Recreational exposure to low concentrations of microcystins during an algal bloom in a small lake.

We measured microcystins in blood from people at risk for swallowing water or inhaling spray while swimming, water skiing, jet skiing, or boating during an algal bloom. We monitored water samples from a small lake as a Microcystis aeruginosa bloom developed. We recruited 97 people planning recreational activities in that lake and seven others who volunteered to recreate in a nearby bloom-free lake. We conducted our field study within a week of finding a 10-microg/L microcystin concentration. We analyzed water, air, and human blood samples for water quality, potential human pathogens, algal taxonomy, and microcystin concentrations. We interviewed study participants for demographic and current health symptom information. Water samples were assayed for potential respiratory viruses (adenoviruses and enteroviruses), but none were detected. We did find low concentrations of Escherichia coli, indicating fecal contamination. We found low levels of microcystins (2 microg/L to 5 microg/L) in the water and (<0.1 ng/m(3)) in the aerosol samples. Blood levels of microcystins for all participants were below the limit of detection (0.147 microg/L). Given this low exposure level, study participants reported no symptom increases following recreational exposure to microcystins. This is the first study to report that water-based recreational activities can expose people to very low concentrations of aerosol-borne microcystins; we recently conducted another field study to assess exposures to higher concentrations of these algal toxins.

Evaluation of an Ultrafiltration-Based Procedure for Simultaneous Recovery of Diverse Microbes in Source Waters.

In this study, hollow-fiber ultrafiltration (UF) was assessed for recovery of Escherichia coli, Clostridium perfringens spores, Cryptosporidium parvum oocysts, echovirus 1, and bacteriophages MS2 and ΦX174 from ground and surface waters. Microbes were seeded into twenty-two 50-L water samples that were collected from the Southeastern United States and concentrated to ∼500 mL by UF. Secondary concentration was performed for C. parvum by centrifugation followed by immunomagnetic separation. Secondary concentration for viruses was performed using centrifugal ultrafilters or polyethylene glycol precipitation. Nine water quality parameters were measured in each water sample to determine whether water quality data correlated with UF and secondary concentration recovery efficiencies. Average UF recovery efficiencies were 66%-95% for the six enteric microbes. Average recovery efficiencies for the secondary concentration methods were 35%-95% for C. parvum and the viruses. Overall, measured water quality parameters were not significantly associated with UF recovery efficiencies. However, recovery of ΦX174 was negatively correlated with turbidity. The recovery data demonstrate that UF can be an effective method for concentrating diverse microbes from ground and surface waters. This study highlights the utility of tangential-flow hollow fiber ultrafiltration for recovery of bacteria, viruses, and parasites from large volume environmental water samples.

Hollow-fiber ultrafiltration for simultaneous recovery of viruses, bacteria and parasites from reclaimed water.

Hollow-fiber ultrafiltration (UF) is a technique that has been reported to be effective for recovering a diverse array of microbes from water, and may also be potentially useful for microbial monitoring of effluent from water reclamation facilities. However, few data are available to indicate the potential limitations and efficacy of the UF technique for treated wastewater. In this study, recovery efficiencies were determined for various options available for performing the tangential-flow UF technique, including hollow-fiber ultrafilter (i.e., dialyzer) type, ultrafilter pre-treatment (i.e., blocking), and elution. MS2 and ΦX174 bacteriophages, Clostridium perfringens spores, Escherichia coli, and Cryptosporidium parvum oocysts were seeded into 10-L reclaimed water samples to evaluate UF options. Then a single UF protocol was established and studied using seeded and non-seeded 100-L samples from two water reclamation facilities in Georgia, USA. Baxter Exeltra Plus 210 and Fresenius F200NR dialyzers were found to provide significantly higher microbial recovery than Minntech HPH 1400 hemoconcentrators. The selected final UF method incorporated use of a non-blocked ultrafilter for UF followed by elution using a surfactant-based solution. For 10-L samples, this method achieved recovery efficiencies of greater than 50% recovery of seeded viruses, bacteria, and parasites. There was no significant difference in overall microbial recovery efficiency when the method was applied to 10- and 100-L samples. In addition, detection levels for pathogens in seeded 100-L reclaimed water samples were 1000 PFU HAV, 10,000 GI norovirus particles, <500 Salmonella and <200 Cryptosporidium oocysts. These data demonstrate that UF can be an effective technique for recovering diverse microbes in reclaimed water to monitor and improve effluent water quality in wastewater treatment plants.

