Bruce Lighthart's research while affiliated with United States Environmental Protection Agency and other places

Publications (60)

Article
The most prevalent microorganisms, viruses, bacteria, and fungi, are introduced into the atmosphere from many anthropogenic sources such as agricultural, industrial and urban activities, termed microbial air pollution (MAP), and natural sources. These include soil, vegetation, and ocean surfaces that have been disturbed by atmospheric turbulence. T...
Article
A set of simultaneously collected quantitative measurements of 12 meteorological and 6 culturable atmospheric bacterial (CAB) variables was made over a grass seed field during several early, mid, and late summer days. The observation site was located between the Cascade and Coastal Mountain Ranges near Corvallis in the Willamette Valley, Oregon. Pr...
Article
Abstract— The percentage of pigmented to total bacteria in the outdoor atmospheric population was studied in the field and in controlled laboratory experiments to evaluate the effects of solar radiation (SR) on bacterial survival. The field experiments showed that the percentage of pigmented bacteria positively correlated with SR activity during cl...
Article
This MiniReview is concerned with the sources, flux and the spacial and temporal distributions of culturable airborne bacteria; how meteorological conditions modulate these distributions; and how death, culture media, and experimental devices relate to measuring airborne bacteria. Solar radiation is thought to be the planetary driver of the annual...
Article
Slit and Andersen cascade impact samplers were used to collect ambient atmospheric bacteria under clear conditions at noon and night onto Luria-Bertani agar surfaces. The bacteria were then directly exposed to simulated solar radiation (SSR) for increasing periods to evaluate the lethal effect of SSR. The results showed that SSR had marked differen...
Article
Tethered honey bees (Apidea Apis melifera) coaxed to fly in a miniature wind tunnel for a specific time interval, adsorb a virus (i.e., bacteriophage MS2) aerosol at a linear rate of 1% of the aerosol concentration for every 6.73 pC of electrostatic charge on the bee.
Article
An aerosol cloud of Bacillus atrophaeus (previously B. subtilis variety niger) spores, an anthrax surrogate, was created in a large 0.4ha (1 ac), bee-containing, open-mesh tent. Bees from a B. atrophaeus uncontaminated hive flying through the cloud adsorbed the spores in statistically significant quantities. After removal of the B. atrophaeus conta...
Article
Full-text available
It has been shown that honey bees (Apis mellifera L.) adsorb bacterial spores as a function of the electrostatic charge on the bee and concentration of bacteria in the aerosol during tethered flight in wind tunnel experiments. This report presents a mathematical model for predicting the number of spores that could be adsorbed onto free-flying bees...
Article
Full-text available
An air conditioned wind tunnel system was designed, fabricated, and tested to determine whether tethered bees scavenge microbeads or Bacillus subtilis var. niger spores from aerosols. Tests showed that microbeads and spores were scavenged by bumblebees and honeybees, respectively. Five independent variables and their interactions were used in a ste...
Article
Airborne bacterial samples were collected using wet cyclone and cascade impact samplers 2 to 3 times a week at 2 agricultural sites in the mid-Willamette River valley, near Corvallis, OR during 1997. The concentrations of total (TB), culturable (CB), and particulate-associated culturable (PACB) bacteria in the ambient atmosphere were measured using...
Article
Variations in the atmospheric surface layer's culturable, and to a lesser extent, total bacteria-associated atmospheric particlecharacteristics will be discussed in terms of (a)their temporal variation from 2 min resolutionthrough diurnal to annual periods, (b) the effect ofmeteorological conditions on their abundance andsize, (c) total to culturab...
Article
An hypothesis is presented that describes, in general terms, the temporal and spatial airborne bacterial distribution patterns in the mixed layer of the planetary atmosphere. It is hypothesized that the near coincidence of the solar radiation cycle and temporal atmospheric bacterial distribution patterns indicate that the bacterial distribution in...
