Toenails as a Biomarker of Inorganic Arsenic Intake From Drinking Water and Foods

Abstract

Toenails were used recently in epidemiological and environmental health studies as a means of assessing exposure to arsenic from drinking water. While positive correlations between toenail and drinking-water arsenic concentrations were reported in the literature, a significant percentage of the variation in toenail arsenic concentration remains unexplained by drinking-water concentration alone. Here, the influence of water consumption at home and work, food intake, and drinking-water concentration on toenail arsenic concentration was investigated using data from a case-control study being conducted in 11 counties of Michigan. The results from 440 controls are presented. Log-transformed drinking-water arsenic concentration at home was a significant predictor (p < .05) of toenail arsenic concentration (R2 = .32). When arsenic intake from consumption of tap water and beverages made from tap water (microg/L arsenic x L/d = microg/d) was used as a predictor variable, the correlation was markedly increased for individuals with >1 microg/L arsenic (R2 = .48). Increased intake of seafood and intake of arsenic from water at work were independently and significantly associated with increased toenail arsenic concentration. However, when added to intake at home, work drinking-water exposure and food intake had little influence on the overall correlation. These results suggest that arsenic exposure from drinking-water consumption is an important determinant of toenail arsenic concentration, and therefore should be considered when validating and applying toenails as a biomarker of arsenic exposure.

Urinary arsenic species, toenail arsenic, and arsenic intake estimates in a Michigan population with low levels of arsenic in drinking water

“…To assess different exposure levels, we grouped individuals according to arsenic concentrations in water: total population (n ¼ 343) and individuals with greater than 1 mg arsenic per l water (n ¼ 137). This grouping was also performed for comparison with previous studies (Karagas et al, 2002;Slotnick et al, 2007). Individuals were further stratified in terms of water intake (plain water plus beverages made with tap water from home); intake was categorized as either greater than or less than the median water intake (2.4 l, n ¼ 80).…”

“…Phone interviews to obtain demographic information, medical history, lifestyle habits, and water consumption patterns of individuals were conducted (Slotnick et al, 2007). For the purpose of this study, exposure data were obtained from a Food Intake Questionnaire (FIQ) derived from instruments used in previous studies of arsenic exposure in the United States (Karagas et al, 2004;Steinmaus et al, 2005).…”

“…Samples below the detection limit were set to the limit of detection divided by the square root of 2. Additional details on water collection and analysis have been published elsewhere (Slotnick et al, 2007).…”

“…Specific methods on collection, preparation, and analysis of toenail samples in this population have been published previously (Slotnick et al, 2007). Briefly, clipping materials and instructions were mailed to participants after enrollment into the study.…”

“…Inorganic arsenic in different foods was estimated by averaging across the literature (Supplementary Table S2). Comparable methods have been employed (Meacher et al, 2002) and used in our previous reports (Slotnick et al, 2007). Frequency and quantity (serving size) was obtained from the FIQ.…”