Guoqing He

The BEACHES Study: health effects and exposures from non-point source microbial contaminants in subtropical recreational marine waters

BACKGROUND Microbial water-quality indicators, in high concentrations in sewage, are used to determine whether water is safe for recreational purposes. Recently, the use of these indicators to regulate recreational water bodies, particularly in sub/tropical recreational marine waters without known sources of sewage, has been questioned. The objectives of this study were to evaluate the risk to humans from exposure to subtropical recreational marine waters with no known point source, and the possible relationship between microbe densities and reported symptoms in human subjects with random-exposure assignment and intensive individual microbial monitoring in this environment. METHODS A total of 1303 adult regular bathers were randomly assigned to bather and non-bather groups, with subsequent follow-up for reported illness, in conjunction with extensive environmental sampling of indicator organisms (enterococci). RESULTS Bathers were 1.76 times more likely to report gastrointestinal illness [95% confidence interval (CI) 0.94-3.30; P = 0.07]; 4.46 times more likely to report acute febrile respiratory illness (95% CI 0.99-20.90; P = 0.051) and 5.91 times more likely to report a skin illness (95% CI 2.76-12.63; P < 0.0001) relative to non-bathers. Evidence of a dose-response relationship was found between skin illnesses and increasing enterococci exposure among bathers [1.46 times (95% CI 0.97-2.21; P = 0.07) per increasing log(10) unit of enterococci exposure], but not for gastrointestinal or respiratory illnesses. CONCLUSIONS This study indicated that bathers may be at increased risk of several illnesses relative to non-bathers, even in the absence of any known source of domestic sewage impacting the recreational marine waters. There was no dose-response relationship between gastroenteritis and increasing exposure to enterococci, even though many current water-monitoring standards use gastroenteritis as the major outcome illness.

Traditional and molecular analyses for fecal indicator bacteria in non-point source subtropical recreational marine waters.

The use of enterococci as the primary fecal indicator bacteria (FIB) for the determination of recreational water safety has been questioned, particularly in sub/tropical marine waters without known point sources of sewage. Alternative FIB (such as the Bacteroidales group) and alternative measurement methods (such as rapid molecular testing) have been proposed to supplement or replace current marine water quality testing methods which require culturing enterococci. Moreover, environmental parameters have also been proposed to supplement current monitoring programs. The objective of this study was to evaluate the health risks to humans from exposure to subtropical recreational marine waters with no known point source. The study reported symptoms between one set of human subjects randomly assigned to marine water exposure with intensive environmental monitoring compared with other subjects who did not have exposure. In addition, illness outcomes among the exposed bathers were compared to levels of traditional and alternative FIB (as measured by culture-based and molecular-based methods), and compared to easily measured environmental parameters. Results demonstrated an increase in self-reported gastrointestinal, respiratory and skin illnesses among bathers vs. non-bathers. Among the bathers, a dose-response relationship by logistic regression modeling was observed for skin illness, where illness was positively related to enterococci enumeration by membrane filtration (odds ratio = 1.46 [95% confidence interval = 0.97-2.21] per increasing log10 unit of enterococci exposure) and positively related to 24 h antecedent rain fall (1.04 [1.01-1.07] per increasing millimeters of rain). Acute febrile respiratory illness was inversely related to water temperature (0.74 [0.56-0.98] per increasing degree of water temperature). There were no significant dose-response relationships between report of human illness and any of the other FIB or environmental measures. Therefore, for non-point source subtropical recreational marine waters, this study suggests that humans may be at increased risk of reported illness, and that the currently recommended and investigational FIB may not track gastrointestinal illness under these conditions; the relationship between other human illness and environmental measures is less clear.

Evaluation of conventional and alternative monitoring methods for a recreational marine beach with nonpoint source of fecal contamination.