Article
Alfresco (def. clean, outdoor) airborne bacteria were collected with a commercially available wet-cyclone bioaerosol sampler to demonstrate its use, sample processing and resultant observations of total and culturable bacteria in mid-summer in the mid-Willamette River Valley, OR. Some critiques of the system are given. The maximum and minimum total...
Article
We tested the effect of 2 exposure methods and 2 environmental factors, temperature and humidity, on Beauveria bassiana (Deuteromycotina: Hyphomycetes) mycosis in Hippodamia convergens Guérin-Méneville (Coleoptera: Coccinellidae). We found that the standard EPA bioassay method of exposing nontarget insects by immersion resulted in a per-insect dose...
Article
A model was prepared to simulate the observed concentration dynamics of culturable bacteria in the diurnal summer atmosphere at a Willamette River Valley, Oregon location. The meteorological and bacterial mechanisms included in a dynamic null-dimensional model with one-second time step are solar radiation, convective mixed layer depth, bacterial co...
Article
Two test vegetative bacteria, Pseudomonas syringae and Erwinia herbicola, and a physical aerosol decay indicator, Bacillus subtilis var. niger spores, were sprayed into a particle size fractionating wind tunnel. Test bacterial survival significantly increased directly with droplet size for varying test cell to spore ratios and temperature. However,...
Article
Ambient heterogenic atmospheric bacteria were collected by impaction directly onto nutrient agar surfaces on clear sunny and cloudy days and at night. Samples were then exposed to summer noontime solar radiation (SR) for increasing periods of time. Bacterial survival was the least for the organisms collected at nighttime and the greatest for those...
Article
To determine the risks of microbial air pollution from microorganisms used for pesticides and bioremediation, or emanating from composting, fermentation tanks, or other agricultural and urban sources, airborne microbial levels must be evaluated. This study surveyed the atmospheric load of culturable bacteria at four locations in Oregon: a city stre...
Article
Several strains of the entomopathogenic fungus Beauveria bassiana have been considered for use as microbial insecticides. Experimental sprays were conducted in an alfalfa field with an aphid-derived strain of B. bassiana to determine its persistence and its effects on pea aphids, Acyrthosiphon pisum (Homoptera: Aphididae) and a non-target aphid pre...
Article
Full-text available
The microorganisms Escherichia coli DH5 alpha and Bacillus thuringiensis HD-1 show an increased tolerance to freeze-drying when dried in the presence of the disaccharides trehalose and sucrose. When the bacteria were dried with 100 mM trehalose, 70% of the E. coli and 57% of the B. thuringiensis organisms survived, compared with 56 and 44%, respect...
Article
The observed deposition pattern from a field spray ofBacillus subtilus var.niger spores is compared with that of a computer simulated bioaerosol particle dispersion model. Using the same meteorological conditions as the field spray, the model produced a bioaerosol deposition pattern estimated to be reasonably similar (R 2=0.66) to the observed fiel...
Article
Temporal airborne bacterial concentrations and meteorological conditions were measured above a grass seed field in the Willamette River Valley, near Corvallis, Oreg., in the summer of 1993. The concentration of airborne bacteria had a maximum of 1,368.5 CFU/m(sup3), with a coefficient of variation of 90.5% and a mean of 121.3 CFU/m(sup3). The lowes...
Article
The viable bacterial particle size distribution in the atmosphere at the Hanford Nuclear Reservation, Richland, WA during two, 1-week periods in June 1992, was observed at three intervals during the day (morning, midday and evening) and at three heights (2, 4, and 8 m) above ground level. The distributions were significantly different (P=0.01) betw...
Article
Summary Aerosol survival of a genetically engineered strain ofEscherichia coli demonstrated a more rapid die-off (i.e., death rate) compared to its parental wildtype. Up to 77% of a freeze dried and air-exposed genetically engineered microorganism (GEM) and wildtype bacteria could be resuscitated by the amendment of the dilution medium with catalas...
