title: Exploration of the effects of classroom humidity levels on teachers' respiratory symptoms.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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)].
  
  
  CONCLUSIONS
  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.
authors.affiliation: Epidemiology Department, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, Chapel Hill, NC, USA. kangelongaetz@gmail.com.
authors.forename: Kim A
authors.identifier: http://orcid.org/0000-0002-8530-0066
authors.initials: KA
authors.lastname: Angelon-Gaetz
authors.affiliation: Epidemiology Department, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, Chapel Hill, NC, USA.
authors.forename: David B
authors.initials: DB
authors.lastname: Richardson
authors.affiliation: Epidemiology Department, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Stephen W
authors.initials: SW
authors.lastname: Marshall
authors.affiliation: Center for Environmental Medicine, Asthma, and Lung Biology, University of North Carolina, Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Hernandez
mesh_terms: D000328:Adult; D059366:Asthma, Occupational / Q000209:etiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006813:Humidity / Q000009:adverse effects*; D008297:Male; D009657:North Carolina; D016273:Occupational Exposure / Q000009:adverse effects* / Q000032:analysis; D010865:Pilot Projects; D016012:Poisson Distribution; D012044:Regression Analysis; D012306:Risk; D012574:Schools
keywords: Allergies; Asthma; Classroom humidity; Longitudinal study; Teachers; Workplace
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