The objectives of this work were to compare enterococci (ENT) measurements based on the membrane filter, ENT(MF) with alternatives that can provide faster results including alternative enterococci methods (e.g., chromogenic substrate (CS), and quantitative polymerase chain reaction (qPCR)), and results from regression models based upon environmental parameters that can be measured in real-time. ENT(MF) were also compared to source tracking markers (Staphylococcus aureus, Bacteroidales human and dog markers, and Catellicoccus gull marker) in an effort to interpret the variability of the signal. Results showed that concentrations of enterococci based upon MF (<2 to 3320 CFU/100 mL) were significantly different from the CS and qPCR methods (p < 0.01). The correlations between MF and CS (r = 0.58, p < 0.01) were stronger than between MF and qPCR (r ≤ 0.36, p < 0.01). Enterococci levels by MF, CS, and qPCR methods were positively correlated with turbidity and tidal height. Enterococci by MF and CS were also inversely correlated with solar radiation but enterococci by qPCR was not. The regression model based on environmental variables provided fair qualitative predictions of enterococci by MF in real-time, for daily geometric mean levels, but not for individual samples. Overall, ENT(MF) was not significantly correlated with source tracking markers with the exception of samples collected during one storm event. The inability of the regression model to predict ENT(MF) levels for individual samples is likely due to the different sources of ENT impacting the beach at any given time, making it particularly difficult to to predict short-term variability of ENT(MF) for environmental parameters.

Daily measures of microbes and human health at a non-point source marine beach

Studies evaluating the relationship between microbes and human health at non-point source beaches are necessary for establishing criteria which would protect public health while minimizing economic burdens. The objective of this study was to evaluate water quality and daily cumulative health effects (gastrointestinal, skin, and respiratory illnesses) for bathers at a non-point source subtropical marine recreational beach in order to better understand the inter-relationships between these factors and hence improve monitoring and pollution prevention techniques. Daily composite samples were collected, during the Oceans and Human Health Beach Exposure Assessment and Characterization Health Epidemiologic Study conducted in Miami (Florida, USA) at a non-point source beach, and analyzed for several pathogens, microbial source tracking markers, indicator microbes, and environmental parameters. Analysis demonstrated that rainfall and tide were more influential, when compared to other environmental factors and source tracking markers, in determining the presence of both indicator microbes and pathogens. Antecedent rainfall and F+ coliphage detection in water should be further assessed to confirm their possible association with skin and gastrointestinal (GI) illness outcomes, respectively. The results of this research illustrate the potential complexity of beach systems characterized by non-point sources, and how more novel and comprehensive approaches are needed to assess beach water quality for the purpose of protecting bather health.

Material Emission Parameters Obtained Through Regression

Diffusion coefficients (D) and partition coefficients (K) of volatile organic compounds (VOCs) from 20 dry building materials were obtained by fitting the predictions using a simplified diffusion model with small-scale chamber data. The materials analysed included 6 carpets, 3 particle boards, 3 plywood boards, 3 gypsum boards, 2 orient stranded boards, 2 acoustic ceiling tiles and 1 under pad. The types of VOCs studied included alkanes, alkenes, alkynes and benzene group compounds, with carbon number ranging from 1 to 15. The regression results include the optimal values and a sensitivity range of D and K. For the 4 alkanes emitted from 6 different carpets, a correlation trend was observed between the D, K and VOC properties (molecular weight and vapour pressure). However, the emission parameters in general are suggested to be related to both the molecular structure of compounds and material properties.

Experimental measurements of the flow resistance and inductance of inertance tubes at high acoustic amplitudes

We measured the flow resistance and flow inductance of inertance tubes at high acoustic amplitudes for four different inner diameters of 0.6, 1.0, 1.5 and 2.0 mm at various tube length ranging from 100 to 1500 mm, at frequencies of 30, 40, 50, 60 and 70 Hz. The experiments were carried out under system mean pressure of 20 bar at room temperature. The experimental data were compared with the explicit solution to the linear momentum equation for small acoustic amplitudes and were fitted with the modification coefficients in terms of the operating frequency and Reynolds numbers characterized by the amplitude of gas velocities.