Article
Estimates of the bacterial flux for a daylight cycle were observed at the Hanford Nuclear Reservation, Richland, WA, during June 1992, using a modified Bowen ratio method. The upward daytime bacterial flux was coupled with the solar radiation/sensible heat cycle, but commenced 2 h later in the morning and ceased 3 h earlier in the afternoon. During...
Chapter
Bioaerosol droplets may be generated from a suspension of microorganisms sprayed into the atmosphere as a polydipersed aerosol, that is, a dispersion made up of many different sized droplets. There, each droplet follows its unique trajectory all the while evaporating to a packed residue of particles. The shape and size of the residue particle depen...
Chapter
Bioaerosols may be generated from a liquid suspension of microorganisms, or upon drying from a dust or powder. Man makes use of both suspensions and powders of microorganisms in his biotechnological applications in manufacturing, agriculture, and forestry. Although, airborne, the deleterious effects of the stressful atmospheric conditions may damag...
Chapter
Although the atmosphere forms a continuous bioaerosol transport medium between indoor and outdoor air, barriers occur that hinder airflow. Because of these hinderances, it has been assumed that it is adequate to study these two environments separately. As more is learned about both populations, this assumption may need to be changed.
Chapter
Many bioaerosol models have been prepared ranging from compartment models (Forrester, 1961; Atkins, 1969), describing the downwind concentrations and flux (i.e., D/P transfer rate where D/P is a droplet/particle; D/P/M−2 s−1) of bioaerosols from a source that contributes to the loading of the bulk atmosphere (Fig. 9.1) through comprehensive, theore...
Chapter
Bioaerosol monitoring is a rapidly emerging area of industrial hygiene that is finding increased use and overuse. It is often used in conjunction with indoor environment quality investigations, infectious disease outbreaks, and agricultural health investigations. Bioaerosol monitoring includes the measurement of viable (culturable and nonculturable...
Article
A bioaerosol research chamber was constructed and used to evaluate wind-gust release of previously depositedPseudomonas syringae, spores ofBacillus subtilis var.niger, and fluorescent microspheres (FM) on oat plants, and the airborne survival of the releasedP. syringae. Observations of wind gusts on the releasedBacillus spores and FM showed they ha...
Article
Freeze-dried cultures of wild-type and genetically engineered strains of Escherichia coli lost their colony-forming ability upon exposure to air, visible light, and certain relative humidity levels. Both strains could be maximally protected from these lethal effects with 100 mM trehalose, a concentration calculated to just saturate the interphospho...
Article
The microbial insecticide Bacillus thuringiensis Berliner var. kurstaki is used to control forest pests in regions where tansy ragwort, Senecio jacobaea L., occurs. Biological control of this noxious weed may be compromised if the cinnabar moth, Tyria jacobaeae (L.), is susceptible to B. thuringiensis. In laboratory feeding tests, we found that fol...
Article
Full-text available
Because the death mechanisms of freeze-dried and air-dried bacteria are thought to be similar, freeze-drying was used to investigate the survival differences between potentially airborne genetically engineered microorganisms and their wild types. To this end, engineered strains of Escherichia coli and Pseudomonas syringae were freeze-dried and expo...
Article
We tested the effects of larval age and stress on the susceptibility of the convergent lady beetle (Hippodamia convergens) to the weakly pathogenic bacterium Pseudomonas fluorescens. To test for the effects of larval age, the dose response to the bacterium was determined for each instar. The LC50s for first, second, and third instars (4.8 × 109, 2....
Article
Catalase incorporation into enumeration media caused a significant increase (greater than 63%) in the colony-forming abilities of airborne bacteria. Incubation for 30 to 60 min of airborne bacteria in collection fluid containing catalase caused a greater than 95% increase in colony-forming ability. However, catalase did not have any effects on enum...
Article
Simulated droplet trajectories of a polydispersed microbial aerosol in a laminar air flow regimen were compared with observed dispersal patterns of aerosolized Bacillus subtilis subsp. niger spores in quasilaminar airflow. Simulated dispersal patterns could be explained in terms of initial droplet sizes and whether the droplets evaporated to residu...
