Emission and dispersal of antibiotic resistance genes through bioaerosols generated during the treatment of municipal sewage.

Wastewater treatment plants act as socio-ecological couplers through the concentration, treatment, and subsequent environmental release of sewage collected from surrounding communities and are often considered hotspots for antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). While studies have identified the release of ARB/ARGs in treated liquid sewage, little is known about potential dispersal through wastewater bioaerosol emissions. The aim of this study was to better define the contribution of WWTP bioaerosols to potential environmental distribution of ARB/ARGs.

Modeling an irritant gas plume for epidemiologic study.

Plume dispersion modeling systems are often used in assessing human exposures to chemical hazards for epidemiologic study. We modeled the 2005 Graniteville, South Carolina, 54,915 kg railcar chlorine release using both the Areal Locations of Hazardous Atmospheres and Hazard Prediction and Assessment Capability (HPAC) plume modeling systems. We estimated the release rate by an engineering analysis combining semi-quantitative observations and fundamental physical principles.

Exposure models for the prior distribution in bayesian decision analysis for occupational hygiene decision making.

This study introduces two semi-quantitative methods, Structured Subjective Assessment (SSA) and Control of Substances Hazardous to Health (COSHH) Essentials, in conjunction with two-dimensional Monte Carlo simulations for determining prior probabilities. Prior distribution using expert judgment was included for comparison. Practical applications of the proposed methods were demonstrated using personal exposure measurements of isoamyl acetate in an electronics manufacturing facility and of isopropanol in a printing shop.

Characterization and control of the microbial community affiliated with copper or aluminum heat exchangers of HVAC systems.

Microbial growth in heating ventilation and air-conditioning (HVAC) systems with the subsequent contamination of indoor air is of increasing concern. Microbes and the subsequent biofilms grow easily within heat exchangers. A comparative study where heat exchangers fabricated from antimicrobial copper were evaluated for their ability to limit microbial growth was conducted using a full-scale HVAC system under conditions of normal flow rates using single-pass outside air.

Association between barracks type and acute respiratory infection in a gender integrated Army basic combat training population.

Background: Acute respiratory infections (ARIs) are the leading cause of acute morbidity and lost work time in the United States. Few studies have looked at building design and transmission of ARIs.

Objectives: This study explores the association of ventilation design, room occupancy numbers, and training week with ARI rates in Army Basic Combat Training barracks.

Deriving realistic source boundary conditions for a CFD simulation of concentrations in workroom air.

Computational fluid dynamics (CFD) is used increasingly to simulate the distribution of airborne contaminants in enclosed spaces for exposure assessment and control, but the importance of realistic boundary conditions is often not fully appreciated. In a workroom for manufacturing capacitors, full-shift samples for isoamyl acetate (IAA) were collected for 3 days at 16 locations, and velocities were measured at supply grills and at various points near the source. Then, velocity and concentration fields were simulated by 3-dimensional steady-state CFD using 295K tetrahedral cells, the k-ε turbulence model, standard wall function, and convergence criteria of 10(-6) for all scalars.

MALDI-TOF mass spectrometry speciation of staphylococci and their discrimination from micrococci isolated from indoor air of schoolrooms.

The focus of our work is the identification of medically relevant staphylococci from the environment; these organisms are among the major opportunistic pathogens associated with human disease. Andersen sampling was performed in schoolrooms during the school year. Eleven of thirty six isolates (all Gram-positive tetrads) were identified as staphylococci and 23 were characterized as micrococci.

Estimation of required monitoring time for obtaining validation data in enclosed spaces.

Methods for estimating airborne contaminant concentrations at specific locations within enclosed spaces, such as mathematical models and computational fluid dynamics (CFD), often are validated against directly measured concentrations. However, concentration variation with time introduces uncertainty into the measured concentration. Failure to determine monitoring time requirements can lead to errors in quantifying representative concentrations, which are likely to be attributed to errors in the method being validated.

Human K10 epithelial keratin is the most abundant protein in airborne dust of both occupied and unoccupied school rooms.

Previously it was demonstrated that the levels of large particles (>2 micron) and associated bacterial cell envelope markers increase greatly on occupation in schools; it was hypothesized that the source of both was shed human skin. In the current work to test this hypothesis, room air cleaners were used to collect airborne dust (>50-100 mg) from occupied and unoccupied school rooms which was then subjected to proteomic analysis. Proteins were extracted from the dust and separated using two dimensional gel electrophoresis (2D GE).

The effect of worker's location, orientation, and activity on exposure.

The impact of a worker's location, orientation, and activity was studied in an experimental room (2.86 m x 2.35 m x 2.

A second look at the Palmes' diffusive sampler.

