Respiratory infections among junior high school students in upper northern Thailand: The role of building dampness and mould, biomass burning and outdoor relative air humidity (RH)

Background: Few studies exist on environmental risk factors for respiratory infections in Thai school children. Aim: To study associations between home and outdoor environment and respiratory infections among school children in Northern Thailand in dry and wet season. Methods: A repeated questionnaire survey among the children (N = 1159). Data on ambient temperature and relative air humidity (RH) and PM10 and ozone was collected from nearby monitoring stations. We used logistic regression to calculate odds ratios (OR). Results: 14.1% had current respiratory infections (last 7 days), 32.1% had any respiratory infection last 3 months, and 26.1% had any respiratory infection last 12 months with antibiotic treatment. Students with diagnosed allergy (7.7%) and diagnosed asthma (4.7%) had more often respiratory infections (ORs 1.40-5.40; p < 0.05). Current respiratory infections were more common in dry (18.1%) than in wet season (10.4%) (p < 0.001) and was associated with indoor mould (OR 2.16; p = 0.024) and outdoor RH (OR 1.34 per 10% RH; p = 0.004.) in the total material. In wet season, mould (OR 2.32; p = 0.016), window pane condensation (OR 1.79; p = 0.050), water leakage (OR 1.82; p = 0.018), environmental tobacco smoke (ETS) (OR 2.34; p = 0.003) and outdoor RH (OR 2.70 per 10% RH; p = 0.01) were risk factors for current respiratory infections. In dry season, mould (OR 2.64; p = 0.004) and outdoor RH (OR 1.34 per 10% RH; p = 0.046) were associated with current respiratory infections. Irrespectively of season, biomass burning inside or outside the home was a risk factor for respiratory infections (ORs 1.32-2.34; p < 0.05). Living in a wooden house decreased the risk of respiratory infections (OR 0.56: p = 0.006). Conclusions: Dry season, high outdoor RH, household dampness, indoor mould and ETS can increase childhood respiratory infections. Living in a traditional wooden house can reduce respiratory infections, possibly due to better natural ventilation. Smoke from biomass burning can increase childhood respiratory infections in northern Thailand.

Automated summary

Respiratory infections among school children in Northern Thailand are associated with home and outdoor environment, as well as the dry and wet seasons. Risk factors for respiratory infections include dry season, high outdoor relative humidity, household dampness, indoor mould, and smoke from biomass burning. However, living in a traditional wooden house can reduce the risk.