Study On Personal Exposure To Airborne Microbes And Risk Assessment Of Their Exposure In Residential Environments And Working Environments

Human spend up to 90%of their time in residential and working environments.Bioaerosols in residential and working environments are a cause for concern as it highly related to human health.Bioaerosols are the particles containing both living and non-living components,such as bacteria,fungi,pollen and virus.Inhalation of bioaerosols can cause a series of human health effects.For example,long time exposure to fungal and bacterial aerosols may cause respiratory diseases,asthma,allergies,etc.Some large-particle bacterial aerosols entering the human body through the esophagus are potential factors that cause intestinal diseases.Hence,it is very important to detect and identify the bioaerosol exposure in residential and working environment,and relate this to evaluate the health risk assessment.This study took the air samples from residential environments and 3 different working environments.Cultivable method,q PCR method and LAL method were used to study the microbal concentration,composition and particle size distribution in these envrionments.Combined these results with different risk asssessment methods to evaluate the huamn exposure risk.The main conclusions of this study are as follows:(1)Fungal fragments were both detected in the PM₁samples and the GSP samples.The total concentration of fungi as measured using universal fungal primers in GSP samples was significantly higher than that in PM₁samples(p<0.05).A significant effect of season was found in regards to the fungal?-diversity in the PM₁(p=0.001)and GSP samples(p=0.017),but no significant difference in?-diversity was found between the 5 homes(p>0.05).This is the first study to show that Alnus/Corylus pollen can be present as airborne particles of PM₁size.This study demonstrated that it is possible to use q PCR to identify and quantify pollen and fungi in the PM₁ fraction,and it has improved our understanding of the qualitative and quantitative relationship between the PM₁ and the inhalable fungal particles in indoor air in homes.(2)The cleaning workers were exposed to elevated concentrations of fungi during their work day in nursing homes,and Penicillium was the dominant genus to which the workers were exposed during the cleaning work.The two species Aspergillus candidus and P.italicum had the highest TIP,while A.niger and A.fumigatus were the most cytotoxic.The geometric mean concentration of risk fungi from the personal exposure samples from the cleaning staff was 71 CFU/m³,which is higher than seen in the indoor stationary samples(28 CFU/m³)and the outdoor references samples(12 CFU/m³).This is highlighting the higher fungal exposure risk to cleaning workers.(3)A significant effect of season,work task,and person was found on the personal exposure to bacteria and to endotoxin in wastewater treatment plant.Wastewater related workers were exposed to higher levels of bacteria(GM=352 CFU/m³)than no wastewater related workers(GM=158 CFU/m³;p=0.01).Enterobacter cloacae was found only in the autumn and was the only pathogen found both in personal exposure and working environment samples.Some accordance is found between the different methods used for risk evaluation and the results show that the wastewater treatment plants have a higher exposure risk.(4)The concentration of airborne bacteria increased significantly during the performance activities compared to the background level of 848 CFU/m³,with the highest concentration measured in connection with clarinet playing(5484 CFU/m³)and followed by trumpet playing(3491 CFU/m³),singing(2848 CFU/m³)and transverse flute playing(2403 CFU/m³).The number of deposited number of bacteria was found to be decreasing with distance from the source.Stenotrophomonas maltophilia was found in the mouthpiece of the trumpet as well as in the air sampled close to the trumpeter.The risk of infection were decreasing with distance from the source and increasing with duration of the activity.