Exposure of humans to inorganic arsenic is associated with an increased risk of lung, bladder, skin and other cancers (1,2). Although inorganic arsenic is found throughout the environment, drinking-water constitutes the most significant source of exposure for most populations. Moschandreas et al. have estimated the contribution of drinking-water to the overall daily arsenic exposure to be 35%. Exposure of inorganic arsenic through ingestion (food and water) also depends on certain demographic characteristics, such as age, race/ethnicity, and poverty level (3).
On 22 January 2001, the U.S. Environmental Protection Agency lowered the maximum contaminant level (MCL) allowable for arsenic in drinking-water in the public water systems, from 50 µg/L to 10 µg/L, beginning 23 January 2006 (4). Although this will reduce arsenic exposure of drinking-water from the public water systems that currently do not meet these standards, it will require significant expenditure for modifications to these systems. In addition, exposure at the new standard of the U.S. Environmental Protection Agency may still confer health risks. The costs involved in reduction of arsenic may not be a reasonable option for small municipal water systems or households using personal well-water. Hence, arsenicfree bottled water may be a safe alternative in these settings.
In this study, we compared baseline urinary and toenail arsenic in Ajo and Tucson, Arizona, USA and evaluated the impact of providing arsenic-free bottled water, for one year, on biomarkers of arsenic exposure in Ajo. The primary hypothesis of the study was that provision of bottled-water supplies would reduce arsenic exposure as measured by total inorganic arsenic species in urine and concentrations of arsenic in toenails.
MATERIALS AND METHODS
Study area and selection of households
Census blocks within census tracts were initially selected at random. Based on a probability proportional to size (PPS) sampling protocol (5), our goal was to recruit a maximum of five households per census block. Our inclusion criteria required at least three years of continuous residence in Ajo at the time of recruitment, age over 18 years, exclusive use of tap-water for drinking and food preparation, and no current smoking. Given our restrictive inclusion criteria, we had difficulty in recruiting the sufficient number of subjects using the PPS protocol in Ajo. Subsequently, we resorted to a census of the entire community. In Tucson, the five census tracts that most closely resembled the Ajo population in age distribution (median age= 52 years) and percentage of Hispanic residents (38%) in the 2000 census were selected. Two of the five census tracts were randomly selected, and census blocks and households in these blocks were randomized. Again, we recruited up to five households per block. The majority of households in both the communities that did not meet the inclusion criteria reported extensive use of bottled water. Recruitment of households took place during June-August 2002 in Ajo and during July 2002_August 2003 in Tucson. Up to two eligible subjects from each household were recruited.
At the time of home-visit, participants completed a questionnaire adapted from the National Human Exposure Assessment Survey regarding residential and occupational history, health status, smoking status, and source of water. Water samples were collected using two sterile 50-cc polypropylene conical vials. Cold water from kitchen faucet of participants was allowed to run for one minute before collection began. The water samples were stored at 4 °C until analysis of arsenic.
First-morning void urine samples were collected on the day of appointment for sample collection from each subject. Two sterile 120-cc screw-top containers were provided for the collection of urine. These containers had previously been tested to ensure that they did not impart any measurable arsenic to stored liquid. …