Tissue distribution and urinary excretion of inorganic arsenic and its methylated metabolites in C57BL6 mice following subchronic exposure to arsenate in drinking water.

The relationship of exposure and tissue concentration of parent chemical and metabolites over prolonged exposure is a critical issue for chronic toxicities mediated by metabolite(s) rather than parent chemical alone. This is an issue for AsV because its trivalent metabolites have unique toxicities and relatively greater potency compared to their pentavalent counterparts for many endpoints. In this study, dose-dependency in tissue distribution and urinary excretion for inorganic arsenic and its methylated metabolites was assessed in female C57Bl/6 mice exposed to 0, 0.5, 2, 10 or 50 ppm arsenic (as arsenate, AsV) in their drinking water for 12 weeks. No adverse effects were observed and body weight gain did not differ significantly among groups. Urinary excretion of arsenite monomethylarsonous acid (MMA(III)), dimethylarsinous acid (DMA(III)), dimethylarsinic acid (DMAV), and trimethylarsine oxide (TMAO) increased linearly with dose, whereas AsV and monomethylarsonic acid (MMAV) excretion was non-linear with respect to dose. Total tissue arsenic accumulation was greatest in kidney > lung > urinary bladder >>> skin > blood > liver. Monomethyl arsenic (MMA, i.e. MMA(III)+MMAV) was the predominant metabolite in kidney, whereas dimethylarsenic (DMA, i.e., DMA(III)+DMAV) was the predominant metabolite in lung. Urinary bladder tissue had roughly equivalent levels of inorganic arsenic and dimethylarsenic, as did skin. These data indicate that pharmacokinetic models for arsenic metabolism and disposition need to include mechanisms for organ-specific accumulation of some arsenicals and that urinary metabolite profiles are not necessarily reflective of target tissue dosimetry.

Systemic uptake of inhaled arsenic in rabbits.

Human occupational exposure to sufficiently high levels of arsenic in air has been associated with lung cancer, but generally not other types of cancer. Thus, a better understanding of the relationship between airborne arsenic exposures and systemic uptake is essential. In this study, rabbits were exposed to one of four levels of arsenic trioxide in air for 8 h/day, 7 days/week, for 8 weeks (0.05, 0.1, 0.22, or 1.1 mg/m3). Plasma levels of inorganic arsenic, monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) were measured following the last exposure. Although there was a dose-related increase in plasma levels of methylated arsenic metabolites, statistically significant increases in mean inorganic arsenic levels in plasma were observed only in male rabbits exposed to 0.22 mg/m3, and in both males and females exposed to 1.1 mg/m3. Mean inorganic arsenic levels in plasma in males and females exposed to 0.05 and 0.1 mg/m3, and females exposed to 0.22 mg/m3, were not significantly elevated compared to controls. These results suggest that arsenic inhalation has a negligible impact on body burden of inorganic arsenic until air levels are significantly elevated. Based on plasma measurements of inorganic arsenic, the two lowest exposure levels in this study (0.05 and 0.1 mg/m3) are indistinguishable from background.

A market basket survey of inorganic arsenic in food.

Dietary arsenic intake estimates based on surveys of total arsenic concentrations appear to be dominated by intake of the relatively non-toxic, organic arsenic forms found in seafood. Concentrations of inorganic arsenic in food have not been not well characterized. Accurate dietary intake estimates for inorganic arsenic are needed to support studies of arsenic's status as an essential nutrient, and to establish background levels of exposure to inorganic arsenic. In the market basket survey reported here, 40 commodities anticipated to provide at least 90% of dietary inorganic arsenic intake were identified. Four samples of each commodity were collected. Total arsenic was analysed using an NaOH digestion and inductively coupled plasma-mass spectrometry. Separate aliquots were analysed for arsenic species using an HCl digestion and hydride atomic absorption spectroscopy. Consistent with earlier studies, total arsenic concentrations (all concentrations reported as elemental arsenic per tissue wet weight) were highest in the seafoods sampled (ranging from 160 ng/g in freshwater fish to 2360 ng/g in saltwater fish). In contrast, average inorganic arsenic in seafood ranged from less than 1 ng/g to 2 ng/g. The highest inorganic arsenic values were found in raw rice (74 ng/g), followed by flour (11 ng/g), grape juice (9 ng/g) and cooked spinach (6 ng/g). Thus, grains and produce are expected to be significant contributors to dietary inorganic arsenic intake.

Separate dissolved and particulate trace metal budgets for an estuarine system: an aid for management decisions.

