Skip to main content

Exploration of the effects of classroom humidity levels on teachers’ respiratory symptoms



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.

This is a preview of subscription content, access via your institution.


  • Angelon-Gaetz KA, Richardson DB, Lipton DM, Marshall SW, Lamb B, LoFrese T (2015) The effects of building-related factors on classroom relative humidity among North Carolina schools participating in the ‘Free to Breathe, Free to Teach’study. Indoor Air 25:620–630

    Article  CAS  Google Scholar 

  • Arlian LG, Morgan MS, Neal JS (2002) Dust mite allergens: ecology and distribution. Curr Allergy Asthma Rep 2:401–411

    Article  Google Scholar 

  • Bakke JV, Norback D, Wieslander G, Hollund BE, Florvaag E, Haugen EN, Moen BE (2008) Symptoms, complaints, ocular and nasal physiological signs in university staff in relation to indoor environment—temperature and gender interactions. Indoor Air 18:131–143. doi:10.1111/j.1600-0668.2007.00515.x

    Article  CAS  Google Scholar 

  • Behavioral Risk Factor Surveillance System (BRFSS) Calendar Year 2010 Results (2011) North Carolina State Center for Health Statistics, Raleigh. Available from

  • Beunckens C, Sotto C, Molenberghs G (2008) A simulation study comparing weighted estimating equations with multiple imputation based estimating equations for longitudinal binary data. Comput Stat Data Anal 52:1533–1548. doi:10.1016/j.csda.2007.04.020

    Article  Google Scholar 

  • Bind MA et al (2014) Effects of temperature and relative humidity on DNA methylation. Epidemiology (Cambridge, MA) 25:561–569. doi:10.1097/EDE.0000000000000120

    Article  Google Scholar 

  • Buckley JP, Richardson DB (2012) Seasonal modification of the association between temperature and adult emergency department visits for asthma: a case-crossover study. Environmental Health 11:55-069X-011-055. doi:10.1186/1476-069X-11-55

    Article  Google Scholar 

  • Casanova LM, Jeon S, Rutala WA, Weber DJ, Sobsey MD (2010) Effects of air temperature and relative humidity on coronavirus survival on surfaces. Appl Environ Microbiol 76:2712–2717. doi:10.1128/AEM.02291-09

    Article  CAS  Google Scholar 

  • Centers for Disease Control and Prevention (2009) 2008 Behavioral Risk Factor and Surveillance System (BRFSS) asthma call-back questionnaire for adults. Centers for Disease Control and Prevention, Atlanta

    Google Scholar 

  • Chao HJ, Schwartz J, Milton DK, Burge HA (2002) Populations and determinants of airborne fungi in large office buildings. Environ Health Perspect 110:777–782

    Article  Google Scholar 

  • Dangman KH, Bracker AL, Storey E (2005) Work-related asthma in teachers in Connecticut: association with chronic water damage and fungal growth in schools. Conn Med 69:9–17

    Google Scholar 

  • Donders ART, van der Heijden GJ, Stijnen T, Moons KG (2006) Review: A gentle introduction to imputation of missing values. J Clin Epidemiol 59(10):1087–1091

    Article  Google Scholar 

  • Ebbehoj NE et al (2005) Molds in floor dust, building-related symptoms, and lung function among male and female school teachers. Indoor Air 15(Suppl 10):7–16. doi:10.1111/j.1600-0668.2005.00352.x

    Article  Google Scholar 

  • Eng A, Mannetje AT, Douwes J, Cheng S, McLean D, Ellison-Loschmann L, Pearce N (2010) The New Zealand workforce survey II: occupational risk factors for asthma. Ann Occup Hyg 54:154–164. doi:10.1093/annhyg/mep098

    Article  Google Scholar 

  • Fisk WJ, Eliseeva EA, Mendell MJ (2010) Association of residential dampness and mold with respiratory tract infections and bronchitis: a meta-analysis. Environ Health Glob Access Sci Source 9:72. doi:10.1186/1476-069X-9-72

    Google Scholar 

  • Fletcher AM, London MA, Gelberg KH, Grey AJ (2006) Characteristics of patients with work-related asthma seen in the New York State Occupational Health Clinics. J Occup Environ Med 48:1203–1211. doi:10.1097/01.jom.0000245920.87676.7b

    Article  Google Scholar 

  • Gaetz K (2014) Free to breathe, free to teach: indoor air quality in schools and respiratory health of teachers. Dissertation, University of North Carolina at Chapel Hill. ProQuest, UMI Dissertations Publishing. doi:10.13140/2.1.1739.0403

  • Global Initiative for Asthma (GINA) (2014) Global strategy for asthma management and prevention. Available from

  • Jaakkola JJK (2006) Temperature and Humidity. In: Frumkin H, Geller R, Rubin IL, Nodvin J (eds) Safe and healthy school environments. Oxford University Press, Oxford, pp 46–57

    Chapter  Google Scholar 

  • Karim YG, Ijaz MK, Sattar SA, Johnson-Lussenburg CM (1985) Effect of relative humidity on the airborne survival of rhinovirus-14. Can J Microbiol 31:1058–1061

