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Airborne microorganisms, endotoxin, and (1-->3)-ß-D-glucan exposure in greenhouses and assessment of respiratory symptoms among workers.

Adhikari A; Gupta J; Wilkins JR III; Olds RL; Indugula R; Cho KJ; Li C; Yermakov M
Ann Occup Hyg 2011 Apr; 55(3):272-285
OBJECTIVES: Greenhouse operations are an important sector of the horticulture industry, also known as the Green Industry. The objectives of this study were (i) to investigate exposure levels to airborne culturable fungi, bacteria (total culturable bacteria and actinomycetes), endotoxin, and (1-->3)-ß-D-glucan in three Midwest greenhouses during summer and winter using multiple exposure assessment methods; (ii) characterize the load of microorganisms on greenhouse floors and determine potential microbial source strengths of the floors for aerosolizing microbial biocontaminants, and (iii) to estimate the prevalence of rhinitis, wheezing, asthma, and other respiratory symptoms/conditions among greenhouse workers. METHODS: Stationary inhalable aerosol samples were collected from each greenhouse using Button Inhalable Aerosol Samplers. Control samples were collected from offices and nearby outdoor locations. A microbial source strength tester was used to examine the aerosolization potential of microbial contaminants from greenhouse floors. Additionally, surface samples were collected by sterile cotton swabs. Temperature, relative humidity, and wind velocity were recorded. Airborne culturable fungi, bacteria, and actinomycetes were analyzed in the extracts from field samples by cultivation in nutrient agar media. Endotoxin and (1-->3)-ß-D-glucan in the extracts from field samples were analyzed by specific kinetic chromogenic Limulus amebocyte lysate assays. The prevalence of respiratory symptoms among greenhouse workers (n = 35) and control subjects (office workers; n = 14) was estimated with a standardized questionnaire. Results and CONCLUSIONS: The collected data indicate that workers employed in Midwest greenhouses may be exposed to elevated levels of inhalable culturable microorganisms (fungi and bacteria collectively on the order of 10(2)-10(5) CFU m(-3)), endotoxin (10(1)-10(3) EU m(-3)), and (1-->3)-ß-D-glucan (10(1)-10(2) ng m(-3)). Seasonal variations were observed for some bioaerosol components. The prevalence of self-reported respiratory symptoms was generally higher among greenhouse workers compared to controls; however, the differences were not statistically significant, likely due to the relatively low statistical power of the study.
Agricultural-workers; Agriculture; Humans; Men; Women; Age-groups; Microbiology; Air-quality; Airborne-particles; Exposure-levels; Exposure-limits; Pollution; Pollutants; Fungi; Microorganisms; Allergens; Bacteria; Bacterial-dusts; Endotoxins; Aerosol-particles; Aerosols; Respiration; Respiratory-irritants; Respiratory-system-disorders; Pulmonary-disorders; Pulmonary-system; Pulmonary-system-disorders; Workers; Work-environment; Allergic-reactions; Allergies; Author Keywords: allergens; bioaerosols; endotoxin; fungi; glucans; greenhouses; microorganisms; respiratory symptoms
Atin Adhikari, Department of Environmental Health, University of Cincinnati, Cincinnati, OH 45267
Publication Date
Document Type
Journal Article
Email Address
Funding Type
Fiscal Year
Identifying No.
Grant-Number-R03-OH-009241; B01182012
Issue of Publication
Source Name
Annals of Occupational Hygiene
Performing Organization
University of Cincinnati
Page last reviewed: April 9, 2021
Content source: National Institute for Occupational Safety and Health Education and Information Division