Urinary Arsenic Levels in Hernando County, FL Residents with Private Wells

BACKGROUND:  Inorganic arsenic is a carcinogen when consumed over many years, and is the kind of arsenic that is associated with well water. Private wells in many central Florida counties have been found to contain levels of arsenic > 10 μg/L, which is the Maximum Contaminant Level (MCL) established by the U.S. Environmental Protection Agency. The Florida Department of Health (FDOH) conducts targeted private well testing in areas of concern. In 2013, FDOH conducted a biomonitoring study in Hernando County, where nearly 400 wells out of 1,200 tested have been found to have elevated arsenic levels. The purpose of this study was to test whether individuals living in homes with arsenic levels above the MCL who use bottled water or have a point of use (POU) filter on their main source of water in the house (e.g. kitchen sink) are ingesting unsafe levels of arsenic through other unfiltered tap water in the home. 

METHODS:  From April through July of 2013, 360 participants from 166 households participated in the study (overall response rate 29.5%). Nearly 50% of the participants were from “control” households with well water arsenic levels below 8 μg/L, while the other half were classified as “case” households with arsenic levels exceeding 10 μg/L. Participants provided urine and water samples to test for arsenic and completed a questionnaire on water consumption and exposure patterns, dietary history, and other possible sources of arsenic exposures. Water and urine samples were sent to the FDOH laboratory for analysis of total arsenic, and urine samples were also analyzed for creatinine and speciated arsenic levels for samples > 30 μg/L. 

RESULTS:  Creatinine corrected, urinary total arsenic levels were similar for cases using POU filters or bottled water and controls (geometric means of 7.17 and 7.19, respectively). No children in this study were found to have elevated levels of inorganic arsenic. The majority of case households reported bottled water as their most common source of drinking water (59.8%), and 47.5% reported using bottled water for cooking. However, the majority of case households reported using unfiltered well water to brush their teeth (88.7%).

CONCLUSIONS:  The current practice employed by the Florida Safe Water Restoration Program of supplying POU filters or bottled water to households with arsenic levels in private wells between 10 μg/L and 50 μg/L appears to be sufficiently protective in eliminating increased risk to residents of arsenic exposure through tap water