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© 2004 American Public Health Association
RESEARCH AND PRACTICE |
Ryan H. Dwight and Betty H. Olson are with the Environmental Health Science and Policy Program, Department of Environmental Health, Science, and Policy, University of California, Irvine. Dean B. Baker is with the Department of Medicine and Center for Occupational and Environmental Health, University of California, Irvine. Jan C. Semenza is with the School of Community Health, Portland State University, Portland, Ore.
Correspondence: Requests for reprints should be sent to Dean B. Baker, MD, MPH, UC Irvine Center for Occupational and Environmental Health, 5201 California Ave, Suite 100, Irvine, CA 92612 (e-mail: dbaker{at}uci.edu).
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMETHODSRESULTSDISCUSSIONReferences |
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We compared rates of reported health symptoms among surfers in urban North Orange County (NOC) and rural Santa Cruz County (SCC), California, during 2 winters (1998 and 1999) to determine whether symptoms were associated with exposure to urban runoff. NOC participants reported almost twice as many symptoms as SCC participants during the 1998 winter. In both study years, risk increased across symptom categories by an average of 10% for each 2.5 hours of weekly water exposure. Our findings suggest that discharging untreated urban runoff onto public beaches can pose health risks.
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONReferences |
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Coastal waters along public beaches can be polluted by urban runoff, which is water that carries non–point-source pollution via surface waterways to the ocean.1 A variety of illnesses have been associated with exposure to polluted recreational coastal waters.2–4 In this study, which involved 2 geographic watersheds differing in terms of urbanization, we measured reported health effects on individuals with high levels of exposure to coastal waters.
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METHODS |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONReferences |
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North Orange County (NOC), California, was the "urban" site because its watershed is 1 of the most developed areas in the world and generates highly polluted runoff waters.5–9 We selected Santa Cruz County (SCC), California, as the comparison "rural" site because of its coastal water quality indicators (Figure 1
) and watershed characteristics.
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We conducted 2 cross-sectional surveys of surfers from NOC and SCC, 1 in April 1998 and 1 in April 1999, and gathered data on reported health symptoms (e.g., vomiting, diarrhea, sore throat) experienced during the previous 3 months. The 1998 El Niño winter had led to record high precipitation throughout California, while the 1999 La Niña winter had led to record low precipitation in NOC. NOC had lower total rainfall than SCC in both years, yet the former had higher coastal water coliform (a water quality measure of pollution) levels (Figure 1
). Surfers were selected as the study population because of their regular exposure to coastal waters. Interviewers at surfing beaches recruited participants by approaching all individuals who had wetsuits and surfboards. Those who reported surfing at least once a week and were 18 years or older were eligible to be interviewed. Demographic information was collected, as well as information on symptoms experienced during the previous 3-month period. Participants also reported the amount of time they were exposed to coastal waters.
Multiple reports of 1 symptom were combined, allowing only 1 symptom report per participant, equivalent to a 3-month period prevalence. Logistic regression analysis was used to estimate adjusted odds ratios (ORs) comparing symptom reporting rates between the 2 counties, stratified by year. The final logistic model included the following variables: county, water exposure, gender, age, occupation, educational level, annual income, political outlook, and level of concern about water quality. The latter 2 variables were included to control for potential reporting bias associated with perspectives about the potential health effects of environmental pollution and water quality.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONReferences |
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In 1998, investigators interviewed 479 participants in NOC and 374 in SCC. In 1999, investigators interviewed 662 participants in NOC and 358 in SCC. At each site, response rates were above 80% in both 1998 and 1999. The mean age of the participants was 30 years, and 93% were male.
The urban versus rural analysis showed that NOC participants reported almost twice as many symptoms overall as SCC participants (OR = 1.85; 95% confidence interval [CI] = 1.4, 2.5) during the 1998 El Niño winter (Table 1). In that year, NOC participants reported higher rates of every symptom. During the 1999 La Niña winter, NOC participants reported only slightly more symptoms than SCC participants (OR = 1.17; 95% CI = 0.9, 1.6) and reported slightly higher frequencies in regard to 6 of the 12 symptoms. Odds ratios decreased consistently across all symptoms between the 2 winters. In both study years, risk increased across almost every symptom category by an average of about 10% (OR = 1.1) for each additional 2.5 hours of water exposure per week.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONReferences |
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Results from this investigation and other studies9,10 suggest that discharging untreated urban runoff onto public beaches can pose health risks. This conclusion is supported by the higher reporting rates of symptoms among urban NOC participants during the rainy 1998 El Niño winter, after controling for possible confounding (due to demographic characteristics) and reporting bias (due to concern about coastal water quality). The exposure–response relationship demonstrated for most of the symptoms further supports this conclusion. Direct associations have been reported between pollution levels in runoff waters and urban land use, population levels, and amount of impervious surface area in the watershed.11–15
Research on the health consequences of urban runoff represents a relatively new area of investigation, despite decades of urban runoff contaminating coastal waters.7,12 Most previous epidemiological studies focused on waters contaminated with domestic sewage, and the majority found associations between water pollution levels and incidence levels of symptoms.2–4,16–21 Most epidemiological studies of recreational water use have focused on single exposure events rather than exposure over time.2,3 Our study assessed 3-month prevalence rates of symptoms and demonstrated that average symptom prevalence was associated with different levels of water pollution.