The Palmes' tube, the first diffusive sampler incorporating a fixed path length, has received wide usage for the sampling of a large number of gaseous pollutants. But despite numerous previous studies, questions remain regarding the accuracy of these inexpensive, simple-to-construct, open-ended samplers. Here the mass transfer resistance in a Palmes' diffusive sampler was measured using the loss of cyclohexane from a Palmes' tube containing liquid cyclohexane at its base.

The effect of temperature differences on the distribution of an airborne contaminant in an experimental room.

Estimating exposure to contaminants emitted into workroom air is essential for worker protection. Although contaminant concentrations are often not spatially uniform within workrooms, many methods for estimating exposure do not adequately account for this variability. Here the impact of temperature differences within a room on spatial contaminant distribution was studied.

Coastal terrorism: using tabletop discussions to enhance coastal community infrastructure through relationship building.

The unique vulnerability of the nation's ports to terrorist attacks and other major disasters requires development of specialized training approaches that integrate and connect critical stakeholders. In 2003, the University of South Carolina Center for Public Health Preparedness developed and held its first Coastal Terrorism workshop in conjunction with the National Oceanic and Atmospheric Administration. Key federal, regional, state, and coastal agency leaders were invited to the 2-day event to explore, in a no-risk environment, the crucial role that public health agencies would play in a covert biological agent incident aboard a cruise ship.

Emergency preparedness academy adds public health to readiness equation.

From November 2003 to May 2004, the University of South Carolina Center for Public Health Preparedness and the South Carolina Department of Health and Environmental Control co-sponsored a 6-month-long Academy for Public Health Emergency Preparedness. Six-member teams made up of public health staff and community partner representatives (N = 78) attended from their respective health districts. The Academy consisted of three 6-day training sessions designed to prepare the teams to complete a team-based covert biological bioterrorism tabletop exercise.

Large particles are responsible for elevated bacterial marker levels in school air upon occupation.

Muramic acid (Mur) is found in bacterial peptidoglycan (PG) whereas 3-hydroxy fatty acids (3-OH FAs) are found in Gram-negative bacterial lipopolysaccharide (LPS). Thus Mur and 3-OH FAs serve as markers to assess bacterial levels in indoor air. An initial survey, in a school, demonstrated that the levels of dust, PG and LPS (pmol m(-3)) were each much higher in occupied rooms than in the same rooms when unoccupied.

Scale and shape issues in focused cluster power for count data.

BACKGROUND: Interest in the development of statistical methods for disease cluster detection has experienced rapid growth in recent years. Evaluations of statistical power provide important information for the selection of an appropriate statistical method in environmentally-related disease cluster investigations. Published power evaluations have not yet addressed the use of models for focused cluster detection and have not fully investigated the issues of disease cluster scale and shape.

Comparison of emission models with computational fluid dynamic simulation and a proposed improved model.

Understanding source behavior is important in controlling exposure to airborne contaminants. Industrial hygienists are often asked to infer emission information from room concentration data. This is not easily done, but models that make simplifying assumptions regarding contaminant transport are frequently used.

Increased levels of bacterial markers and CO2 in occupied school rooms.

Our group previously demonstrated that carbon dioxide (CO2) levels in heavily occupied schools correlate with the levels of airborne bacterial markers. Since CO2 is derived from the room occupants, it was hypothesized that in schools, bacterial markers may be primarily increased in indoor air because of the presence of children; directly from skin microflora or indirectly, by stirring up dust from carpets and other sources. The purpose of this project was to test the hypothesis.

Performance of deterministic workplace exposure assessment models for various contaminant source, air inlet, and exhaust locations.

Contaminant concentration estimates from simple models were compared with concentration fields obtained by computational fluid dynamic (CFD) simulations for various room and source configurations under steady-state conditions. Airflow and contaminant distributions in a 10 x 3 x 7-m room with a single contaminant source on a 1-m high table were simulated using CFD for steady, isothermal conditions. For a high wall jet inlet, simulations were performed for nine room air exhaust locations and eight source locations.

An investigation of air inlet velocity in simulating the dispersion of indoor contaminants via computational fluid dynamics.

Computational fluid dynamics (CFD) is potentially a valuable tool for simulating the dispersion of air contaminants in workrooms. However, CFD-estimated airflow and contaminant concentration patterns have not always shown good agreement with experimental results. Thus, understanding the factors affecting the accuracy of such simulations is critical for their successful application in occupational hygiene.

Improving the use of mixing factors for dilution ventilation design.

In specifying dilution ventilation flow rate, a safety factor, K, is often used to provide a margin of safety and to compensate for uncertainties and health impact severity. In current practice, the selection of K is very subjective. Here the component of K accounting for imperfect mixing, Km, was studied to develop more effective and efficient design procedures.