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J M Macher

Publications and source records attributed to J M Macher.

18 recordsLinked to original sources
PubMed2005

Concentrations of airborne culturable bacteria in 100 large US office buildings from the BASE study.

UNLABELLED: This paper presents summary statistics of airborne culturable bacteria from the US Environmental Protection Agency Building Assessment Survey and Evaluation (BASE) study. Air samples were collected with single-stage, multiple-hole, agar impactors in 100 large office buildings in 1994-1998 to obtain normative data on indoor environmental quality. Bacterial concentrations were compared by incubation temperature, location, season, and climate zone. Forty-one percent of the samples were below the 2- or 5-min detection limits (18 or 7 CFU/m3, respectively) but less than 1% were overgrown. Mesophilic bacteria (30 degrees C) accounted for >95% of culturable bacteria, both indoors and outdoors. Average concentrations were higher outdoors, except for Gram-positive cocci, which were the only group that were significantly higher indoors (39 vs. 24 CFU/m3), and Gram-negative cocci, for which both concentrations were low and the difference were not significant. Outdoor concentrations of culturable bacteria were somewhat higher in winter (194 vs.165 CFU/m3), and the two dominant outdoor groups were unknown bacteria and Gram-positive rods. Conversely, indoor concentrations were significantly higher in summer (116 vs. 87 CFU/m3), consisting primarily of unknown bacteria and Gram-positive cocci. Bacterial concentrations were within the ranges reported in previous studies of non-problem buildings, and the extreme aggregated indoor concentrations (e.g. the 90th percentile, 175 CFU/m3) of these 100 representative buildings may serve as upper bounds to develop interpretation guidelines for office environments and similar non-manufacturing workplaces in various climate zones. PRACTICAL IMPLICATIONS: The Building Assessment Survey and Evaluation (BASE) study was one of the most comprehensive investigations of indoor environmental quality in which a standardized protocol was used to measure bioaerosols in 100 typical US office buildings. The information on the indoor and outdoor concentrations of airborne bacteria in different climate zones during the heating and cooling seasons has expanded the baseline data available for interpretation of measurements from building investigations. With suggested refinements, the BASE protocol may serve as a guide for future studies of bioaerosol concentrations, building characteristics, and occupant perceptions of the indoor environment.

Air Microbiology↗
PubMed2005

Concentrations of cat and dust-mite allergens in dust samples from 92 large US office buildings from the BASE Study.

UNLABELLED: The concentrations of cat (Fel d1) and dust-mite (Der f1 and Der p1) allergens were measured in 92 large office buildings in the US Environmental Protection Agency's Building Assessment Survey and Evaluation (BASE) Study (251 dust samples; one to four samples per building). Fel d1 was detected in almost all buildings and samples (91 buildings, 99%; 235 samples, 94%; range: <0.01-19 microg/g; median: 0.3 microg/g). Cat allergen exceeded 1 microg/g (a lower symptom threshold) in 56 samples (22%) from 45 buildings, but exceeded 8 microg/g (a sensitization threshold) in only two samples (1%) from two buildings. Der f1 or Der p1 was found in approximately half of all buildings and samples (63 and 70% of buildings; 45 and 51% of samples; range: <0.01-53 microg/g and <0.01-25 microg/g; median: <0.02 and 0.03 microg/g, respectively). Mite allergen exceeded 2 microg/g (a sensitization threshold) in seven samples (3%) from five buildings and exceeded 10 microg/g (a symptom threshold) in three samples (1%) from three buildings. Fel d1 concentration was significantly higher in samples collected in summer (June to September, 48 buildings), but cat allergen was not correlated with either mite allergen. Der f1, but not Der p1, concentration tended to be higher in samples collected in winter (December to April, 44 buildings), and the two mite allergens were significantly correlated only in winter. Cat and mite allergens were detected in 78% of representative US office buildings, but the concentrations seldom exceeded levels associated with sensitization or symptom provocation. PRACTICAL IMPLICATIONS: The information on the concentrations of cat and dust-mite allergens in representative large US offices has expanded the baseline data available for interpretation of measurements from other building investigations. With suggested refinements, the BASE protocol for measurement of allergen concentrations in dust samples may serve as a guide to future studies of building characteristics, bioaerosol concentrations, and occupant perceptions of the indoor environment.

Air Microbiology↗
PubMed2001

Review of methods to collect settled dust and isolate culturable microorganisms.