Article
The osmoprotectant betaine was incorporated into collection fluid and enumeration medium to determine its effects on the colony-forming abilities of airborne bacteria, which were collected from three separate locations: a wastewater treatment plant, the roof of a laboratory building, and an unobstructed farmland. At all locations, addition of 2 to...
Article
Infective stage juveniles of the entomogenous rhabditoid nematodes, Neoaplectana carpocapsae (Steinernematidae) and Heterorhabditis heliothidis (Heterorhabditidae) were not affected when placed in commercial preparations of Bacillus thuringiensis var. san diego, israelensis and kurstaki. However, nematode development in larvae of the elm-leaf beetl...
Article
From 270 published laboratory airborne death rate measurements, two regression models relating the death rate constant for 15 bacterial species to aerosol age in the dark, Gram reaction, temperature, and an evaporation factor which is a function of RH and temperature were obtained. The independent variables accounted for 94% of the variation in the...
Article
The framework for a simulation model which describes the dispersion of individual droplets of water containing viable microbes is presented. The model accounts for physical, chemical, biological, and measured meteorological parameters of each droplet at each of many short time steps. Repeating the modeling process for many droplets will simulate a...
Article
The framework for a simulation model which describes the dispersion of individual droplets of water containing viable microbes is presented. The model accounts for physical, chemical, biological, and measured meteorological parameters of each droplet at each of many short time steps. Repeating the modeling process for many droplets will simulate a...
Article
Temperature, starvation, and nutrition stresses, applied singly and in combination, significantly affected the susceptibility of Chrysoperla carnea to Beauveria bassiana and varied in effectiveness according to insect age and gender. The nutrition stress caused the most significant increase in adult and larval mortality and larval developmental fai...
Article
Removal of Peridroma saucia from the field to the laboratory caused little change in the quantity of facultative and aerobic bacteria in the gut but produced significant qualitative and quantitative changes in distinguishable groups of the family Enterobacteriaceae in the gut.
Article
A Metaseiulus occidentalis bioassay procedure that approaches incubation conditions for maximum host susceptibility to Serratia marcescens is presented. Preinoculation temperature and/or starvation pulses, chronic RH and crowding (or food search area) stressors, and an age (or instar) modulator were used singly and in combination to observe effects...
Article
A Gaussian plume model has been modified to include an airborne microbial survival term that is a best-fit function of laboratory experimental data of weather variables. The model has been included in an algorithm using microbial source strength and local hourly mean weather data to drive the model through a summer- and winter-day cycle. For illust...
Article
The formulation, testing protocol, lethal effects, sub-lethal effects, ecological relationships and selectivity of microbial pesticides on non-target, beneficial arthropod natural enemies of insect and mite pests are reviewed for viruses, bacteria, fungi and protozoa. In general, it was found that: (1) effects from indirect mortality of natural ene...
Article
An extensive series of laboratory experiments was conducted in soil microcosms to study the respiratory response of microorganisms to toxicant amendments within different types of soils. Our analysis of test results demonstrates that coupled biological and environmental factors within soil can be scaled (i.e., commensurably and analogously grouped)...
Article
From plate counts of the airborne microorganisms in the downwind dust plume of operating grass-seed combines, the mean source concentrations were calculated to be 6.4 x 10 and 4.7 x 10/m, respectively, potentially accounting for at least 41.9% of the bacteria and 35.1% of the fungi in the airshed in the Willamette Valley, Oregon.
Article
Cadmium inhibition of microorganisms was found to be bacterial and chemical species dependent. E. coli inhibition was a function of the cadmium-ion concentration irregardless of the presence of citrate, a chelator for cadmium that it could not metabolize. Whereas with a Pseudomonas sp. able to metabolize citrate, cadmium inhibition was a function o...
