Abstract
ABSTRACT Bioaerosols are an important cause of indoor pollution, and the microorganisms adhering to PM2.5 adversely affect on human health. People spend approximately 90% of their day indoors. Most research has focused on the concentration and influencing factors, with less attention paid to the correlation between microbial activity and air quality. In this study, we used a modified fluorescein diacetate hydrolysis method to measure the indoor and outdoor microbial activity in PM2.5 during three seasons in Beijing. The microbial activity indoors and outdoors ranged from 0.155 to 5.388 ng m-3 and 0.091 to 5.740 ng m-3 sodium fluorescein, respectively, which were not significantly different; however, the indoor air was affected by the outdoor environment to some extent. During the observation period, the microbial activity under excellent air quality, good air quality and slight pollution decreased as follows: autumn > winter > summer. In summer and autumn, the microbial activity was highest under excellent air quality conditions, and in summer, the activity under both excellent and good air quality conditions was obviously higher than that under slight pollution. We observed different variations in microbial activity in rooms that were closed or ventilated, and inferred that the indoor microbial activity was closely associated with the ventilation status. Overall, 20 minutes of ventilation can achieve better air exchange when the air quality is excellent. However, the ventilation duration should be appropriately reduced under polluted conditions. This study provides a new insight for indoor air quality evaluations from the perspective of microbial activity.
Highlights
Indoor air quality is closely related to human health and work efficiency
This work aims to address the following three questions: (1) How do indoor and outdoor air quality levels change in different seasons and under different pollution levels with microbial activity as an indicator? (2) Does the outdoor environment have an impact on indoor microbial activity? (3) How can a scientific ventilation method be adopted in winter to reduce the impact of indoor microorganisms on health?
Our results provide a theoretical basis for future evaluations of indoor air quality
Summary
Indoor air quality is closely related to human health and work efficiency. The health risks associated with exposure to poor quality indoor air may far exceed those associated with outdoor pollution, and are more likely to cause harm to vulnerable groups (Mendes et al, 2013). Microbial aerosols are an important fraction of bioaerosols, and high levels of microbial aerosols directly decrease indoor air quality; some harmful microorganisms can directly or indirectly threaten human health depending on the environmental conditions. People who live and work indoors long-term might show many symptoms, such as headache, nausea, dizziness and inattention, and this has been termed sick building syndrome (SBS)
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