Previous studies indicate that teachers have higher asthma prevalence than other non-industrial worker groups. Schools frequently have trouble maintaining indoor relative humidity (RH) within the optimum range (30–50 %) for reducing allergens and irritants. However, the potential relationship between classroom humidity and teachers’ health has not been explored. Thus, we examined the relationship between classroom humidity levels and respiratory symptoms among North Carolina teachers.
Teachers (n = 122) recorded daily symptoms, while data-logging hygrometers recorded classroom RH levels in ten North Carolina schools. We examined effects of indoor humidity on occurrence of symptoms using modified Poisson regression models for correlated binary data.
The risk of asthma-like symptoms among teachers with classroom RH >50 % for 5 days was 1.27 (95 % Confidence Interval (CI) 0.81, 2.00) times the risk among the referent (teachers with classroom RH 30–50 %). The risk of cold/allergy symptoms among teachers with classroom RH >50 % for 5 days was 1.06 (95 % CI 0.82, 1.37) times the risk among the referent. Low RH (<30 %) for 5 days was associated with increased risk of asthma-like [risk ratio (RR) = 1.26 (95 % CI 0.73, 2.17)] and cold/allergy symptoms [RR = 1.11 (95 % CI 0.90, 1.37)].
Our findings suggest that prolonged exposure to high or low classroom RH was associated with modest (but not statistically significant) increases in the risk of respiratory symptoms among teachers.
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Karin Yeatts supervised the project design and implementation. Bryce Koukopoulos collected data. Steve Wing assisted with research question development. The staff at the H. W. Odum Institute for Research in Social Science assisted with SAS programming and survey development. Julia Rager provided comments on the manuscript. We thank our research participants and school employees who made this study possible.
This research was supported by grants from the National Institute of Environmental Health Sciences (NIEHS) (P30ES010126)/UNC Center for Environmental Health & Susceptibility (CEHS) and the NC Translational and Clinical Sciences Institute (TraCs) 10 K Pilot Project Award Number UL1RR025747. K.A. conducted this research in fulfillment of a doctoral degree, supported by a National Institute of Occupational Safety and Health (NIOSH) Training Grant and Environmental Protection Agency (EPA) Science to Achieve Results (STAR) Fellowship. M.H. is supported by NIEHS Grant K23-ES021745.
Conflict of interest
The authors declare they have no competing interests.
The University of North Carolina’s Institutional Review Board approved all research procedures and materials (IRB# 10-1150). All procedures performed this study involving human participants were in accordance with the ethical standards of the Institutional Review Board and with the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards. This article does not contain any studies with animals performed by any of the authors.
Informed consent was obtained from all individual participants included in this study.
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Angelon-Gaetz, K.A., Richardson, D.B., Marshall, S.W. et al. Exploration of the effects of classroom humidity levels on teachers’ respiratory symptoms. Int Arch Occup Environ Health 89, 729–737 (2016). https://doi.org/10.1007/s00420-016-1111-0
- Longitudinal study
- Classroom humidity