Article
A set of Douglas-fir needle litter microcosms was amended with cadmium, acid, a combination of both, or neither. After 2 weeks of incubation, bacterial colony counts were made of litter homogenates inoculated onto agar media containing an antibiotic (streptomycin, chloromycetin, ampicillin, or gentamicin), cadmium, both, or neither. In all microcos...
Article
In recent years, reuse of municipal waste water as the coolant in drift-producing cooling towers at electrical generating plants has become increasingly common. A hueristic model is presented that can be used to estimate the concentrations of viable airborne microbes in the drift from a wet cooling tower given the concentration of microbes in the c...
Article
Modification of the Pasquill atmospheric diffusion equations for estimating viable microbial airborne cell concentrations downwind form a continuous point source is presented. A graphical method is given to estimate the ground level cell concentration given (i) microbial death rate, (ii) mean wind speed, (iii) atmospheric stability class, (iv) down...
Article
This manuscript represents a detailed review of the literature pertaining to the interactions of and inter-relationships between atmospheric pollution and microorganisms. The review was composed in such a manner as to stress the effects of pollution upon microbial ecology. The first section presents a brief introduction of the general concepts of a...
Article
Vegetative cells of Serratia marcescens 8UK, Sarcina lutea, and spores of Bacillus subtilus var. niger were held in aerosols, with and without an urban concentration of CO (85 muliters per liter or ppm), for up to 6 hr at 15 C and a relative humidity (RH) of approximately 0, 25, 50, 75, and 95%. It was found that CO enhanced the death rate of S. ma...
Article
Vegetative cells of Serratia marcescens 8UK, Sarcina lutea, and spores of Bacillus subtilus var. niger were held in aerosols, with and without an urban concentration of CO (85 μliters per liter or ppm), for up to 6 hr at 15 C and a relative humidity (RH) of approximately 0, 25, 50, 75, and 95%. It was found that CO enhanced the death rate of S. mar...
Article
Aerosols of Serratia marcescens ATCC 274 were suspended in a 709L rotating drum at 20 ± 1 °C and high to mid-range relative humidities. At specified times after bacterial aerosolization, sulfur dioxide was added to concentrations of 2.5, or 5 mg/m. Viable cell decay rate constants, in control aerosols without added sulfur dioxide, increased rapidly...
Article
Can honey bees be used as collectors of atmospheric microbial agents of harm? Individual tethered honey bees were flown in a mini wind tunnel and exposed to a cloud of aerosolized bacterial spores (an Anthrax simulant). The bees adsorbed bacterial spores proportional to the measured electrostatic charge on the bee and to the aerosol exposure dose....
Article
Simulated droplet trajectories ofa polydispersed microbial aerosol ina laminar airflowregimen were compared withobserved dispersal patterns ofaerosolized Bacillus subtilis subsp. niger sporesinquasilaminar airflow. Simulated dispersal patterns couldbeexplained intermsofinitial droplet sizes andwhether the droplets evaporated toresidual aeroplankton...

Citations

... The specific species of virus may be more or less vulnerable to inactivation upon aerosolization and collection; in other words, some viruses are hardier than others (Verreault et al. 2008;Appert et al. 2012;Zuo et al. 2013;Ge et al. 2014). The method of aerosolization and the presence of protective factors (e.g., proteins, sugars, fomites) can impact virus viability (Israeli et al. 1994;Verreault et al. 2008;Zuo et al. 2014) by shielding the microorganism from inactivation. The environmental conditions to which the virus is exposed, such as ultraviolet light (UV, e.g., from the sun), temperature, and relative humidity, can significantly impact viability and is species dependent (Verreault et al. 2008;Posada et al. 2010;Gralton et al. 2011;Zhao et al. 2012). ...
... The net surface charge and hydrophobicity become significant as surrogates interact with interfaces (Gassilloud B, 2005). Typically, a lower hydrophobicity and lower isoelectric point allow an organism to travels larger distances as a result of less interaction with environmental interfaces (Cox, 1995), (Lighthart, 1994). The molecular structure and surface charges additionally impact on hydrophobicity. ...