To reduce the potential for confounding, we sampled from the same source population during both years and used comparable groups of surfers with relatively similar social characteristics. The high participation rates (above 80%) lowered potential bias due to selective participation. The study was cross sectional, which represents a limitation in terms of assessment of symptoms over a 3-month period, but any recall bias was likely to be nondifferential and toward the null. To reduce potential differential reporting bias, we adjusted for participants’ level of concern about coastal water quality. Another limitation is that we did not measure water quality at the sites, so we were unable to determine the specific nature of the pollutants associated with symptoms.
In summary, this study suggests that discharging untreated urban runoff onto public beaches can pose health risks. These potential health risks warrant greater public health surveillance, as well as greater efforts to reduce pollutants discharged onto public beaches. Large-scale prospective investigations are needed to further characterize the health risks of people exposed to untreated urban runoff in coastal waters.
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Acknowledgments |
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We are grateful to Dr Harvey Molotch, former director of the Ocean and Coastal Policy Center at the University of California, Santa Barbara, and the University of California Toxic Substances Research and Teaching Program for their early financial support. We also thank Dr JoAnne Prause, Dr Dele Ogunseitan, the interviewers, and all of the participants for taking part.
Human Participant Protection
The use of human participants in this study was approved by the institutional review board of the University of California at Irvine. The participants provided verbal informed consent.
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Footnotes |
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Contributors
All authors contributed to the design, writing, and final approval of the article.
Accepted for publication April 25, 2003.
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References |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONReferences |
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1. Field R, O’Shea M, Brown MP. The detection and disinfection of pathogens in storm-generated flows. Water Sci Technol. 1993;28:311–315.
2. Saliba LJ, Helmer R. Health risks associated with pollution of coastal bathing waters. World Health Stat Q. 1990;43:177–184.[Medline]
3. Pruss A. Review of epidemiological studies on health effects from exposure to recreational water. Int J Epidemiol. 1998;27:1–9.
4. Cabelli VJ. Swimming-associated Illness and recreational water quality criteria. Water Sci Technol. 1989;21:13–21.
5. Bay SM, Greenstein DJ. Toxicity of dry weather flow from the Santa Monica Bay watershed. Bull South Calif Acad Sci. 1996;95:33–45.
6. Gold M, Bartlett M, Dorsey J, McGee C. Storm Drains as a Source of Surf Zone Bacterial Indicators and Human Enteric Viruses to Santa Monica Bay. Santa Monica, Calif: Santa Monica Bay Restoration Project; 1991.
7. Cross J, Schiff K, Schafer H. Surface runoff to the Southern California Bight. In: Annual Report. Long Beach, Calif: Southern California Coastal Water Research Project; 1992:19–28.
8. Schafer H, Gossett R. Storm Runoff in Los Angeles and Ventura Counties. Long Beach, Calif: Southern California Coastal Water Research Project; 1988. Final report.
9. Dwight RH, Semenza JC, Baker DB, Olson BH. Association of urban runoff with coastal water quality in Orange County, California. Water Environment Res. 2002;74:82–90.
10. Haile RW, Witte JS, Gold M, et al. The health effects of swimming in ocean water contaminated by storm drain runoff. Epidemiology. 1999;10:355–363.[Web of Science][Medline]
11. Arnold C, Gibbons J. Impervious surface coverage: the emergence of a key environmental indicator. J Am Plann Assoc. 1996;62:243–258.[Web of Science]
12. California’s Ocean Resources: An Agenda for the Future. Sacramento, Calif: California Resources Agency; 1997.
13. Young KD, Thackston EL. Housing density and bacterial loading in urban streams. J Environ Eng. 1999;125:1177–1180.
14. Mallin MA, Williams KE, Esham EC, Lowe RP. Effect of human development on bacteriological water quality in coastal watersheds. Ecological Applications. 2000;10:1047–1056.
15. Schueler TR. The importance of imperviousness. Watershed Protection Techniques. 1994;1:100–111.
16. Cabelli VJ, Dufour AP, McCabe LJ, Levin MA. Swimming-associated gastroenteritis and water quality. Am J Epidemiol. 1982;115:606–616.
17. Kay D, Fleisher JM, Salmon RL, et al. Predicting likelihood of gastroenteritis from sea bathing: results from randomized exposure. Lancet. 1994;344:905–909.[Web of Science][Medline]
18. Fleisher JM, Jones F, Kay D, et al. Water and non-water related risk factors for gastroenteritis among bathers exposed to sewage-contaminated marine waters. Int J Epidemiol. 1993;22:698–708.
19. Seyfried PL, Tobin RS, Brown NE, Ness PF. A prospective study of swimming-related illness: I. Swimming-associated health risk. Am J Public Health. 1985;75:1068–1070.
20. Corbett SJ, Rubin GL, Curry GK, Kleinbaum DG. The health effects of swimming at Sydney beaches. Am J Public Health. 1993;83:1701–1706.
21. Fleisher JM, Kay D, Salmon RL, Jones F, Wyer MD, Godfree AF. Marine water contaminated with domestic sewage: non-enteric illnesses associated with bather exposure in the United Kingdom. Am J Public Health. 1996;86:1228–1234.
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