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Roundtable on Environmental Health Sciences, Research, and Medicine; Board on Population Health and Public Health Practice; Institute of Medicine. Understanding the Connections Between Coastal Waters and Ocean Ecosystem Services and Human Health: Workshop Summary. Washington (DC): National Academies Press (US); 2014 Jun 2.

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Understanding the Connections Between Coastal Waters and Ocean Ecosystem Services and Human Health: Workshop Summary.

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7Ensuring Benefits of Recreational Waters Through Monitoring

This chapter focuses on one of the ecosystem services provided by natural water—recreational opportunities. Systematic monitoring of recreational waters is key to ensuring that people can benefit from this ecosystem service. A summary of some of the challenges of water quality monitoring is presented and is followed by a summary of the discussion that ensued.


Edward Laws, Ph.D., Professor.

Louisiana State University School of the Coast and Environment

Edward Laws began his presentation by highlighting that the monitoring of recreational waters for the purpose of deciding safe use for the public is unfortunately in a very imperfect state of affairs. Generally, monitoring of recreational waters is a responsibility of local health departments, although the U.S. Environmental Protection Agency (EPA) is charged with setting up standards, confirming test results, and facilitating labs and technology for localities. Laws noted that there are a number of issues surrounding recreational use of natural waters, some of which are close to being resolved and others that remain unclear, which will be presented in his talk.

Valuing Recreational Waters

Laws discussed a paper by Costanza and colleagues (1997) in which the value of ecosystem services, including recreational waters, was ranked and illustrated according to natural capital. The authors described the intrinsic connections between human activities and the environment and argued that there is a benefit to human welfare added to the market values of these services (Costanza et al., 1997). Laws highlighted a list of ecosystem services and the value, in billions of dollars per year, given in the analysis (see Box 7-1). Nutrient cycling was perceived as the biggest ecosystem service provided, and farther down the list recreation was found in ninth place, worth $815 billion per year. It is interesting to note that most of these ecosystem services are aquatic.

Box Icon

BOX 7-1

Value of Ecosystem Services (billions of dollars per year). SOURCE: Costanza et al., 1997.

Laws noted that Kamehameha Schools in Hawaii initiated a program for students as part of the Center for Ocean and Human Health at the University of Hawaii. The program is for children of Hawaiian ancestry and has played a role in motivating students in the conservation of recreational waters and preservation of their cultural practices. In this example, the value placed on recreational waters in Hawaii was leveraged to support education and conservation.

Monitoring of Recreational Waters

In 1972, the EPA began to address the monitoring of pathogens in recreational waters. Laws highlighted that at the time there was remarkably little information on which to base water quality criteria. There were some studies on concentrations of fecal coliform bacteria and sampling for salmonella. The results of those studies indicated that if the samples contained between 1 and 200 fecal coliforms per hundred milliliters, then 32 percent of the samples likely contained salmonella. As the number of fecal coliform counts increased, the percentage of the water samples that contained salmonella also increased; for instance, more than 2,000 fecal coliform measured per hundred milliliters indicated that 97.6 percent of the water samples likely contained salmonella.

Laws noted that the EPA then organized epidemiological studies to improve the quality of evidence. For the studies, the EPA needed to find recreational waters in the United States that were contaminated with fecal pollution and where people were utilizing the waters for swimming. The EPA identified both marine water and freshwater that were assayed for a list of indicator organisms that would be associated with human feces and then correlated those data with the incidence of people getting sick from going in the waters (defined as submerging one's head under water). Laws highlighted that with these EPA studies the number of times the person went under water or the amount of water the person swallowed did not make a difference; it was all counted the same. In comparison, if the studies were conducted in the United Kingdom, the amount of time a person was in the water and activities they participated in would have been assessed. Roughly 7 to 10 days after people were identified as going in the water the EPA would follow up with these individuals and ask if they had gotten sick. Reported illnesses associated with ingesting pathogens related to feces were recorded as highly credible gastrointestinal illnesses and were correlated with the previously assessed indicator organisms.

Laws explained that Enterococcus and Escherichia coli (E. coli) bacteria are found in everyone's gastrointestinal system and are shed with fecal matter (regardless of whether people are healthy or sick); as such, if feces were present in the water, one would expect to find these bacteria. Figure 7-1 shows the statistical regressions that were developed for marine water in which the correlation for Enterococcus is statistically significant but the correlation for E. coli is not and is much more scattered. The statistical regressions for freshwater are not displayed, but Laws noted that both Enterococcus and E. coli correlations were statistically significant in freshwater samples.

FIGURE 7-1. Marine water correlation between highly credible gastrointestinal illness in swimmers and bacterial concentrations.


Marine water correlation between highly credible gastrointestinal illness in swimmers and bacterial concentrations. NOTE The y axis represents the occurrence of highly credible gastrointestinal illness per 1,000 swimmers and the x axis represents the (more...)

The EPA released this marine and freshwater criterion for fecal matter bacterium in the Quality Criteria for Water 1986 report, also known as the gold book. Based on the report, the geometric mean and single sample assay for Enterococcus in marine waters is not to exceed 35 per 100 mL and 104 per 100 mL, respectively (EPA, 1986). For freshwaters, the geometric mean and single sample assay for E. coli is not to exceed 126 and 235 per 100 mL, respectively, and Enterococcus is not to exceed 33 and 61 per 100 mL, respectively (EPA, 1986).

Limitations with Current Water Quality Criteria

Laws noted that there are several problems with the water quality criteria and sampling. First, the organisms that are being sampled are indicator bacteria and are not responsible for causing the health problems. Scientists rely on the fecal indicator bacteria because these are more abundant in feces than the actual pathogens and require smaller samples to detect their presence. Detection of the bacteria, viruses, protozoa, and worms that lead to gastrointestinal illnesses is much more difficult. Laws explained that 70 percent of hospitalizations from gastroenteritis in the United States remain due to unknown causes, especially because it can be quite expensive to assay for all the possible pathogens.