Examination of settled dust is often included in investigations of indoor environments to identify the types and concentrations of particles to which building occupants may be exposed. Fungi and bacteria are among the many components in dust that have been studied. Isolation by culture is an established method that is used widely to quantify and identify microorganisms in environmental samples. However, no standard procedures for culturing fungi or bacteria from dust have been adopted widely to ensure the validity of comparing findings from different studies. This paper reviews methods various researchers have used to study surface particles and to isolate culturable microorganisms from dust. Factors that were found to differ included the method of sample collection, the ways dust was prepared for inoculation onto growth media, and the culture media chosen for specific categories of agents. The need for reference methods in environmental microbiology for use in the assessment of indoor environmental quality is discussed.

Air Pollution, Indoor↗
PubMed2001

Evaluation of a procedure to isolate culturable microorganisms from carpet dust.

Details of a method to isolate culturable bacteria and fungi from carpet dust were evaluated to isolate the greatest numbers of these agents. Four broad groups were evaluated: mesophilic and thermophilic bacteria and moderately hydrophilic and xerophilic fungi. Features studied included: 1) mixing time; 2) addition of glass beads; 3) length of time dust settled before suspensions were plated; 4) relative concentrations of microorganisms in the fibrous and fine dust fractions; and 5) storage temperature and period. The findings are preliminary because of the small number of samples, but a votexing time of at least 2 min with glass beads gave the best results in terms of the highest estimate of the concentration of culturable bacteria or fungi. Microorganisms were retrievable-from the upper portion of a suspending liquid for at least 30 min with little detectable change in concentration. Both bacteria and fungi were more abundant in the fine than the fibrous dust fraction. No significant losses were observed for samples stored up to 25 days at 5 degrees C or 25 degrees C. This procedure optimized measurement of total concentration, but may not identify the range of genera and species in dust if microorganisms present in small numbers and as single units are underrepresented relative to those in clusters and aggregates.

Air Pollution, Indoor↗
PubMed1996

Effectiveness of in-room air filtration and dilution ventilation for tuberculosis infection control.

Tuberculosis (TB) is a public health problem that may pose substantial risks to health care workers and others. TB infection occurs by inhalation of airborne bacteria emitted by persons with active disease. We experimentally evaluated the effectiveness of in-room air filtration systems, specifically portable air filters (PAFs) and ceiling-mounted air filters (CMAFs), in conjunction with dilution ventilation, for controlling TB exposure in high-risk settings. For each experiment, a test aerosol was continuously generated and released into a full-sized room. With the in-room air filter and room ventilation system operating, time-averaged airborne particle concentrations were measured at several points. The effectiveness of in-room air filtration plus ventilation was determined by comparing particle concentrations with and without device operation. The four PAFs and three CMAFs we evaluated reduced room-average particle concentrations, typically by 30% to 90%, relative to a baseline scenario with two air-changes per hour of ventilation (outside air) only. Increasing the rate of air flow recirculating through the filter and/or air flow from the ventilation did not always increase effectiveness. Concentrations were generally higher near the emission source than elsewhere in the room. Both the air flow configuration of the filter and its placement within the room were important, influencing room air flow patterns and the spatial distribution of concentrations. Air filters containing efficient, but non-high efficiency particulate air (HEPA) filter media were as effective as air filters containing HEPA filter media.

Filtration↗
PubMed1995

Factors affecting microbiological colony count accuracy for bioaerosol sampling and analysis.

The effects of the following variables on the occurrence of colony masking (the indistinguishable merging or overlap of sufficiently close colonies) were evaluated experimentally using the bacterium Bacillus subtilis: spore density on a collection surface, concentration of nutrients in the culture medium, sample incubation time, and ability of an observation system to distinguish overlapped colonies. Increasing spore surface density and incubation time increased colony masking, whereas lowering nutrient concentration decreased colony diameter and, therefore, masking but also limited spore germination and growth. Overall, full-strength medium was best for accurate counting of early microcolonies examined with the aid of a microscope, whereas half- or quarter-strength medium was better for counting older readily observable macrocolonies. Masking bias was determined for varying spore surface densities and colony diameters and was applied to two widely used slit-to-agar bioaerosol impactors. Appropriate collection times have been determined for these samplers to minimize colony masking for expected bioaerosol concentrations. It was found, for example, that 6-min samples collected from an environment with an air concentration of 10(3) CFU m-3 would result in colony surface densities, for 3-mm colonies, of 1.5 and 3.9 microorganisms cm-2 for the two samplers with respective masking biases of < 10% and < 20%.

Aerosols↗
PubMed1994

Evaluation of counting error due to colony masking in bioaerosol sampling.