Viruses and bacteria in karst and fractured rock aquifers in East Tennessee, USA.

A survey of enteric viruses and indicator bacteria was carried out in eight community water supply sources (four wells and four springs) in East Tennessee. Seven sites derived their water from carbonate aquifers and one from fractured sandstone. Four of the sites were deemed "low-risk" based on prior monitoring of fecal indicators and factors such as presence of thick layers of overlying sediments. The remaining sites were deemed "high-risk." Enteric viruses (enterovirus and reovirus) were detected by cell culture at least once in seven of the eight wells or springs including all but one of the four low-risk sites. Viral RNA, however, was not detected in any of the samples by reverse transcription-polymerase chain reaction. Conventional indicators of microbial contamination (Escherichia coli and total coliform bacteria) were detected together with culturable viruses in seven of nine virus positive samples. Bacteroides, an alternative fecal indicator which has not previously been used in groundwater investigations, was also detected in all but one of the samples containing E. coli or total coliform bacteria, as well as in one sample where viruses were present in the absence of other bacterial indicators. The study highlights some of the challenges involved in surveys of virus occurrence and indicates that culturable enteric viruses in East Tennessee karst aquifers may be more widespread than previously observed in studies of karst aquifers in Pennsylvania (8%), the Ozark region of Missouri (< 1%), or several other states covered in a national microbial water quality survey conducted by the U.S. Environmental Protection Agency (43%).

Recreational exposure to microcystins during algal blooms in two California lakes.

We conducted a study of recreational exposure to microcystins among 81 children and adults planning recreational activities on either of three California reservoirs, two with significant, ongoing blooms of toxin-producing cyanobacteria, including Microcystis aeruginosa (Bloom Lakes), and one without a toxin-producing algal bloom (Control Lake). We analyzed water samples for algal taxonomy, microcystin concentrations, and potential respiratory viruses (adenoviruses and enteroviruses). We measured microcystins in personal air samples, nasal swabs, and blood samples. We interviewed study participants for demographic and health symptoms information. We found highly variable microcystin concentrations in Bloom Lakes (<10 microg/L to >500 microg/L); microcystin was not detected in the Control Lake. We did not detect adenoviruses or enteroviruses in any of the lakes. Low microcystin concentrations were found in personal air samples (<0.1 ng/m(3) [limit of detection]-2.89 ng/m(3)) and nasal swabs (<0.1 ng [limit of detection]-5 ng). Microcystin concentrations in the water-soluble fraction of all plasma samples were below the limit of detection (1.0 microg/L). Our findings indicate that recreational activities in water bodies that experience toxin-producing cyanobacterial blooms can generate aerosolized cyanotoxins, making inhalation a potential route of exposure. Future studies should include collecting nasal swabs to assess upper respiratory tract deposition of toxin-containing aerosols droplets.

Multistate evaluation of an ultrafiltration-based procedure for simultaneous recovery of enteric microbes in 100-liter tap water samples.

Ultrafiltration (UF) is increasingly being recognized as a potentially effective procedure for concentrating and recovering microbes from large volumes of water and treated wastewater. Because of their very small pore sizes, UF membranes are capable of simultaneously concentrating viruses, bacteria, and parasites based on size exclusion. In this study, a UF-based water sampling procedure was used to simultaneously recover representatives of these three microbial classes seeded into 100-liter samples of tap water collected from eight cities covering six hydrologic areas of the United States. The UF-based procedure included hollow-fiber UF as the primary step for concentrating microbes and then used membrane filtration for bacterial culture assays, immunomagnetic separation for parasite recovery and quantification, and centrifugal UF for secondary concentration of viruses. Water samples were tested for nine water quality parameters to investigate whether water quality data correlated with measured recovery efficiencies and molecular detection levels. Average total method recovery efficiencies were 71, 97, 120, 110, and 91% for phiX174 bacteriophage, MS2 bacteriophage, Enterococcus faecalis, Clostridium perfringens spores, and Cryptosporidium parvum oocysts, respectively. Real-time PCR and reverse transcription-PCR (RT-PCR) for seeded microbes and controls indicated that tap water quality could affect the analytical performance of molecular amplification assays, although no specific water quality parameter was found to correlate with reduced PCR or RT-PCR performance.