Arsenic risk assessment.

Abstract

In this commentary, we respond to the conclusions of recent publications by (7,8) * The authors used urinary arsenic concentrations from grab samples as the basis for evaluating methylating capacity. However, the proportion of inorganic arsenic excreted in the urine varies substantially over time; thus, an individual grab sample is not representative of the degree of methylation that is occurring. Studies by Buchet et al. (6) show that after ingestion of inorganic arsenic, the proportion of arsenic in the urine that is inorganic arsenic is high soon after exposure (0-12 hr), but much lower later on (>12 hr). The appropriate measurement with which to examine metabolism and elimination of arsenic is the total mass of inorganic arsenic and its metabolites eliminated over a 24-to 48-hr time period; using mass per time rather than concentration would control not only for variability in the proportions of the metabolites over the course of a day, but also for variability in urine volume. A recent 7-day diet study in Japan found that the intake and excretion of total arsenic were balanced when averaged over a week but not over 1 day (9). Smith et al. Currently, the CSF for ingested arsenic is based on the incidence of nonmelanoma skin cancers associated with exposure to high levels of arsenic in drinking water in Taiwan; however, Smith et al. have suggested that arsenic could be an important risk factor not only for skin cancer, but also for several internal cancers including lung, liver, bladder, and kidney. Smith et al. used the data from another epidemiological study in Taiwan (10) to examine

In Vivo Effects of Arsenite on Meiosis, Preimplantation Development, and Apoptosis in the Mouse1

“…Although water supplies in the United States are generally low in arsenic, there have been reports of arsenic contamination of groundwater in the Southwest, with levels in the hundreds and, in few cases, more than 1,000 g/L [7,8]. Moreover, arsenic is a contaminant at a number of sites on the U.S. National Priorities List of hazardous waste sites [9] and the U.S. Environmental Protection Agency has placed arsenic at the top of its Superfund Contamination List [10].…”

Dose-Dependent Effects on the Disposition of Monomethylarsonic Acid and Dimethylarsinic Acid in the Mouse After Intravenous Administration

“…What we may have observed is inhibition or saturation of arsenic methylation. However, whether this occurs, especially in humans, is very controversial (Petito & Beck, 1990;Hopenhayn-Rich et al, 1993;Carlson-Lynch et al, 1994;Beck et al, 1995;Smith et al, 1995).…”

Arsenic, cadmium, mercury and nickel stimulate cell growth via NADPH oxidase activation

“…Strong epidemiological and experimental data support the fact that As exposure causes several types of cancers including skin, urinary tract and lung cancers [3]. Stimulation of cancer stem cell proliferation has been suggested to mechanistically explain how As promotes tumor formation [4].…”