    Article  CAS  Google Scholar 

  • Kielb C, Lin S, Muscatiello N, Hord W, Rogers-Harrington J, Healy J (2014) Building-related health symptoms and classroom indoor air quality: a survey of school teachers in New York State. Indoor Air. doi:10.1111/ina.12154

    Google Scholar 

  • Lowen AC, Mubareka S, Steel J, Palese P (2007) Influenza virus transmission is dependent on relative humidity and temperature. PLoS Pathog 3:1470–1476. doi:10.1371/journal.ppat.0030151

    Article  CAS  Google Scholar 

  • Matthews TG, Fung KW, Tromberg BJ, Hawthorne AR (1986) Impact of indoor environmental parameters on formaldehyde concentrations in unoccupied research houses. J Air Pollut Control Assoc 36:1244–1249

    Article  CAS  Google Scholar 

  • Mazurek JM et al (2008) Work-related asthma in the educational services industry: California, Massachusetts, Michigan, and New Jersey, 1993–2000. Am J Ind Med 51:47–59. doi:10.1002/ajim.20539

    Article  Google Scholar 

  • Mirabelli MC, Wing S, Marshall SW, Wilcosky TC (2006) Asthma symptoms among adolescents who attend public schools that are located near confined swine feeding operations. Pediatrics 118:e66–e75. doi:10.1542/peds.2005-2812

    Article  Google Scholar 

  • Park JH, Schleiff PL, Attfield MD, Cox-Ganser JM, Kreiss K (2004) Building-related respiratory symptoms can be predicted with semi-quantitative indices of exposure to dampness and mold. Indoor Air 14:425–433. doi:10.1111/j.1600-0668.2004.00291.x

    Article  Google Scholar 

  • Patovirta RL, Husman T, Haverinen U, Vahteristo M, Uitti JA, Tukiainen H, Nevalainen A (2004) The remediation of mold damaged school—a three-year follow-up study on teachers’ health. Cent Eur J Public Health 12:36–42

    CAS  Google Scholar 

  • Rudblad S, Andersson K, Stridh G, Bodin L, Juto JE (2001) Nasal hyperreactivity among teachers in a school with a long history of moisture problems. Am J Rhinol 15:135–141

    Article  CAS  Google Scholar 

  • Sahakian NM, White SK, Park JH, Cox-Ganser JM, Kreiss K (2008) Identification of mold and dampness-associated respiratory morbidity in 2 schools: comparison of questionnaire survey responses to national data. J Sch Health 78:32–37. doi:10.1111/j.1746-1561.2007.00263.x

    Article  Google Scholar 

  • Sato M, Fukayo S, Yano E (2003) Adverse environmental health effects of ultra-low relative humidity indoor air. J Occup Health 45:133–136

    Article  Google Scholar 

  • Sattar SA, Karim YG, Springthorpe VS, Johnson-Lussenburg CM (1987) Survival of human rhinovirus type 14 dried onto nonporous inanimate surfaces: effect of relative humidity and suspending medium. Can J Microbiol 33:802–806

    Article  CAS  Google Scholar 

  • Shaman J, Kohn M (2009) Absolute humidity modulates influenza survival, transmission, and seasonality. Proc Natl Acad Sci USA 106:3243–3248. doi:10.1073/pnas.0806852106

    Article  CAS  Google Scholar 

  • Thomas G, Burton NC, Mueller C, Page E, Vesper S (2012) Comparison of work-related symptoms and visual contrast sensitivity between employees at a severely water-damaged school and a school without significant water damage. Am J Ind Med 55:844–854. doi:10.1002/ajim.22059

    Article  Google Scholar 

  • Thorn A, Lewne M, Belin L (1996) Allergic alveolitis in a school environment. Scand J Work Environ Health 22:311–314

    Article  CAS  Google Scholar 

  • U.S. EPA (2009) Indoor air quality tools for schools reference guide. In: IAQ tools for schools action kit, EPA 402/K-07/008. United States Environmental Protection Agency (U.S. EPA), Washington

  • Whelan EA, Lawson CC, Grajewski B, Petersen MR, Pinkerton LE, Ward EM, Schnorr TM (2003) Prevalence of respiratory symptoms among female flight attendants and teachers. Occup Environ Med 60:929–934

    Article  CAS  Google Scholar 

  • Wolkoff P, Kjaergaard SK (2007) The dichotomy of relative humidity on indoor air quality. Environ Int 33:850–857. doi:10.1016/j.envint.2007.04.004

    Article  CAS  Google Scholar 

  • World Health Organization (2009) WHO guidelines for indoor air quality—dampness and mould. WHO Regional Office for Europe, Copenhagen

    Google Scholar 

  • Zou G, Donner A (2013) Extension of the modified Poisson regression model to prospective studies with correlated binary data. Stat Methods Med Res 22:661–670. doi:10.1177/0962280211427759

    Article  CAS  Google Scholar 

Download references


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.

Author information

Authors and Affiliations


Corresponding author

Correspondence to Kim A. Angelon-Gaetz.

Ethics declarations

Conflict of interest

The authors declare they have no competing interests.

Ethical approval

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

Informed consent was obtained from all individual participants included in this study.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Supplementary material 1 (DOCX 30 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

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).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:


  • Teachers
  • Asthma
  • Allergies
  • Longitudinal study
  • Workplace
  • Classroom humidity