Human Health Effects from Exposure to Marine Recreational Waters

Wendy S Quirino*, Lora E. Fleming, MD, PhD, MPH, MSc**, Helena Solo Gabriele Phd+, Dominick Squicciarini MPH**, Margia A Arguello*.

*Dept of Biology; **NIEHS Marine & Freshwater Biomedical Sciences Center at the Rosenstiel School of Marine and Atmospheric Science; +Department of Civil Engineering, University of Miami, Miami, FLThis study was funded in part through the National Institute of Environmental Health Sciences (NIEHS), the Miami Dade Dept of Health, and NIH Minority Undergraduate Training Grant

INTRODUCTIONMicrobial water quality indicators are used to determine whether a water body is safe for recreational purposes. The

microbial indicators used are found in high concentrations in sewage. Therefore, if high concentrations of the microbial indicators are found in a water body, then there is reason to suspect that the area is impacted by sewage and thus not safe for swimming. Recently there have been concerns raised about the appropriate use of microbial indicators to regulate recreational uses of water bodies, in particular water bodies located in tropical and sub-tropical environments. Some of the concerns include the potential for the indicators recommended by the USEPA to multiply (or regrow) in the environment, thereby resulting in artificially elevated concentrations above that observed from sewage impacts alone and the lack of water quality and epidemiologic study within tropical and sub-tropical regions which is where regrowth of the microbial indicators is suspected to occur.

The purpose of this analysis was to preliminarily assess whether microbial indicators are useful tools for establishing recreational standards within sub-tropical environments for areas where there is no known discharge of sewage. Specifically, this project evaluated the relationship between microbial water quality indicators and public health. Three water quality indicators were utilized for this evaluation: enterococci, fecal coliforms, and Clostridium perfringens. The relationship between public health and microbial indicators was evaluated through this investigation within 2 beaches in Miami-Dade County. One beach had been characterized by elevated concentrations of microbial indicators relative to that observed at the second beach. Neither beach received sewage discharges from a known source. Water samples were collected daily at each beach during a wet and dry season month. An epidemiological questionnaire previously used in a large study of Los Angeles recreational beach goers was adapted to assess the swimming related symptoms and exposure as a prospective cohort study. The data were evaluated for differences in self reported symptoms between the 2 beaches and between the dry and wet months, as well as other analyses.

From the epidemiological point of view, issues of relatively small sample size of the participant population, as well possible participant selection bias and exposure assessment, limit the analysis of these Pilot study data. the final study population consisted of 63 families with 208 (86%) individuals (3.3 individuals/family); 75 (36%) were interviewed during the dry month and 99 (46%) at Hobie Beach. In all, 35 (17%) of the subject population reported at least 1 symptom occurring since their visit to the beach, with cough (7%) and skin rash (5%) being the most frequently reported symptoms. In general, there was no significant association between the number or type of reported symptoms, and the different sampling months or beach sites, although persons who returned repeatedly to the beach (“Over exposed”) were more likely to report symptoms. Overall, the number of indicator organisms correlated negatively with the frequency of symptoms reported by recreational beach goers, possibly due to the lack of individual exposure information. Larger epidemiologic studies are recommended to further evaluate these associations.

MethodsThe pilot study was a prospective cohort study. It consisted of 2 months of daily monitoring

for recreational water quality using multiple bacteriologic indicators, with 2 retrospective surveys of reported symptoms from exposed beach users at 2 beach locations performed on various days during the 2 study months. The 2 beaches were monitored daily during 1 dry season month (April) and 1 wet season month (July) because historic data indicated that the wet season might be associated with higher levels of indicator organisms. Both beaches are used heavily for all types of water sports throughout the year by Miami natives and tourists.

After obtaining approval from the Human Subjects Committee (IRB) of the University of Miami (00/716B) and the Miami Dade County Health Dept IRB, the Investigators enrolled residents of Miami Dade County at the 2 beaches who immersed their face in the beach water during the interview days. Tourists and non residents were considered ineligible due to logistical follow up issues. Any person who immersed their face in the beach water on the date of enrollment, had not been at the beach in the prior 7 days, and agreed to the telephone follow up in Spanish or English was eligible to participate. Parents were interviewed about symptoms for exposed children age 17 and younger. Logistically, 1 adult was identified to interview for each family although symptoms were collected for all members of the participating family.

After reviewing and signing the Informed Consent (one per family), brief demographic and contact information were collected at the Beach. Then, as per the 1995 Santa Monica Bay Study (Haile et al. 1999) and per expected incubation periods for enteric diseases, the participants were contacted by phone 8 to 10 days from exposure to ascertain symptoms, particularly gastrointestinal symptoms, since the visit to the beach as well as any additional beach exposures.

