By Melissa Murray Jordan, senior environmental epidemiologist, Bureau of Epidemiology, Division of Disease Control and Health Protection, Florida Department of Health
Private wells in many central Florida counties have been found to contain levels of arsenic above the federal maximum containment level (MCL) of 10 μg/L (micrograms per liter). Knowing it is present is important to the public’s health; but how serious is this? Even exposure to low amounts of arsenic can potentially lead to an abnormal heart rhythm, damage to blood vessels, and a tingling sensation in hands and feet. Inorganic arsenic, the type in this water, is a carcinogen when consumed over many years. High levels of exposure to arsenic may lead to death. To address this known contamination, the Florida Safe Water Restoration Program provided filters or bottled water to households with arsenic levels in private wells between 10 μg/L and 50 μg/L. In partnership with the Florida Department of Environmental Protection, the Florida Department of Health (FDOH) decided to test the effectiveness of this program as well as explore any further impact of the contaminated water on residents living in areas of concern.
The study targeted Hernando County where nearly 400 of the 1,200 wells tested had elevated arsenic levels. This time, scientists wanted to understand if residents who weren’t drinking unfiltered well water (people who were drinking bottled water or using a filter in their homes) were still ingesting unsafe levels of arsenic through other unfiltered tap water in the home. It is widely known that arsenic exposure often occurs from drinking water, but what about exposure to water in other ways? What about brushing your teeth with unfiltered water? Or when cooking with unfiltered water?
A critical initial step of this project was forming a workgroup with representatives from many disciplines to inform various steps of the study:
- Environmental specialists to provide background information on areas of known arsenic contamination in the state and details on the private well testing database;
- Epidemiologists to provide guidance on the study design and sample size;
- Laboratorians for developing the protocol for collecting, shipping and testing the water and urine samples;
- Toxicologists to interpret the risk of arsenic exposure;
- And communications experts to develop press releases, frequently asked questions and coordinate media.
Funding from CDC’s Environmental Public Health Tracking program allowed the state to engage these experts and ensured a high-quality study.
From April through July of 2013, 360 individuals from 166 households participated in the study. Nearly 50% of the participants were from control households: households with well water arsenic levels below 8 μg/L (below MCL). The other half were classified as case households: households with arsenic levels exceeding 10 μg/L (at or above the MCL). Participants provided urine and water samples, and completed a questionnaire on water consumption, dietary history and other possible sources of arsenic exposures. Water and urine samples were sent to the public health laboratory in Jacksonville, Florida for analysis of total arsenic.
The majority of case households (59.8%) reported bottled water as their most common source of drinking water, 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%).
In many biomonitoring studies, only adults participate. This study also included children. Simply because of their size, a small amount of a chemical can have a larger impact in a child than the same amount in an adult. Scientists felt it was valuable to look at a range of people without omitting the smallest members of the community. Additionally, children tend to have different behaviors from the adults in their homes. For example, they may take baths rather than showers – and kids may be more likely to ingest that bath water. Fortunately, no children in this study were found to have elevated levels of inorganic arsenic.
Results: Residents using filtered or bottled water for drinking were not at an increased risk for arsenic exposure through other unfiltered household water sources.
The distribution of filters and bottled water was helping to prevent residents from exposure to arsenic. While testing for contaminants in the wells was an important first step to understanding the problem, biomonitoring provided a more complete picture of the full impact on a population. This was obviously good news to the residents and researchers alike.