Colony counting error due to indistinguishable colony overlap (i.e., masking) was evaluated theoretically and experimentally. A theoretical model to predict colony masking was used to determine colony counting efficiency by Monte Carlo computer simulation of microorganism collection and development into CFU. The computer simulation was verified experimentally by collecting aerosolized Bacillus subtilis spores and examining micro- and macroscopic colonies. Colony counting efficiency decreased (i) with increasing density of collected culturable microorganisms, (ii) with increasing colony size, and (iii) with decreasing ability of an observation system to distinguish adjacent colonies as separate units. Counting efficiency for 2-mm colonies, at optimal resolution, decreased from 98 to 85% when colony density increased from 1 to 10 microorganisms cm-2, in contrast to an efficiency decrease from 90 to 45% for 5-mm colonies. No statistically significant difference (alpha = 0.05) between experimental and theoretical results was found when colony shape was used to estimate the number of individual colonies in a CFU. Experimental colony counts were 1.2 times simulation estimates when colony shape was not considered, because of nonuniformity of actual colony size and the better discrimination ability of the human eye relative to the model. Colony surface densities associated with high counting accuracy were compared with recommended upper plate count limits and found to depend on colony size and an observation system's ability to identify overlapped colonies. Correction factors were developed to estimate the actual number of collected microorganisms from observed colony counts.(ABSTRACT TRUNCATED AT 250 WORDS)

Aerosols↗
PubMed1991

Public inquiries about indoor air quality in California.

To identify the indoor air quality issues about which Californians most often sought advice from a health department or a public information agency and to evaluate how well these agencies met the public's needs, members of the California Interagency Working Group (IWG) on Indoor Air Quality kept records of inquiries they received over a 30-month period from mid-1985 through 1987. Members of the IWG answered calls from residents of a least 49 of California's 58 counties. IWG members received more public inquiries about residences than about offices, educational institutions, commercial buildings, or medical facilities. However, each call about a residence probably represented fewer people at risk of exposure to a real or a potential problem than did calls about other types of buildings. Homeowners themselves asked the majority of the questions about residences, whereas a large number of the inquiries about office buildings were made, not by affected office workers, but by building managers, contractors, consultants, or company health and safety officers. The leading topics of concern in the residences were asbestos, chemical and biological contamination, and radon. In offices, chemical contamination, the ventilation system, biological contamination, asbestos, and tobacco smoke were the most frequently mentioned sources of problems. Callers often reported experiencing headaches, allergy symptoms, nose or throat irritation, and respiratory tract problems in connection with their complaints. IWG members directed a third of the calls elsewhere, of which half were referred to consultants or testing laboratories. The IWG's experience in the State of California could help other health departments prepare to face the public's increasing concern about indoor air pollution.

Air Pollution, Indoor↗
PubMed1989

Positive-hole correction of multiple-jet impactors for collecting viable microorganisms.

Multiple-jet impactors, typically with 200 or 400 holes, are used widely for collecting aerosols of living bacteria and fungi. In this type of impactor, the air jets impinge directly onto nutrient agar in a petri dish which is incubated after sampling until collected cells multiply into colonies. The observed number of colonies can be adjusted for the probability that more than one viable particle was collected through a sampling hole and merged with other microorganisms at an impaction site to produce a single colony. A "positive-hole" correction table has been published for a 400-hole impactor, but none has been produced previously for the 200-hole impactor. The expected number of sampled particles required to fill each of 1 through 200 and 1 through 400 impaction sites and the standard deviations of these values were calculated from probability theory. The results were compared with a Monte Carlo simulation. By using correction tables (which include the standard deviation of an expected value) an investigator can report the most probable viable particle count and a 95% confidence interval (mean +/- 2 standard deviations). The range of collected particles that could have produced an observed number of colonies increases as the number of collected particles increases, and investigators should acknowledge the uncertainty associated with adjusted counts. It is advisable to use an impactor with the greatest practical number of sampling holes because this decreases the likelihood that multiple particles are deposited at the impaction sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Air Microbiology↗
PubMed1987

Personal size-separating impactor for sampling microbiological aerosols.