The sources and sinks of dissolved and particulate Pb, Cu and Zn were determined for the main basin of Puget Sound to understand the effect man has had on metal concentrations in both the water column and in the sediments. Municipal, industrial and atmospheric sources contributed about 66% of the total Pb added to the main basin of Puget Sound during the early 1980s. Advective inputs were the major sources of total Cu and Zn (approximately 40%) while riverine and erosional sources contributed about 30%. The discharge of the particle-bound trace metals from rivers minimized the influence of particulate anthropogenic sources, which constituted 50%, 23% and 18% of the total particulate Pb, Cu and Zn inputs, respectively. While advective transport was the major source of dissolved Cu and Zn (approximately 60% of all dissolved inputs), industrial, municipal and atmospheric inputs contributed about 85%, 30% and 38% of the dissolved Pb, Cu and Zn inputs, respectively. The sources of dissolved and particulate Cu and Zn were comparable with the sinks within the errors of the analyses indicating their quasi-conservative nature. Advection removed about 60% of the total Cu and Zn added to the main basin while 40% was deposited in the sediments of Puget Sound. Because of this quasi-conservative nature of Cu and Zn, anthropogenic inputs of Cu and Zn were dispersed from the system more than they were contained within main basin sediments. About 75% of the dissolved Pb discharged into the main basin of Puget Sound was lost from the dissolved phase and was balanced by a similar gain in the particulate phase. Because of this extensive scavenging and the effective retention of particles within the main basin, about 70% of the total Pb added to the main basin was retained within its sediments. These separate mass balances have utility in management decisions because they show the relative contributions from different sources and demonstrate whether the influences of dissolved and particulate inputs are reflected solely in the water column or the sediments, respectively.

Trace element content of moonshine.

Although the contamination of illicit whiskey with lead is widely accepted, the potential for exposure to other trace elements from drinking "moonshine" is less well appreciated. To better understand the potential for trace element poisoning, we undertook an analysis of samples of Georgia moonshine. Although a number of elements were not found in significant quantities to be considered harmful, four elements (copper, zinc, lead, and arsenic) were present in potentially toxic concentrations. The possible implications and sources of the contamination are discussed.

Moonshine-related arsenic poisoning.

Twelve sequential cases of arsenic poisoning were reviewed for possible sources of ingestion. Contaminated illicit whiskey (moonshine) appeared to be the source in approximately 50% of the patients. An analysis of.confiscated moonshine revealed that occasional specimens contained high levels of arsenic as a contaminant. Although arsenic poisoning occurs relatively infrequently, contaminated moonshine may be an important cause of the poisoning in some areas of the country.

Changes in the chemical speciation of arsenic following ingestion by man.

The concentrations of four chemical species of arsenic in urine were observed with time, after ingestion of three different chemical species of arsenic. The arsenic-rich substances ingested, including arsenite-rich wine, arsenate-rich drinking water, and crab meat which contained organo-arsenic compounds. After ingestion of arsenite-rich wine, approximately 10% of the arsenic was excreted as arsenite, but the majority of the arsenic was methylated to methylarsonic acid and dimethylarsinic acid and excreted. After ingestion of arsenate-rich water, elevated levels of both arsenate and dimethylarsinic acid were observed. When crab meat was ingested, none of these four arsenic species were observed at elevated levels until the urine was heated in 2N NaOH. After the hot base digestion, high levels of dimethylarsinic acid were detected in these samples. The apparent biological half-lives were on the order of 10 hr for inorganic arsenic and 30 hr for the methylated arsenic forms.

Airborne arsenic exposure and excretion of methylated arsenic compounds.

First void urine samples were collected from copper smelter workers exposed to inorganic arsenic and from unexposed controls. Arsenic compounds (As (III), As (V), methylarsonic acid and dimethylarsinic acid) in these samples were analyzed by selective volatilization as arsines with determination of arsenic by plasma excitation emission spectrometry. On the day preceding the urine sample collection a breathing zone measurement was made of respirable arsenic particulates for each subject. It was found that all of the subjects, including the controls excreted arsenic primarily as methylated species. Approximately 50% of the total arsenic was excreted as dimethylarsinic acid and 20% as methylarsonic acid. Slight differences in the proportion of various arsenic compounds were observed with varying levels of inorganic arsenic exposure. Amounts of arsenic species were all closely correlated with each other and with exposure. Irrespirable particulate exposures were measured on a subset of high exposure workers. Irrespirable arsenic was found to be more closely correlated with excretion of arsenic compounds than was respirable arsenic.

Mercury emissions from geothermal power plants.

Geothermal steam used for power production contains significant quantities of volatile mercury. Much of this mercury escapes to the atmosphere as elemental mercury vapor in cooling tower exhausts. Mercury emissions from geothermal power plants, on a per megawatt (electric) basis, are comparable to releases from coal-fired power plants.