... where the light source is mounted above the specimen) equipped with digital cameras which allow recording the image directly in a digital form. The automatic acquisition of images together with their analysis makes the examination time shorter and the use of several fluorochromes enables the simultaneous measurement of multiple parameters (Bartoszek and Rosowski, 2017;Després et al., 2012;Francisco et al., 1973;Harrison et al., 2005;Hernandez et al., 1999;Hobbie et al., 1977;Jensen et al., 1994;Karlsson and Malmberg, 1989;Kepner and Pratt, 1994;Pöhlker et al., 2011). Electron microscopy uses a beam of electrons instead of light. ...
... The atmosphere primarily assists as a transport medium for nutrients (Sajjad et al. 2022) and microorganisms rather than to serve as a reservoir for growth. Hence, the microbial composition in the air is greatly influenced by the geography and characteristics of the given environment, the nature of microorganisms and the transmission and transformation processes (Lighthart and Stetzenbach 1994a, b;Haas et al. 2013;Sharma Ghimire et al. 2019). The microbial concentration and community are governed mainly by the sources of microbial emissions, which could be either natural or anthropogenic, with meteorological influences such as season, temperature, relative humidity (RH) and time of day (Troutt and Levetin 2001;Haas et al. 2013). ...
... Fungal spores in the air are small enough for humans to inhale and cause health implications such as allergic reactions, tremors, lung inflammation, respiratory diseases, infectious diseases, kidney failure, and cancer (Andersen et al., 2009;Sorenson, 1999). Therefore, it is imperative to conduct studies on fungal spores to obtain data which can be utilized in preventing or mitigating human health implications in a timely manner. ...
... The concentration of microbes in the atmosphere increased with increasing temperature. However, Lighthart et al. [9] mentioned that when the temperature was too high, the ultraviolet radiation was strong, which, in turn, reduced the concentration of microorganisms in the atmosphere. Studies on the influence of humidity on microorganisms in the atmosphere found that high humidity was beneficial to the survival of the bacteria, and the release of spores was increased at low humidity [10]. ...
... with wind speed (Figure 2a). It has also been found that cultivable bacteria usually have a positive correlation with wind speed (Fahlgren et al., 2010;Lighthart et al., 2004;Marafie & Ashkanani, 1991). With winds greater than 5.4 m s À1 (i.e., exceeding Beaufort force 3, in which wave breaking can occur), the bacterial concentration was significantly higher than it was with wind speeds lower than 5.4 m s À1 (ANOVA P < .05). ...
... As a consequence, numerical quantification of microbial emissions, as well as investigations of the effects of living biological particles on the atmosphere and the water cycle have been limited to highly idealized scenarios. Lighthart and Kirilenko (1998) attempted to simulate summertime diurnal emission dynamics, but in their work net upward fluxes were a function of time and solar-radiation-dependent microbial death only. Population dynamics in the phyllosphere and atmospheric turbulence were not accounted for. ...
... In this study, composting plants based on swine manure were the subject of the investigation, whereas in the case of previous studies, the plants composted general waste, such as municipal solid waste and food waste. In addition, the fact that meteorological factors such as temperature, humidity, wind speed, and season, which affect the generation of airborne bacteria during the composting process, were different from each other at the time of measurement may be one of the reasons for variance [13][14][15]. ...
... Although the common route of transmission for enteric bacterial pathogens is direct contact or ingestion, there is evidence from animal studies suggesting that aerogenic routes are possible (Cornick and VuKhac 2008). Up to 42% of the bacterial loading in an air shed during harvest is thought to be caused by harvesting activities (Tong and Lighthart 2000). Emissions from degrading manure and livestock digestive processes produce air pollutants that often affect ambient air quality incommunities surrounding CAFOs (Heather, 2012). ...