A commercially-available personal impactor was altered to sample viable microorganisms onto a semisolid, moist, gelatin medium rather than onto a stainless steel or filter surface. The Marple personal cascade impactor is an eight-stage sampler with predicted cut-offs of 20, 15, 10, 6, 3.5, 2, 1, and 0.61 microns for stages one to eight, at a flow rate of 2 L/min. The possibility was examined that using trays containing a small amount of gelatin medium in place of the thin, flat filters of the original design would alter the impactor's performance. A polydisperse aerosol of di-2-ethylhexyl phthalate (DEHP or DOP) was sampled directly into an aerodynamic particle sizer and through a stage of the personal impactor. The aerosol particles penetrating the tested stage were sized and counted, and the counts compared with those in the total aerosol. With a Mylar medium filter as the collecting substrate, the measured particle cut-offs (D50) for stages four to seven were 5.2, 3.4, 1.4, and 1.0 microns. With a tray containing gelatin as the collecting substrate, the D50 were 5.9, 4.0, 1.6, and 1.0 microns. The size separation of the personal sampler for ambient bacterial and fungal aerosols compared well with that of the Andersen microbiological impactor. The use of a moist collecting surface, compared to a dry surface, can be expected to enhance recovery of viable airborne microorganisms sensitive to dehydration.

Aerosols↗
PubMed1984

Personal air samplers for measuring occupational exposures to biological hazards.

Microbiological air samplers, designed to be worn as personal samplers, were evaluated for studying occupational exposures to aerosols of infectious and allergenic materials. Gelatin filter media, an impinger sampler, and spiral and cascade impactors were tested for collection efficiency for small (less than or equal to 2 microns) latex spheres and for recovery of bacterial aerosols. Only 20% of an aerosol of 0.8 micron latex particles passed through the impinger uncollected, while recovery of bacteria equalled or exceeded collection in an all-glass impinger. Gelatin filters matched the collection efficiency of membrane filters, but were unsatisfactory for the isolation of bacteria sensitive to dehydration. The spiral sampler and the cascade impactor provide information on the size distribution of collected particles, although, at present, collection efficiencies for very small particles are too low for rigorously quantitative studies. Methods of collection, and sampling strategies for biological aerosols are similar to those used for measuring exposures of workers to chemical and mineral aerosols; however, preparation of samples and identification of isolates may have to be referred to experts in the fields of bacteriology, virology, and mycology.

Aerosols↗
PubMed1984

Effects of airflow rates and operator activity on containment of bacterial aerosols in a class II safety cabinet.

Biological safety cabinets are frequently relied upon to provide sterile work environments in which hazardous microorganisms can be safely handled. Verification of correct airstream velocities does not, by itself, ensure that adequate protection will be achieved under all users. Instead, the concentration of microorganisms in a cabinet operator's breathing zone must be measured during typical cabinet use conditions to determine whether the exposure is below acceptable limits. In this study, cabinet operator exposures were measured with a personal air sampler. Bacterial spores were released inside a cabinet as a uniform challenge aerosol, and the number of escaping spores was measured for several cabinet arrangements during a number of typical operations. The following were studied to determine their effects on aerosol containment: inflow air velocity, size of access opening, type of operator movements, location of operator's hands, and pace of activity. Other experiments examined differences in aerosol containment for eight typical microbiology operations when performed by six operators who covered a range of body heights and volumes.

Aerosols↗
PubMedDate not supplied

A two-year study of microbiological indoor air quality in a new apartment.

Concentrations and types of bacteria and fungi in the air and on surfaces were measured in a new, one-bedroom apartment before occupancy and at 3-mo intervals thereafter for 2 y. Air samples were collected with a single-stage impactor at two locations in the kitchen, living room, bedroom, bathroom, and outdoors. Even though damp surfaces supported large populations of bacteria and yeasts, the air concentrations in the kitchen and bathroom were similar to those in other rooms. No changes in concentrations or types of microbiological contamination were observed between the first and second years of occupancy, but elevated outdoor humidity, lower air temperature, and winds from the northeast were associated with higher bacterial and fungal air concentrations. The median air concentrations of bacteria were 98 cfu/m3 (95% confidence interval 26-372 cfu/m3) indoors and 101 cfu/m3 (28-364 cfu/m3) outdoors. The median air concentrations of fungi were 198 cfu/m3 (58-673 cfu/m3) indoors and 362 cfu/m3 (113-1158 cfu/m3) outdoors. This information established useful baseline data against which measurements in neighboring complaint residences could be compared.

Air Microbiology↗
PubMedDate not supplied

Protocol for the comprehensive evaluation of building-associated illness.

A protocol is outlined that represents a multidisciplinary approach to investigations of problem buildings and building-associated illness. The protocol includes methods to obtain background information on a problem and to conduct the initial site visit. The initial visit often leads to a more extensive medical investigation and environmental evaluation, as covered in this paper. The protocol also describes how the results of medical and environmental evaluations might best be analyzed to make ways to correct problems.

Air Conditioning↗