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About the Great Lakes LaMPs study...
Glossary of terms
Other health issues
in the Great Lakes
Apart from the major Great Lakes health concerns of drinking water, recreational water, and fish consumption, there are a number of related issues that are interconnected to air and water quality, pollution and contamination, agriculture and industry, and wildlife.
Air quality |
Bacterial infection and beach closings |
Bacterial contamination and beach closings
Beach closings are restricted largely to shorelines near major metropolitan centers or the mouths of streams and rivers. These closings follow storm events when bacteria-rich surface water runoff is flushed into nearshore areas via streams, rivers, and combined sewer overflows (CSOs). In some instances, beaches may be closed based on the potential for high bacteria levels to develop following storm and rain events. Beaches are also closed for aesthetic reasons, such as the presence of algal blooms, dead fish, or garbage.
Many other sources or conditions can contribute to microbiological contamination, including animal and pet waste that may be deposited onto beaches or washed into storm sewers. Agricultural runoff such as manure is yet another source of contamination. Storm water runoff in rural and wilderness area watersheds can increase densities of fecal streptococci and fecal coliforms as well. Other contaminant sources include the following: infected bathers/swimmers; direct discharges of sewage (from recreational and commercial vessels); and malfunctioning private systems (cottages and resorts).
Human exposure to micro-organisms occurs primarily through ingestion of water, and can also occur via the entry of water through the ears, eyes, nose, broken skin, and through contact with the skin. Gastro-intestinal disorders, respiratory illness and minor skin, eye, ear, nose and throat infections have been associated with microbial contamination of recreational waters. Consequently, one of the specific objectives of the Great Lakes Water Quality Agreement is that "recreational waters should be substantially free from bacteria, fungi, and viruses that may produce enteric disorders or eye, ear, nose, throat and skin infections or other human diseases and infections."
The primary tool used at present to evaluate beach water quality is the measurement of "indicator" organisms that estimate the level of fecal contamination of the water. The indicator organisms most commonly used are fecal coliforms, Escherichia coli (E. coli), and enterococci. These coliform bacteria are microorganisms that usually occur in the intestinal tract of animals, including humans. High levels of these organisms in recreational water are indicative of fecal contamination and the possible presence of intestinal-disease-causing organisms.
Federal and State recreational water quality guidelines recommend bacterial levels below which the risk of human illness is considered to be minimal. For public beaches, the regional Health Departments generally monitor beach water quality. When contaminant indicator levels in the bathing beach water reach levels that are considered to pose a risk to health, public beaches may be posted with a sign warning bathers of these potential health risks.
When reviewing the data, it is important to note that, despite the potential risks to the public from gastrointestinal illness and other infections, water quality monitoring programs vary widely at the state and local levels. Different states and jurisdictions monitor for different indicator organisms, and also have different criteria and standards for postings or advisories. In addition, frequency of monitoring bacterial contamination at public beaches is highly variable around the lake. Because of this variability, it is difficult, and potentially misleading, to compare water quality between jurisdictions or summarize data for all beaches. Even within a beach, variability in the data from year to year may result from the process of monitoring and variations in reporting, and may not be solely attributable to actual increases or decreases in levels of microbial contaminants. It is important to keep these limitations in mind when looking at the recreational water quality data.
The limitations in the ability to compare frequency of exceedances of microbiological guidelines has posed a challenge for the development of a lakewide indicator to evaluate trends in recreational water quality. Despite these limitations, frequency of beach postings to indicate elevated pathogen levels has traditionally been used as an indicator of recreational water quality. Microbial standard exceedances may be a better measure of actual health risk related to recreational water quality, and recent discussions are leaning toward developing an indicator that uses microbial monitoring data, supplemented by beach postings data. This combination will give a much more informative picture about microbial quality of recreational use waters.
Pollution controls and remediation, such as reducing combined sewer overflows, and improvements in sewage treatment, have continued to improve water quality in many areas of the Great Lakes basin in recent years. Long term planning for remediation of microbial contaminants in recreational water needs to include identification of sources of contamination, determination of which sources can be remediated and the costs involved, and timelines for implementation. Although it may not be feasible to eliminate microbial level exceedances completely in recreational waters, it is expected that as sources continue to be remediated, exceedances will continue to decline.
Last modified: April 29, 2003