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Th.--Pharm.--Paris, 1857?

Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1911. / The entire thesis text is included in file. Typescript. Illustrated by author. Title from title screen of thesis/dissertation PDF file (viewed March 5, 2009)

This study investigated human exposure to inorganic arsenic (As), a risk factor for cancer and non-cancerous health effects, in Cornwall, UK - a region of elevated environmental As resulting from naturally occurring mineralisation and historical mining. Recent exposures to As from private water supplies (PWS) were detected by measuring As in drinking water samples (n=127) and urine samples (n=207). Exceedances of the WHO 10 As µg L-1 guidance value were measured in drinking waters from 5 % of households. The Spearman correlation calculated for drinking water versus unadjusted total urinary As concentrations was 0.36. Urinary As speciation was used to distinguish between environmental inorganic As exposure and non-toxic dietary sources. Seafood derived urinary arsenobetaine exclusion and osmolality hydration adjustment yielded an improved correlation of 0.62 between drinking water and urinary As concentrations. Urinary hydration adjustment methods were improved and comparatively assessed using data from the US National Health and Nutrition Examination Survey (NHANES). Correlations of urinary concentrations of As, iodine (I), lead (Pb) and cadmium (Cd) against urinary flow rate (UFR) (low correlations desired) and urinary Pb and Cd against respective blood concentrations (high correlations desired) were used as independent performance criteria. Osmolality adjustment and a modified UFR-based adjustment method using empirically derived coefficients (slopes of analyte concentrations as a function of UFR) generally performed better than creatinine, excretion rate and bodyweight-adjusted excretion rate methods. The findings demonstrated the analyte specific nature of adjustment methods, their misuse in the literature and suggested a pathway to a more robust adjustment framework. Prolonged exposure to As from PWS was identified by the stability of 127 drinking water As concentrations measured up to 31 months apart. Drinking water As concentrations were correlated with those measured in toenails (Pearson's r: 0.53; n=200) and hair (Pearson's r: 0.38; n=104). The successful elimination of external contamination of toenail samples was indicated by low As concentrations in final-stage rinse solutions (geometric mean contribution: 0.4 %). A positive association between seafood consumption and toenail As and a negative association between home-grown vegetable consumption and hair As was observed when As in drinking water was < 1 As μg/L. Elevated As concentrations measured in residential soil (12-992 mg kg-1; n=127) and household dust (3-1079 mg kg-1; n=99), particularly on mineralised geological domains and in the vicinity of former As mining sites, were indicative of additional As exposure routes. Bioaccessibility-adjusted assessment criteria of 190 (13 % bioaccessibility) and 129 (23 % bioaccessibility) As mg kg-1 were derived and 10 and 17 % of residential soils were in exceedance, respectively. The relative importance of different exposure routes in the study region, namely whether As intake from soil and dust is evident in the study population, will form the basis of further work. This will be addressed using multivariate analyses of drinking water, soil and dust in conjunction with urine, toenail and hair As concentrations.

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Over a hundred million people across the globe, and particularly in Asia, are chronicallyexposed to high concentrations (>10 ppb) of geogenic arsenic (As) in shallow reducinggroundwaters utilised as drinking water. It is widely accepted that As mobilisation fromsediments into these groundwater requires active metal-reducing microbes and electrondonors such as organic matter (OM). Although OM have been characterised in fewaquifers, there is a dearth of data on other As rich aquifers.In this work, we further investigate the correlation between As release from aquifers andthe OM/microbial communities present. The key findings of this work are:i. OM in Vietnamese and Taiwanese As hotspot areas originates from multiple sources.This is comparable to previous studies in Cambodia and West Bengal, indicating thatOM originates from similar sources in all the areas studied up to date, regardless ofthe age (Holocene/Pleistocene) and the sediment source (Himalayas/non-Himalayas).This suggests that similar electron donors, such as petroleum derived HMW nalkanes,are present in all these groundwater aquifer sediments.ii. No noticeable differences in OM biomarker distribution patterns were observedbetween sediments from two contrasting groundwater As concentration sites (e.g. <10 ppb; Pleistocene and up to 600 ppb; Holocene) in Vietnam, suggesting thatarsenic mobilisation is not associated with a specific OM source at these sites. Inaddition, no microbial activity was determined in these two sites suggesting thatother abiotic factors could lead to As release.iii. Microbiological process of dissimilatory As(V) reduction is active in microcosmexperiments using non-Himalayan Taiwanese sediments, despite low groundwaterAs concentrations, causing the release of As into the groundwater. However, Asrelease in these sediment slurries is not controlled by a specific source of the lipidderived OM, suggesting that other electron donors, not analysed in present studycould be contributing/controlling the rate of As release; and/or that multiple fractionsof the lipid derived OM are used as electron donors in this process.iv. Artificial maturation experiments indicated that a fully 13C-lablled kerogen analoguecan be obtained by using 13C-labelled cyanobacteria biomass as a starting material.However, this kerogen analogue had some differences when compared to the naturalmaterial, suggesting that an artificial degradation precursor step, prior to the actualmaturation process, might be required to generate analogues that better resemble thenatural kerogen.v. 13C-labelled substrates (hexadecane and kerogen) incubation experiments revealedthat As(III) release in all microcosms was microbially driven. Very low 13C-n-alkaneincorporation was observed in association with As release, suggesting that otherelectron donors could be mediating this process. In contrast, kerogen did not haveany effect on As release. Moreover, As(V) amendments enhanced the degradation ofthe shorter carbon chain length n-alkanes more than the longer ones, suggesting thatthese are more important electron donors in the process of As release than the longerones.

There is not, at this time, a simple method for the simultaneous determination of As (III) and As (V) at trace levels. The development of such as method is needed, as the toxicities of these two species differ so greatly. As (III) and As (V) are polarographically reducible in the presence of excess catechol, but the wave produced by As (V) is depended on time, pH and catechol concentration as well as As (V) concentration. In order to understand this behavior, determination of formation constants for any complex species present were needed to identify which species is electroactive. The literature to date on the subject of As (V) – catechol compounds has shown that there is not a thorough understanding of what species are present and what their stabilities are.

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