The article reviews the health effects and exposure assessment of bioaerosols, which are aerosols or particulate matter of microbial, plant, or animal origin. Bioaerosols can cause a wide range of health issues, including infectious diseases, respiratory symptoms, allergies, and cancer. Respiratory symptoms and lung function impairment are the most extensively studied and significant health effects associated with bioaerosol exposure. The article discusses the challenges in assessing bioaerosol exposure, including the lack of valid quantitative methods and the complexity of exposure mixtures. It highlights the need for better exposure assessment tools and validation of new methods. The article also explores the potential protective effects of microbial exposure on atopy and atopic diseases, inter-individual susceptibility to biological exposures, and interactions between bioaerosols and other non-biological agents. Additionally, it addresses the identification of other biological agents that may cause adverse or protective health effects and the need for further research into various health effects and exposure routes.The article reviews the health effects and exposure assessment of bioaerosols, which are aerosols or particulate matter of microbial, plant, or animal origin. Bioaerosols can cause a wide range of health issues, including infectious diseases, respiratory symptoms, allergies, and cancer. Respiratory symptoms and lung function impairment are the most extensively studied and significant health effects associated with bioaerosol exposure. The article discusses the challenges in assessing bioaerosol exposure, including the lack of valid quantitative methods and the complexity of exposure mixtures. It highlights the need for better exposure assessment tools and validation of new methods. The article also explores the potential protective effects of microbial exposure on atopy and atopic diseases, inter-individual susceptibility to biological exposures, and interactions between bioaerosols and other non-biological agents. Additionally, it addresses the identification of other biological agents that may cause adverse or protective health effects and the need for further research into various health effects and exposure routes.