Long-term moderate exposure to As within a population may lead to adverse health outcomes. Because exposure to As is dependent on a specific population’s lifestyle, location, and/or dietary behavior, we examined a group considered to be moderately exposed, as they consume various foods known to contain As. In conducting this work, we used a multi-faceted approach to determine the extent of exposure to As within the Korean population. Further, the use of hair samples as a viable tool for determining As levels in less extreme exposures was evaluated, and we endeavored to determine the sources of As exposure in the community.
Results indicate that air and water are not significant sources of As exposure. Presently, there is no reference concentration for exposure to inhaled arsenic. The U.S. Environmental Protection Agency (U.S. EPA) has established a quantitative estimate of carcinogenic risk from inhalation that is available in its Integrated Risk Information System (U.S. EPA 2007
). The model uses a linear extrapolation method to calculate risk estimates at various concentrations. For example, the U.S. EPA risk estimate for lifetime exposure to 2 ng As/m3
is one added lung cancer death for every 100,000 individuals exposed. The air As concentrations were intended to aid in controlling for airborne deposition of As onto hair and to determine what percentage of the individual body burden came from inhalation. However, none of the participants had measurable in-home indoor air As levels in excess of 2 ng As/m3
, with only one location slightly exceeding this air As concentration (control; bedroom of a 12-year-old). Drinking water As values were analyzed to determine if As was a significant source of exposure and to more accurately determine hair As levels by controlling for arsenic deposition on hair from washing and bathing. Consuming drinking water at a rate of 1.5 L/day will not appreciably increase the As level in urine in this population. The percentage of inorganic As contributed by this source is small and similar to that obtained from clam consumption.
Although the analysis of shellfish (mollusks) indicate that total As is present, only a small fraction is inorganic As. Clam species inorganic As concentrations were all less than 10% of the total As levels, with the highest being 8.5% and with many species having only 2–3% inorganic As. This suggests that these shellfish are not a large source of inorganic As in this population. This outcome does not change in spite of recent findings by Ostrom and coworkers (2007)
. They observed total As levels in geoduck to be greater than those observed in horse clams for this study, but found no detectable inorganic As levels in the geoduck samples analyzed. The supposition that shellfish is not a large source of inorganic As is further supported by intake estimates. Although this population consumes (≈ 25 g/day) more than the general population (10–18 g/day), the average inorganic As intake from the shellfish was low (0.5–0.7 μg/day) [Office of Environmental Health Hazard Assessment (OEHHA) 2001
Compared with the various studies investigating background levels of the sum of As species in urine, the Korean participants who provided urine samples for this study had an average value (≈30 μg/L) higher than that observed in European countries and in the United States (≤ 10 μg/L) but below that observed in Japan (≈50 μg/L) (Buchet et al. 1996
; Foà et al. 1984
; Gottlieb et al. 1993
; Kalman et al. 1990
; Kavanagh et al. 1998
; Kristiansen et al. 1997
; Pollisar et al. 1990
; Trepka et al. 1996
; Vahter et al. 1995
; Yamauchi et al. 1989
). U.S. population data from NHANES indicate that the 50th percentile for sum of species in urine was 6.0 μg/L (although the estimate may be slightly biased), and the 95th percentile was 18.9 μg/L (Caldwell et al. 2008
). The 50th percentile value determined from our study is greater than 3-fold the 50th percentile seen nationally and exceeds the 95th percentile level. The 95th percentile sum of species value is significant within the NHANES distribution, as the remaining 5% represents many individuals. Although the sample size of 67 individuals who provided urine samples is too small to represent the whole of the Korean community, our results suggest that this population may be contained within the remaining 5th percentile of the NHANES distribution representing the U.S. population. Also, based on urinary As (inorganic and sum of species) results, this community may have a percentage (6%) of individuals with elevated inorganic As exposure due to dietary behavior.
The Korean community consumes food-stuffs on a daily basis that contain As, such as rice, seaweed, and shellfish. Chicken may also be of concern in some populations, but the consumption rate in this community (21 g/day) is but a third of the average daily intake observed nationally in the United States (60 g/day) (Lasky et al. 2004
). The consumption rates for foodstuffs () led to an estimated total As intake approximately equal to the estimated urine total As excretion rate. Although urinary excretion of As ingested is not complete and may underestimate the total amount ingested because of a portion of the As body burden being contained in and excreted via hair and skin, the mass balance results suggest that these food items will represent the primary sources of exposure for total As and accordingly, for inorganic As. It should be noted that some of the data used to calculate mass balance were from studies with small sample size, unknown species type, and different methodologies (e.g., raw vs. cooked, dry weight vs. wet weight), and these variables could not always be controlled for in this study. Accordingly, the choice of studies selected for determining the median total As value and/or the possibility that we did not obtain all the literature values could facilitate an alteration in the total As intake.
In this population, the average fraction of the total As in urine comprising the sum of As species is 25%, or 48 μg/day (). Of this 48 μg/day, the shellfish As data obtained for the study indicate that only a small fraction (approximately 4%; 2 μg/day) comes from the consumption of shellfish (mollusks). Exposure to inorganic As, DMA, and MMA from finfish, crab, shrimp, and seaweed was not addressed in this study, as the available data are insufficiently robust to allow for an approximation. These sources, along with others discussed (drinking water, rice, clams, and to a lesser extent, chicken), should represent the vast majority of the As intake that is excreted in urine as the sum of As species. A rough calculation based on intake values used or derived in this study indicates that drinking water could account for 3 μg/day of inorganic As (2 μg/L × 1.5 L/day), and rice for approximately 16 μg/day of inorganic As (160 g/day × 0.1 μg/g). Chicken could possibly contribute 2 μg/day inorganic As (21 g/day × 0.1 μg/g), and shellfish (mollusks) about 2 μg/day as sum of As species. The sum of these intakes would represent approximately half of the total sum of As species intake of 48 μg/day, based on urinary As levels. The remaining half may come from crab, shrimp, finfish, seaweed, and possibly other unidentified sources, or the values used in this calculation may underestimate actual intake levels.