The data were entered into an Excel 2000 database. The Data were exported and analyzed in SPSSVersion 10. Dichotomous variables were analyzed using chi squared and ttest/Fishers Exact Test analysis, while continuous variables were analyzed using ttest. Correlations between reported symptom frequency and indicator organisms levels on interview days were performed using Pearson’s correlation. The alpha level of 0.05 was used for all tests of significance using 1 tailed tests, however given the small sample size and Pilot nature of the data, testing based on multiple comparisons was not used.Sewage Pipe Break

Of note, there was a sewage pipe break at the beginning of the Dry Month on the Miami River; both study site beaches had Beach Advisories with markedly reduced use for several days during this time. The beaches had re opened with the appropriate regulatory levels of indicator microbes ascertained for over a week before beginning the study interviewing.

ResultsThe pilot study consisted of 2 months of daily monitoring for recreational water quality using

multiple bacteriologic indicators, with a prospective cohort survey of reported symptoms from exposed beach users at 2 beach locations performed on 5 days during the 2 study months.

With regards to the Study Hypotheses relevant to the epidemiologic evaluation, the following results were found. There was a significant correlation between organism density and reported human symptoms (Specific Aim III Hypothesis 2), however the correlation was negative: persons were significantly more likely to report symptoms when the average microbial indicator counts were decreased. Clostridium was significantly but negatively associated (Pearsons Correlation=0.88 (p=0.03)) (Specific Aim V Hypothesis 1). In part this may be due to the lack of individual exposure assessment; there were 2 samples taken each day in 2 different locations at each beach, but no individual participant measures. It may also reflect a “family effect” to the extent that families share communicable infectious diseases, particularly those with young children.

There were not significantly higher symptoms reported for the Hobie Beach participants compared to the Crandon Beach participants (Specific Aim III Hypothesis 3). Of note, skin rashes were more likely to be reported from Hobie Beach (8 (4%)) than Crandon Beach (3 (1%)), although not significantly. Staph aureus and other microbes more often associated with skin infections were not measured although skin symptoms have been associated with microbial indicators in other studies (Prieto 2001). Participants were slightly more likely to report at least 1 symptom at Hobie beach (18%) compared to Crandon beach (15%) but not statistically significant. It is possible that the small sample size was unable to detect a statistically significant difference between these 2 exposure groups.

Participants were more likely to report at least 1 symptom during the wet (18%) compared to the dry month (15%), but not significantly. There were no significant differences between the reported symptoms for the dry and wet month participants (Specific Aim IV Hypothesis 2), although there was a trend for more symptoms to be reported in the wet than the dry month as originally postulated. It is possible that the small sample size was unable to detect a statistically significant difference between these 2 exposure groups.

Those who returned to the beach between study enrollment and follow up, considered possibly “over exposed,” were significantly more likely to report a cough with phlegm (p=0.05), but not to have a cough (p=0.57) nor any other symptom. In general, more symptoms were reported by those who were “over exposed” (22%) than those who did not return to the beach (16%), although not significantly, suggesting a possible dose response relationship.

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ConclusionsThere were significant limitations to this study. The most important limitation was the

relatively small number of participants and the few days of epidemiologic data collection . As well as affecting the correlation analysis, this made it difficult to distinguish background health effects from a true increase associated with beach water exposure. There was also no individual exposure information but rather “ecological” exposure measures by beach location; this may have under or over estimated the microbial exposure of the individual participants. There was also no establishment of baseline symptoms prior to exposure; thus, recall bias based on reporting of retrospective symptoms was possible. The use of residents (rather than tourists) for logistic reasons may have selected for a more “resistant” population less likely to experience health effects. Finally there was no definitive unexposed control group, although analyses of those who did not get their faces wet did not indicate any difference in reported health effects.

Therefore, the epidemiologic portion of this Pilot Study did not support a strong hypothesized difference between either the 2 study site beaches (Hobie vs Crandon) or the 2 study months (wet vs dry). There was some indication that persons with multiple exposures to beaches may be at greater risk for reporting symptoms, suggesting a possible dose response relationship. Finally, there was an inverse relationship between the number of reported symptoms and the microbial indicators, probably due to lack of individual exposure assessment.

RecommendationsFuture epidemiologic studies should include a larger number of participants distributed

over a greater number of sampling days. Broadening of the microbial indicators to include skin pathogens and increased skin exposure assessment may be warranted. In particular, individual exposure assessment and the establishment of symptoms prior to exposure would strengthen future studies scientifically.