) for each dose (0.5, 0.1, 0.02, and 0.007mgkg day ) who also served as their own control. The parameters measured were iodide-123 uptake in the thyroid for inhibition data and iodide and perchlorate in blood and urine for kinetic data. There were no changes seen in TSH or thyroid hormone levels in the blood. The result of the iodide inhibition measurements was a NOAEL of 0.007 mg kg day resulting in 4.8% iodide inhibition (equivalent to 0.5 mg day perchlorate exposure). Data from these studies were used to develop the human PBPK model for perchlorate. 

We and others have reported a series of studies in ammonium perchlorate production workers who are exposed intermittently to perchlorate, resulting in urine perchlorate values of up to 40 mg daily, and in normal volunteers given 3—3 5 mg perchlorate daily for 2 weeks or 0.5 and 3mg daily for 6 months (Lawrence et al, 2000, 2001 Greer et al., 2002 Gibbs et al., 1998 Braverman et al, 2005, 2006). Thyroid function studies, including serum TSH, thyroxine (T4), free T4, and total triiodothyronine (T3), were not affected by perchlorate exposure in the plant or perchlorate administration to normal volunteers, despite a decrease in the thyroid uptake of at the higher exposures. Despite a mean exposure of 3 years to high levels of perchlorate in the production workers, no abnormalities of the thyroid evaluated by ultrasound were detected compared to a nonexposed local population (Braverman etal., 2005). 

Ketoamides can participate in a variation of the Paal-Knorr condensation to yield 5-alkyl-2-aminofurans. Boyd described the cyclization of 1,4-ketoamides 91 upon exposure to acetic anhydride and perchloric acid to yield imminium salts 92 that furnished aminofurans 93 after treatment with triethylamine. ... 

The next major obstacle is the successful deprotection of the fully protected palytoxin carboxylic acid. With 42 protected functional groups and eight different protecting devices, this task is by no means trivial. After much experimentation, the following sequence and conditions proved successful in liberating palytoxin carboxylic acid 32 from its progenitor 31 (see Scheme 10) (a) treatment with excess 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (DDQ) in ie/t-butanol/methylene chloride/phosphate buffer pH 7.0 (1 8 1) under sonication conditions, followed by peracetylation (for convenience of isolation) (b) exposure to perchloric acid in aqueous tetrahydrofuran for eight days (c) reaction with dilute lithium hydroxide in H20-MeOH-THF (1 2 8) (d) treatment with tetra-n-butylammonium fluoride (TBAF) in tetrahydrofuran first, and then in THF-DMF and (e) exposure to dilute acetic acid in water (1 350) at 22 °C. The overall yield for the deprotection sequence (31 —>32) is ca. 35 %. 

A final category of encapsulating materials consists of reaction products of the nucleus material and a reagent. For example, pellets of nitronium perchlorate have been encapsulated in shells of the less reactive amm perchlorate (AP) by exposing the pellets to ammonia gas. The fragile AP shells were usually further protected by a top-coating of A1 or a polymer film (Ref 2). The most familiar example of this process is the natural one wherein A1 powders (or articles) become coated with a protective coating of A1 oxide thru exposure to atmospheric air... 

Microencapsulation is usually attempted because a proposed ingredient is too reactive or too sensitive to withstand exposure to other ingredients nr tQ the environment. For example, the very energetic oxidizer nitronium perchlorate (NP) cannot be mixed directly into a proplnt or expl formulation because of its extreme reactivity. It is actually a solid anhydride between nitric and perchloric acids, and even traces of moisture hydrolyze the surface layers to free coned nitric... 

Organophosphates, such as methyl parathion, are known to inhibit cholinesterase activity. A method has been developed to measure the extent of this inhibition and relate it to organophosphate exposure (EPA 1980d Nabb and Whitfield 1967). In this EPA-recommended method, blood is separated into plasma and red blood cell fractions. The fractions are treated with saline solution, brought to pH 8 with sodium hydroxide, and dosed with acetylcholine perchlorate. The ensuing acetic acid releasing enzyme reaction... 

