Biomedical subjects

Michael L Muilenberg

Publications and source records attributed to Michael L Muilenberg.

9 recordsLinked to original sources

PubMed2007

Characterization of airborne molds, endotoxins, and glucans in homes in New Orleans after Hurricanes Katrina and Rita.

In August and September 2005, Hurricanes Katrina and Rita caused breeches in the New Orleans, LA, levee system, resulting in catastrophic flooding. The city remained flooded for several weeks, leading to extraordinary mold growth in homes. To characterize the potential risks of mold exposures, we measured airborne molds and markers of molds and bacteria in New Orleans area homes. In October 2005, we collected air samples from 5 mildly water-damaged houses, 15 moderately to heavily water-damaged houses, and 11 outdoor locations. The air filters were analyzed for culturable fungi, spores, (1-->3,1-->6)-beta-D-glucans, and endotoxins. Culturable fungi were significantly higher in the moderately/heavily water-damaged houses (geometric mean=67,000 CFU/m3) than in the mildly water-damaged houses (geometric mean=3,700 CFU/m3) (P=0.02). The predominant molds found were Aspergillus niger, Penicillium spp., Trichoderma, and Paecilomyces. The indoor and outdoor geometric means for endotoxins were 22.3 endotoxin units (EU)/m3 and 10.5 EU/m3, respectively, and for (1-->3,1-->6)-beta-D-glucans were 1.7 microg/m3 and 0.9 microg/m3, respectively. In the moderately/heavily water-damaged houses, the geometric means were 31.3 EU/m3 for endotoxins and 1.8 microg/m3 for (1-->3,1-->6)-beta-D-glucans. Molds, endotoxins, and fungal glucans were detected in the environment after Hurricanes Katrina and Rita in New Orleans at concentrations that have been associated with health effects. The species and concentrations were different from those previously reported for non-water-damaged buildings in the southeastern United States.

Air Microbiology↗

PubMed2006

Interaction of the onset of spring and elevated atmospheric CO2 on ragweed (Ambrosia artemisiifolia L.) pollen production.

Increasing atmospheric carbon dioxide is responsible for climate changes that are having widespread effects on biological systems. One of the clearest changes is earlier onset of spring and lengthening of the growing season. We designed the present study to examine the interactive effects of timing of dormancy release of seeds with low and high atmospheric CO2 on biomass, reproduction, and phenology in ragweed plants (Ambrosia artemisiifolia L.), which produce highly allergenic pollen. We released ragweed seeds from dormancy at three 15-day intervals and grew plants in climate-controlled glass-houses at either ambient or 700-ppm CO2 concentrations, placing open-top bags over influorescences to capture pollen. Measurements of plant height and weight; inflorescence number, weight, and length; and days to anthesis and anthesis date were made on each plant, and whole-plant pollen productivity was estimated from an allometric-based model. Timing and CO2 interacted to influence pollen production. At ambient CO2 levels, the earlier cohort acquired a greater biomass, a higher average weight per inflorescence, and a larger number of influorescences; flowered earlier; and had 54.8% greater pollen production than did the latest cohort. At high CO2 levels, plants showed greater biomass and reproductive effort compared with those in ambient CO2 but only for later cohorts. In the early cohort, pollen production was similar under ambient and high CO2, but in the middle and late cohorts, high CO2 increased pollen production by 32% and 55%, respectively, compared with ambient CO2 levels. Overall, ragweed pollen production can be expected to increase significantly under predicted future climate conditions.

Ambrosia↗

PubMed2006

Mold and endotoxin levels in the aftermath of Hurricane Katrina: a pilot project of homes in New Orleans undergoing renovation.

BACKGROUND: After Hurricane Katrina, many New Orleans homes remained flooded for weeks, promoting heavy microbial growth. OBJECTIVES: A small demonstration project was conducted November 2005-January 2006 aiming to recommend safe remediation techniques and safe levels of worker protection, and to characterize airborne mold and endotoxin throughout cleanup. METHODS: Three houses with floodwater lines between 0.3 and 2 m underwent intervention, including disposal of damaged furnishings and drywall, cleaning surfaces, drying remaining structure, and treatment with a biostatic agent. We measured indoor and outdoor bioaerosols before, during, and after intervention. Samples were analyzed for fungi [culture, spore analysis, polymerase chain reaction (PCR)] and endotoxin. In one house, realtime particle counts were also assessed, and respirator-efficiency testing was performed to establish workplace protection factors (WPF). RESULTS: At baseline, culturable mold ranged from 22,000 to 515,000 colony-forming units/m3, spore counts ranged from 82,000 to 630,000 spores/m3, and endotoxin ranged from 17 to 139 endotoxin units/m3. Culture, spore analysis, and PCR indicated that Penicillium, Aspergillus, and Paecilomyces predominated. After intervention, levels of mold and endotoxin were generally lower (sometimes, orders of magnitude). The average WPF against fungal spores for elastomeric respirators was higher than for the N95 respirators. CONCLUSIONS: During baseline and intervention, mold and endotoxin levels were similar to those found in agricultural environments. We strongly recommend that those entering, cleaning, and repairing flood-damaged homes wear respirators at least as protective as elastomeric respirators. Recommendations based on this demonstration will benefit those involved in the current cleanup activities and will inform efforts to respond to future disasters.

