Bioaerosol Components Research Articles

Upper airway inflammation in waste handlers exposed to bioaerosols

Aims: To examine work associated upper airway inflammation in 31 waste handlers, and to correlate these findings with personally monitored exposure to different bioaerosol components. Methods: Cell differentials, interleukin 8...

Methods for quantitative assessment of airborne levels of noninfectious microorganisms in highly contaminated work environments.

Exposure to high airborne levels of noninfectious microorganisms is recognized as a cause of respiratory symptoms and disease among workers handling biological materials, such as farmers, sawmill workers, and workers handling municipal waste and fuel chips. Risk assessment is difficult because occupational exposure limits for noninfectious microorganisms have not been established. Many different methods are used for the measurement of airborne microorganisms, which are based on impaction, impingement, or filtration. Samples can be analyzed by methods that are culture-based or nonculture-based and that may estimate different microbial entities: culturable microorganisms by culture-based methods, microbial cells by microscopic methods, and microbial constituents and products by chemical, biochemical and immunochemical methods. Sources of errors and validation studies of these methods are reviewed and methods are evaluated for exposure assessment in epidemiological studies and for future compliance testing. At present it is not clear which microbial bioaerosol components should be assessed. Culture-based methods are probably not satisfactory because nonviable microorganisms and microbial constituents and products also may cause health effects. Culture-based methods are poor surrogates for nonculture-based methods and have poor precision. However, identification of microorganisms is most readily performed by culture-based methods. Filter sampling is preferred for personal exposure measurements because filters can be analyzed by a variety of nonculture-based methods, and filter sampling may be adapted to recently adopted criteria for health-related size fractions.

Methods for Quantitative Assessment of Airborne Levels of Noninfectious Microorganisms in Highly Contaminated Work Environments

Exposure to high airborne levels of noninfectious microorganisms is recognized as a cause of respiratory symptoms and disease among workers handling biological materials, such as farmers, sawmill workers, and workers handling municipal waste and fuel chips. Risk assessment is difficult because occupational exposure limits for noninfectious microorganisms have not been established. Many different methods are used for the measurement of airborne microorganisms, which are based on impaction, impingement, or filtration. Samples can be analyzed by methods that are culture-based or nonculture-based and that may estimate different microbial entities: culturable microorganisms by culture-based methods, microbial cells by microscopic methods, and microbial constituents and products by chemical, biochemical and immunochemical methods. Sources of errors and validation studies of these methods are reviewed and methods are evaluated for exposure assessment in epidemiological studies and for future compliance testing. At present it is not clear which microbial bioaerosol components should be assessed. Culture-based methods are probably not satisfactory because nonviable microorganisms and microbial constituents and products also may cause health effects. Culture-based methods are poor surrogates for nonculture-based methods and have poor precision. However, identification of microorganisms is most readily performed by culture-based methods. Filter sampling is preferred for personal exposure measurements because filters can be analyzed by a variety of nonculture-based methods, and filter sampling may be adapted to recently adopted criteria for health-related size fractions.

Measurement methods and strategies for non-infectious microbial components in bioaerosols at the workplace.

Exposure to micro-organisms can be measured by different methods. Traditionally, viable methods and light microscopy have been used for detection of micro-organisms. Most viable methods measure micro-organisms that are able to grow in culture, and these methods are also common for the identification of micro-organisms. More recently, non-viable methods have been developed for the measurement of bioaerosol components originating from micro-organisms that are based on microscopic techniques, bioassays, immunoassays and chemical methods. These methods are important for the assessment of exposure to bioaerosols in work environments as non-infectious micro-organisms and microbial components may cause allergic and toxic reactions independent of viability. It is not clear to what extent micro-organisms should be identified because exposure-response data are limited and many different micro-organisms and microbial components may cause similar health effects. Viable methods have also been used in indoor environments for the detection of specific organisms as markers of indoor growth of micro-organisms. At present, the validity of measurement methods can only be assessed by comparative laboratory and field studies because standard materials of microbial bioaerosol components are not available. Systematic errors may occur especially when results obtained by different methods are compared. Differences between laboratories that use the same methods may also occur as quality assurance schemes of analytical methods for bioaerosol components do not exist. Measurement methods may also have poor precision, especially the viable methods. It therefore seems difficult to meet the criteria for accuracy of measurement methods of workplace exposure that have recently been adopted by the CEN. Risk assessment is limited by the lack of generally accepted reference values or guidelines for microbial bioaerosol components. The cost of measurements of exposure to microbial bioaerosol components may be high owing to expensive analyses and highly variable exposure levels. The use of qualitative indicators of microbial growth, recording of health effects, specific immunoglobulin G antibody levels to prevalent species in serum of exposed workers and stratified sampling may help to reduce the costs of exposure assessment. An example of a combined strategy for assessment of health risks from handling mouldy timber is shown.