RESUMEN
For many coastal regions around the world, recreational beach water quality is assessed using fecal indicator bacteria (FIB). However, the utility of FIB as indicators of recreational water illness (RWI) risk has been questioned, particularly in coastal settings with no obvious sources of human sewage. In this study we employed a source-apportionment quantitative microbial risk assessment (SA-QMRA) to assess RWI risk at a popular semi-enclosed recreational beach in Southern California (Baby Beach, City of Dana Point) with no obvious point sources of human sewage. Our SA-QMRA results suggest that, during dry weather, the median RWI risk at this beach is below the U.S. EPA recreational water quality criteria (RWQC) of 36 illness cases per 1000 bathers. During wet weather, the median RWI risk predicted by SA-QMRA depends on the assumed level of human waste associated with stormwater; the RWI risk is below the EPA RWQC illness risk benchmark 100% of the time provided that <2% of the FIB in stormwater are of human origin. However, these QMRA outcomes contrast strongly with the EPA RWQC for 30-day geometric mean of enterococci bacteria. Our results suggest that SA-QMRA is a useful framework for estimating robust RWI risk that takes into account local information about possible human and non-human sources of FIB.
Asunto(s)
Playas , Microbiología del Agua , California , Monitoreo del Ambiente , Heces/microbiología , Humanos , Tiempo (Meteorología)RESUMEN
Marine beaches are important recreational and economic resources in Brazil, but the beaches' water quality is negatively impacted by the discharge of domestic sewage effluent. The occurrence of diarrheagenic Escherichiacoli among the E. coli isolated from three Brazilian marine beaches was investigated. Multiplex and single step PCR were used to screen 99 E. coli isolates for ten target toxin genes. Six toxin genes, stx1, eae, estp, esth, astA, and bfpA, were identified in 1% to 35% of the isolates. A quantitative microbial risk assessment (QMRA) of human exposure to diarrheagenic E. coli during marine recreation was carried out. The results indicated that the diarrheagenic E. coli risk is well below the U.S. EPA's recommended daily recreational risk benchmark. However, the overall recreational health risk due to all pathogens in the water could be much higher and exceeded the U.S. EPA's benchmark.
Asunto(s)
Playas , Escherichia coli/aislamiento & purificación , Escherichia coli/patogenicidad , Calidad del Agua , Brasil , Exposición a Riesgos Ambientales/análisis , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Proteínas Fimbrias/genética , Humanos , Reacción en Cadena de la Polimerasa Multiplex , Recreación , Medición de Riesgo/métodos , Aguas del Alcantarillado , Toxina Shiga I/genética , Estados Unidos , Eliminación de Residuos Líquidos , Microbiología del AguaRESUMEN
Capturing stormwater is becoming a new standard for sustainable urban stormwater management, which can be used to supplement water supply portfolios in water-stressed cities. The key advantage of harvesting stormwater is to use low impact development (LID) systems for treatment to meet water quality requirement for non-potable uses. However, the lack of scientific studies to validate the safety of such practice has limited its adoption. Microbial hazards in stormwater, especially human viruses, represent the primary public health threat. Using adenovirus and norovirus as target pathogens, we investigated the viral health risk associated with a generic scenario of urban stormwater harvesting practice and its application for three non-potable uses: 1) toilet flushing, 2) showering, and 3) food-crop irrigation. The Quantitative Microbial Risk Assessment (QMRA) results showed that food-crop irrigation has the highest annual viral infection risk (median range: 6.8×10(-4)-9.7×10(-1) per-person-per-year or pppy), followed by showering (3.6×10(-7)-4.3×10(-2)pppy), and toilet flushing (1.1×10(-7)-1.3×10(-4)pppy). Disease burden of each stormwater use was ranked in the same order as its viral infection risk: food-crop irrigation>showering>toilet flushing. The median and 95th percentile risk values of toilet-flushing using treated stormwater are below U.S. EPA annual risk benchmark of ≤10(-4)pppy, whereas the disease burdens of both toilet-flushing and showering are within the WHO recommended disease burdens of ≤10(-6)DALYspppy. However, the acceptability of showering risk interpreted based on the U.S. EPA and WHO benchmarks is in disagreement. These results confirm the safety of stormwater application in toilet flushing, but call for further research to fill the data gaps in risk modeling as well as risk benchmarks.