Air Microbiology↗

PubMed2005

Fungal levels in the home and allergic rhinitis by 5 years of age.

Studies have repeatedly demonstrated that sensitization to fungi, such as Alternaria, is strongly associated with allergic rhinitis and asthma in children. However, the role of exposure to fungi in the development of childhood allergic rhinitis is poorly understood. In a prospective birth cohort of 405 children of asthmatic/allergic parents from metropolitan Boston, Massachusetts, we examined in-home high fungal concentrations (> 90th percentile) measured once within the first 3 months of life as predictors of doctor-diagnosed allergic rhinitis in the first 5 years of life. In multivariate Cox regression analyses, predictors of allergic rhinitis included high levels of dust-borne Aspergillus [hazard ratio (HR) = 3.27; 95% confidence interval (CI), 1.50-7.14], Aureobasidium (HR = 3.04; 95% CI, 1.33-6.93), and yeasts (HR = 2.67; 95% CI, 1.26-5.66). The factors controlled for in these analyses included water damage or mild or mildew in the building during the first year of the child's life, any lower respiratory tract infection in the first year, male sex, African-American race, fall date of birth, and maternal IgE to Alternaria > 0.35 U/mL. Dust-borne Alternaria and nonsporulating and total fungi were also predictors of allergic rhinitis in models excluding other fungi but adjusting for all of the potential confounders listed above. High measured fungal concentrations and reports of water damage, mold, or mildew in homes may predispose children with a family history of asthma or allergy to the development of allergic rhinitis.

Boston↗

PubMed2004

Dog allergen (Can f 1) and cat allergen (Fel d 1) in US homes: results from the National Survey of Lead and Allergens in Housing.

BACKGROUND: Exposures to dog and cat allergens are believed to play important roles in the etiology of asthma; however, the levels of these allergens have never been assessed in a representative sample of US homes. OBJECTIVE: The objective of this study was to estimate and characterize exposures to Can f 1 (dog allergen) and Fel d 1 (cat allergen) in US homes. METHODS: Data were obtained from the National Survey of Lead and Allergens in Housing, a nationally representative survey of 831 US homes. Vacuumed-collected dust samples from the bed, bedroom floor, living room floor, and living room sofa were analyzed for concentrations of Can f 1 and Fel d 1 (micrograms of allergen per gram of dust). RESULTS: Although a dog or cat had lived in only 49.1% of homes in the previous 6 months, Can f 1 and Fel d 1 were detected in 100% and 99.9% of homes, respectively. Averaged over the sampled sites, geometric mean concentrations (microg/g) were 4.69 for Can f 1 and 4.73 for Fel d 1. Among homes with an indoor dog and cat, respectively, geometric mean concentrations were 69 for Can f 1 and 200 for Fel d 1. Among homes without the indoor pet, geometric mean concentrations were above 1.0. The independent predictors of elevated concentrations in homes without pets were all demographic variables that were also linked to a higher prevalence of pet ownership. CONCLUSIONS: Can f 1 and Fel d 1 are universally present in US homes. Levels that have been associated with an increased risk of allergic sensitization were found even in homes without pets. Because of the transportability of these allergens on clothing, elevated levels in homes without pets, particularly among demographic groups in which pet ownership is more prevalent, implicate the community as an important source of these pet allergens.

Allergens↗

PubMed2003

Sampling devices.

A number of commonly used samplers are presented in this article. Many samplers have not been discussed because they are used for specific purposes or are considered research tools. Air sampling for microbes may seem like a simple proposal, yet to develop and implement a well-thought out plan that answers questions or hypotheses with a high level of reliability is often a difficult and expensive undertaking. Sampler selection is only one step in this process. The information given in this article, along with the other resources listed, should aid in setting up a useful bioaerosol sampling plan.

