Comparing bioaerosol emission after flushing in squat and bidet toilets: Quantitative microbial risk assessment for defecation and hand washing postures

Indoor bathroom is an essential place in daily human life, and the toilet in it releases bioaerosols with varying emission characteristics, having a noticeable influence on human health. Especially after flushing, the next user of the shared toilet faces a significant health risk. Therefore, this research sampled and compared Staphylococcus aureus bioaerosol emission characteristics in squat and bidet toilets with different exposure heights for defecation and hand washing postures under two different ventilation scenarios. Then, a quantitative health risk model concerning the annual probability of infection and disease burden (DB) was performed for different exposed populations during their use of the shared toilet after flushing with time. The highest bioaerosol concentration was in bathroom with the squat toilet. The infection risk of adult male was 7.59%-26.72% higher than that of the other exposure populations. For defecation posture, 8.43%-59.11% higher health infection risks were observed for squat toilet than for bidet toilet. The infection risks in hand washing posture were 2.12-3.10 times lower than those in defecation posture. The assessment results of DB approximately matched those of infection risk for all exposure scenarios. For defecation posture under turned-off, air-exhaust ventilation scenario, the DB was 1.28-1.95 times higher than that under turned-on, air-exhaust ventilation scenario in both toilets. After flushing at 0-35 min, DB in hand washing posture were acceptable for all exposed populations. The present study provides for the first time innovative information of guidelines for controlling health risks of two types of shared toilet.

Automated summary

This research compared the characteristics of Staphylococcus aureus bioaerosol emissions from squat and bidet toilets under different exposure heights for defecation and hand washing postures. The study found that the highest bioaerosol concentration was in squat toilets, and adult males faced a higher infection risk compared to other populations. Additionally, the infection risks were lower in hand washing postures compared to defecation postures.