Asunto(s)
Monitoreo del Ambiente , Aguas Residuales/virología , Microbiología del Agua , Ciudades , Humanos , Salud Pública , Riesgo , Medición de RiesgoRESUMEN
Health risk concerns associated with household use of rooftop-harvested rainwater (HRW) constitute one of the main impediments to exploit the benefits of rainwater harvesting in the United States. However, the benchmark based on the U.S. EPA acceptable annual infection risk level of ≤1 case per 10,000 persons per year (≤10(-4) pppy) developed to aid drinking water regulations may be unnecessarily stringent for sustainable water practice. In this study, we challenge the current risk benchmark by quantifying the potential microbial risk associated with consumption of HRW-irrigated home produce and comparing it against the current risk benchmark. Microbial pathogen data for HRW and exposure rates reported in literature are applied to assess the potential microbial risk posed to household consumers of their homegrown produce. A Quantitative Microbial Risk Assessment (QMRA) model based on worst-case scenario (e.g. overhead irrigation, no pathogen inactivation) is applied to three crops that are most popular among home gardeners (lettuce, cucumbers, and tomatoes) and commonly consumed raw. The infection risks of household consumers attributed to consumption of these home produce vary with the type of produce. The lettuce presents the highest risk, which is followed by tomato and cucumber, respectively. Results show that the 95th percentile values of infection risk per intake event of home produce are one to three orders of magnitude (10(-7) to 10(-5)) lower than U.S. EPA risk benchmark (≤10(-4) pppy). However, annual infection risks under the same scenario (multiple intake events in a year) are very likely to exceed the risk benchmark by one order of magnitude in some cases. Estimated 95th percentile values of the annual risk are in the 10(-4) to 10(-3) pppy range, which are still lower than the 10(-3) to 10(-1) pppy risk range of reclaimed water irrigated produce estimated in comparable studies. We further discuss the desirability of HRW for irrigating home produce based on the relative risk of HRW to reclaimed wastewater for irrigation of food crops. The appropriateness of the ≤10(-4) pppy risk benchmark for assessing safety level of HRW-irrigated fresh produce is questioned by considering the assumptions made for the QMRA model. Consequently, the need of an updated approach to assess appropriateness of sustainable water practice for making guidelines and policies is proposed.
Asunto(s)
Riego Agrícola , Medición de Riesgo/métodos , Microbiología del Agua , Cucumis sativus/crecimiento & desarrollo , Cucumis sativus/microbiología , Agua Potable/microbiología , Agua Potable/normas , Contaminación de Alimentos/análisis , Humanos , Infecciones/microbiología , Lactuca/crecimiento & desarrollo , Lactuca/microbiología , Solanum lycopersicum/crecimiento & desarrollo , Solanum lycopersicum/microbiología , Modelos Teóricos , Lluvia , Estados Unidos , AguaRESUMEN
This study investigated the occurrence of three types of vibrios in Southern California recreational beach waters during the peak marine bathing season in 2007. Over 160 water samples were concentrated and enriched for the detection of vibrios. Four sets of PCR primers, specific for Vibrio cholerae, V. parahaemolyticus, and V. vulnificus species and the V. parahaemolyticus toxin gene, respectively, were used for the amplification of bacterial genomic DNA. Of 66 samples from Doheny State Beach, CA, 40.1% were positive for V. cholerae and 27.3% were positive for V. parahaemolyticus, and 1 sample (1.5%) was positive for the V. parahaemolyticus toxin gene. Of the 96 samples from Avalon Harbor, CA, 18.7% were positive for V. cholerae, 69.8% were positive for V. parahaemolyticus, and 5.2% were positive for the V. parahaemolyticus toxin gene. The detection of the V. cholerae genetic marker was significantly more frequent at Doheny State Beach, while the detection of the V. parahaemolyticus genetic marker was significantly more frequent at Avalon Harbor. A probability-of-illness model for V. parahaemolyticus was applied to the data. The risk for bathers exposed to recreational waters at two beaches was evaluated through Monte Carlo simulation techniques. The results suggest that the microbial risk from vibrios during beach recreation was below the illness benchmark set by the U.S. EPA. However, the risk varied with location and the type of water recreation activities. Surfers and children were exposed to a higher risk of vibrio diseases. Microbial risk assessment can serve as a useful tool for the management of risk related to opportunistic marine pathogens.
Asunto(s)
Toxinas Bacterianas/genética , Playas , Agua de Mar/microbiología , Vibriosis/epidemiología , Vibrio cholerae/aislamiento & purificación , Vibrio parahaemolyticus/aislamiento & purificación , Vibrio vulnificus/aislamiento & purificación , California , Cartilla de ADN/genética , Humanos , Reacción en Cadena de la Polimerasa , Medición de Riesgo , Vibrio cholerae/genética , Vibrio parahaemolyticus/genética , Vibrio vulnificus/genéticaRESUMEN
Environmental agencies are given the task of monitoring water quality in rivers, lakes, and other bodies of water, for the purpose of comparing the results with regulatory standards. Monitoring follows requirements set by regulations, and data are collected in a systematic way for the intended purpose. Monitoring enables agencies to determine whether water bodies are polluted. Much effort is spent per monitoring event, resulting in hundreds of data points typically used solely for comparison with regulatory standards and then stored for little further use. This paper devises a data analysis methodology that can make use of the pre-existing datasets to extract more useful information on water quality trends, without new sample collection and analysis. In this paper, measured lake water quality data are subjected to statistical analyses including Principal Component Analysis (PCA) to deduce changes in water quality spatially and temporally over several years. It was found that the lake as a whole changed temporally by season, rather than spatially. Storm events caused the greatest shifts in water quality, though the shifts were fairly consistent across sampling stations. This methodology can be applied to similar datasets, especially with the recent emphasis by the U.S. EPA on protection of lakes as water sources. Water quality managers using these techniques may be able to lower their monitoring costs by eliminating redundant water quality parameters found in this analysis.