Aerosols↗

PubMed2003

House dust mite allergen in US beds: results from the First National Survey of Lead and Allergens in Housing.

BACKGROUND: Although exposure to house dust mite allergen is a major risk factor for allergic sensitization and asthma, nationwide estimates of dust mite allergen levels in US homes have not been reported. OBJECTIVE: The purpose of this study was to estimate the prevalence of dust mite allergen in beds of US homes and to identify predictors of dust mite allergen concentration. METHODS: Data were obtained from the first National Survey of Lead and Allergens in Housing, a cross-sectional survey of 831 permanently occupied noninstitutional housing units that permitted resident children. Dust mite allergen concentration (Der f 1 plus Der p 1) was determined from a dust sample collected from a bed. The percentages of homes with concentrations at or greater than detection, 2.0 microg/g bed dust, and 10.0 microg/g bed dust were estimated. Independent predictors of allergen concentration were assessed with multivariable linear regression. RESULTS: The percentages of US homes with dust mite allergen concentrations at or greater than detection, 2.0 microg/g, and 10.0 microg/g were 84.2% (SE, 1.73), 46.2% (SE, 2.0), and 24.2% (SE, 2.1), respectively. Independent predictors of higher levels were older homes, non-West census regions, single-family homes, no resident children, lower household income, heating sources other than forced air, musty or mildew odor, and higher bedroom humidity. CONCLUSION: Most US homes have detectable levels of dust mite allergen in a bed. Levels previously associated with allergic sensitization and asthma are common in US bedrooms. Predictors can be used to identify conditions under which homes are more likely to have increased dust mite allergen levels.

Allergens↗

PubMed2002

Effect of sampling time on the culturability of airborne fungi and bacteria sampled by filtration.

Air sampling of bioaerosols by filtration may be preferable for many epidemiological studies because the methods can be used to collect personal samples for a full work-shift. There is some concern, however, that the viability of fungal spores and bacterial cells might be compromised by sampling for as long as a full shift. This study was designed to determine the effect of sampling up to 6 h on the viability (measured by culture) of airborne fungi and bacteria at composting facilities. Six side-by-side samples were collected in two locations at each of three composting facilities for 1 h at 2 l/m on polycarbonate filters. Two samples in each set were then capped while clean, HEPA-filtered air was drawn across two others for an additional 2 h and across the last two for an additional 5 h. Filters were washed and the samples were analyzed for culturable bacteria and fungi, and for total bacteria and fungi by microscopic counting. Concentrations ranged from 1.7 x 10(3) to 6.2 x 10(7) c.f.u./m3 of culturable fungi and 1.17 x 10(4) to 1.0 x 10(6) c.f.u./m3 of culturable bacteria. In linear models that included duration of sampling, location, and the interaction of location and sample duration, neither sample duration nor the interaction term were significant predictors of the logs of the concentrations of culturable fungi or bacteria or of the ratio of the logs of the culturable concentrations to total concentrations for fungi or bacteria. This suggests that increased sampling time does not affect the viability of the organisms commonly found in the air at composting facilities.

Air Microbiology↗

PubMed2002

First National Survey of Lead and Allergens in Housing: survey design and methods for the allergen and endotoxin components.

From July 1998 to August 1999, the U.S. Department of Housing and Urban Development and the National Institute of Environmental Health Sciences conducted the first National Survey of Lead and Allergens in Housing. The purpose of the survey was to assess children's potential household exposure to lead, allergens, and bacterial endotoxins. We surveyed a sample of 831 homes, representing 96 million permanently occupied, noninstitutional housing units that permit resident children. We administered questionnaires to household members, made home observations, and took environmental samples. This article provides general background information on the survey, an overview of the survey design, and a description of the data collection and laboratory methods pertaining to the allergen and endotoxin components. We collected dust samples from a bed, the bedroom floor, a sofa or chair, the living room floor, the kitchen floor, and a basement floor and analyzed them for cockroach allergen Bla g 1, the dust mite allergens Der f 1 and Der p 1, the cat allergen Fel d 1, the dog allergen Can f 1, the rodent allergens Rat n 1 and mouse urinary protein, allergens of the fungus Alternaria alternata, and endotoxin. This article provides the essential context for subsequent reports that will describe the prevalence of allergens and endotoxin in U.S. households, their distribution by various housing characteristics, and their associations with allergic diseases such as asthma and rhinitis.

Allergens↗