A second limitation is that traditional sampling tests take approximately 24 hours to obtain results because the cultures require approximately 24 hours to grow on the specified medium. For example, Boehm (2007) examined the correlation between one day's samples and the next day's samples at recreational beaches and found no correlation between the Enterococcus counts of consecutive samples. Laws noted that because of the time delays in testing, the results can indicate if it is safe to go in the water yesterday but give no indication of whether the water is safe today. In another study from Boehm and Weisberg (2005), the authors found that because of the 24-hour delay in assessing Enterococcus counts that beaches were often closed when the counts were acceptable. The closures followed days where the beaches were open and Enterococcus counts exceed 104 per 100 mL (Boehm and Weisberg, 2005). Additionally, Boehm (2007) has shown that there is extreme variability even between samples obtained every minute during 1-hour intervals, which raises questions about the adequacy of these water quality sampling tests.

Third, Laws noted that the assumption is that the fecal indicator bacteria come from human feces and at a specific time, but in reality there are multiple potential sources in the natural environment, including other mammals, birds, fish, and runoff from beach sands, soils, and plants (Muller et al., 2001; Yamahara et al., 2007). Some of these environmental reservoirs are not associated with feces or human pathogens at all, as seen with soils in Hawaii that have natural colonies of Enterococcus (Oshiro and Fujioka, 1995). In another study (Johnson et al., 2012) the authors examined two types of Vibrio bacteria (V. parahaemolyticus and V. vulnificus) found in recreational waters and which can cause gastrointestinal problems. The authors looked at concentrations of these bacteria in oysters and correlated this with the temperature and salinity of the oysters. Laws explained that 70 percent of the variance in the data could be explained based on the temperature and salinity of the oysters, which resulted in a strong correlation between the observed and predicted concentrations of the Vibrio bacteria in the oysters.

Failures of the Recreational Waters Monitoring System

Laws included two examples in his presentation, which describe important factors where the system failed when monitoring recreational waters in the United States and other countries. The first example is from Delhi, India, in 1955–1956. The public water supply became contaminated with sewage during the monsoon floods (Laws, 2000). The authorities ramped up the filtration and chlorination and assayed the treated water by looking for fecal indicator organisms. In this case, the water met the criterion for E. coli under indicated standards but approximately 20,000 clinical cases of hepatitis A were reported. Laws highlighted that viruses in general are more resistant to chlorine than bacteria, and in this example, infectious hepatitis or hepatitis A virus was particularly resistant. Because the treatment was targeted for E. coli, which is highly susceptible to chlorine, the authorities did not consider assessing for other pathogens that might have been present.

In 1993 in Milwaukee, approximately 400,000 people became ill after Cryptosporidium parvum (C. parvum) contaminated the public water supply. C. parvum is a protozoan that is a common waterborne pathogen. Chlorine is not an effective treatment mechanism because the C. parvum forms eggs that are resistant to chlorine (Corso et al., 2003), and water filtration is the only effective solution. Laws noted that this is another example where reliance on fecal indicator bacteria can be misleading about the water quality, and many people can become sick.

Laws explained that the EPA is working on two major factors to improve monitoring of recreational waters. The first involves finding a way to reduce the time between collecting the sample and obtaining the results. As noted above, the 24-hour assays have many limitations and do not provide all the necessary information. Real-time quantitative polymerase chain reaction (qPCR) has proven effective by detecting the DNA from the organism. However, the presence of DNA does not mean that the organism is present, which increases the possibility for false positives. For the EPA to consider utilizing this new assay, the determination must be supported by epidemiological studies that relate the assay results to human health risks.

Bacteriodes are the second factor in which the EPA is focusing its efforts. Bacteriodes are human-specific anaerobic bacteria and are a large component of human feces (they are present at higher concentrations than the coliforms that are currently used in sampling). Because they tend to be host specific, they can provide a clear target for DNA analysis and clear indication that the water was contaminated with human feces. Whereas they do not survive long in the environment, the viruses (bacteriophages) that infect the bacteriodes do persist for longer periods (e.g., weeks) and the assays are actually for the viruses, not the bacteriodes. Laws stated that this is the kind of indicator that is needed because it is present at constant levels through a period of time in the environment, it can survive sewage treatment, and it is a better indication of the presence of human enteric viruses that cause gastroenteritis.

In closing, Laws provided a summary of the problems identified in his presentation surrounding the monitoring of recreational waters that could be the focus of future efforts:

  • address temporal and spatial variability (possibly develop new models),
  • resolve nonspecificity of indicators (bacteroides are promising),
  • find assays that mimic survival of the hardiest pathogens (bacteriophages may provide a better assay),
  • need rapid results (qPCR is promising),
  • address the fact that some human pathogens are unrelated to human feces, and
  • relate new indicators to human health risks (requires epidemiological studies, which are expensive).


Bernie Goldstein from the University of Pittsburgh asked Laws to comment on the implications of the variability in beach monitoring data, noting that the third highest count of Enterococcus occurred on a day the beach was closed because it followed a day with a count exceeding the 104 per 100 mL limit. He continued to ask if the 104 count per 100 mL standard provides any indication of whether the bacteria level on the following day will exceed the established background level. Laws noted that typically these beach environments have a longshore current system so that what was present today will be downcurrent tomorrow, unless there is a continuous point source that is leaking into the water. So the nature of the input would determine the water quality on the following day for the recreational water.


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Copyright 2014 by the National Academy of Sciences. All rights reserved.
Bookshelf ID: NBK209263


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