Though formazans can be protonated, there are no reports of isolation of formazan cations. The study of the basicity of formazans is complicated by the fact that exposure to acid can lead to irreversible chemical changes. Recently, the protonation of the triaryl formazan 194 with perchloric acid in aprotic solvents has been studied spectroscopically. In this a hypso-chromic shift is observed and is more pronounced when X is an electron-donating substituent. Thus, the shift is 33, 14, and 73nm when X is hydrogen, /Mnethoxy, and w-nitro, respectively.337... 

A powerful oxidant which may explode above 80°C, and which ignites organic solvents on contact. It decomposes, sometimes explosively, on exposure to light. See Other METAL PERCHLORATES, OXIDANTS... 

Despite the latent reactivity of ketene thioacetals,3-4 some members of this class such as the title compound have been little studied, perhaps because of preparative inaccessibility. The only previously reported route to 2-methylene-1,3-dlthiolane involves monoacetylation of 1,2-ethanedithiol, cyclization to 2-methyl-1,3-dithiolan-2-yl perchlorate, and exposure of this salt to diisopropylethylamine in acetonitrile 5... 

Enantioselective [2 + 2 cycloaddition.2 The chiral allylic ether (1), prepared from (lS,2R)-( + )-2-phenylcyclohexanol, undergoes enantioselective cycloaddition with dichloroketene to furnish, after one crystallization, optically pure (-)-2. This cyclobutanone after ring expansion and exposure to chromium(II) perchlorate gives... 

The need for great care to avoid the possibility of detonation of perchloryl compounds by exposure to shock, overheating or sparks is stressed. The compounds are generally more sensitive to impact than mercury fulminate and are of comparable sensitivity to lead azide [1], A range of highly explosive alkyl perchlorates [2] and perchlorylamines [3] have been prepared by interaction of dichlorine heptaoxide with alcohols or amines in carbon tetrachloride solution. The solutions of the products were not sensitive to mechanical shock and could... 

Abstract We have reviewed the human exposure to selected emerging organic contaminants, such new brominated flame retardants, organophosphate flame retardants, phthalate substitutes, triclosan, synthetic musks, bisphenol-A, perchlorate, and polycyclic siloxanes. Levels of these emerging contaminants in matrices relevant for human exposure (air, dust, food, water, etc.) and in human matrices (blood, urine, or tissues) have been reviewed, together with some of the relevant health effects reported recently. 

Exposure of humans to perchlorate via foodstuffs and drinking water has been documented [241]. Urine, breast milk, amniotic fluid, saliva, and blood have been used as matrices in biomonitoring of human exposures to perchlorate [233, 242-253] (Table 10). Assessment of human exposures to perchlorate is important, since this compound blocks iodine uptake in the thyroid gland, which can lead to a decrease in the production of thyroid hormones (T3 and T4) essential for neurodevelopment [260]. 

Urine Urine is the principal route by which nonlactating humans excrete perchlorate [261, 262]. Urinary perchlorate provides a reasonable measure of human exposure because 70-95% of perchlorate dose is excreted unchanged in the urine with a half-life of 8 h [261-263]. Creatinine (CR) adjustment is typically used to minimize the effects of variation of analyte concentration in urine either among samples produced by different individuals or among samples produced by the same individual. 

Amitai Y, Winston G, Sack J, Wasser J, Lewis M, Blount BC, Valentin-Blasini L, Fisher N, Israeli A, Leventhal A (2007) Gestational exposure to high perchlorate concentrations in drinking water and neonatal thyroxine levels. Thyroid 17 843-850... 

Blount BC, Rich DD, Valentin-Blasini L, Lashley S, Ananth CV, Murphy E, Smulian JC, Spain BJ, Barr DB, Ledoux T (2009) Perinatal exposure to perchlorate, thiocyanate, and nitrate in New Jersey mothers and newhoms. Environ Sci Technol 43 7543-7549... 

Tellez R, Chacon PM, Crump KS, Blount BC, Gibbs JP (2005) Chronic environmental exposure to perchlorate through drinking water and thyroid function during pregnancy and the neonatal period. Thyroid 15 963-975... 

Gibbs JP, Ahmad R, Crump KS, Houck DP, Leveille TS, Findley JE, Francis M (1998) Evaluation of a population with occupational exposure to airborne ammonium perchlorate for possible acute or chronic effects on thyroid function. J Occup Environ Med 40 1072-1082... 

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