Daily indoor-to-outdoor temperature and humidity relationships: a sample across seasons and diverse climatic regions

The health consequences of heat and cold are usually evaluated based on associations with outdoor measurements collected at a nearby weather reporting station. However, people in the developed world spend little time outdoors, especially during extreme temperature events. We examined the association between indoor and outdoor temperature and humidity in a range of climates. We measured indoor temperature, apparent temperature, relative humidity, dew point, and specific humidity (a measure of moisture content in air) for one calendar year (2012) in a convenience sample of eight diverse locations ranging from the equatorial region (10 °N) to the Arctic (64 °N). We then compared the indoor conditions to outdoor values recorded at the nearest airport weather station. We found that the shape of the indoor-to-outdoor temperature and humidity relationships varied across seasons and locations. Indoor temperatures showed little variation across season and location. There was large variation in indoor relative humidity between seasons and between locations which was independent of outdoor airport measurements. On the other hand, indoor specific humidity, and to a lesser extent dew point, tracked with outdoor, airport measurements both seasonally and between climates, across a wide range of outdoor temperatures. These results suggest that, in general, outdoor measures of actual moisture content in air better capture indoor conditions than outdoor temperature and relative humidity. Therefore, in studies where water vapor is among the parameters of interest for examining weather-related health effects, outdoor measurements of actual moisture content can be more reliably used as a proxy for indoor exposure than the more commonly examined variables of temperature and relative humidity.

[1]  S. Tong,et al.  The influence of season and ambient temperature on birth outcomes: a review of the epidemiological literature. , 2011, Environmental research.

[2]  J. Jaakkola,et al.  Significance of humidity and temperature on skin and upper airway symptoms. , 2003, Indoor air.

[3]  G. Donaldson.  Cold exposure and winter mortality from ischaemic heart disease, cerebrovascular disease, respiratory disease, and all causes in warm and cold regions of Europe , 1997, The Lancet.

[4]  R. Steadman.  The Assessment of Sultriness. Part I: A Temperature-Humidity Index Based on Human Physiology and Clothing Science , 1979 .

[5]  A Haines,et al.  Effects of ambient temperature on the incidence of myocardial infarction , 2009, Heart.

[6]  Cécile Viboud,et al.  Absolute Humidity and the Seasonal Onset of Influenza in the Continental United States , 2010, PLoS biology.

[7]  D. Gavhed,et al.  Inhalation of cold air increases the number of inflammatory cells in the lungs in healthy subjects. , 1998, The European respiratory journal.

[8]  J. Castellani,et al.  Cold exposure: human immune responses and intracellular cytokine expression. , 2002, Medicine and science in sports and exercise.

[9]  I Martinac,et al.  Indoor climate and air quality. Review of current and future topics in the field of ISB study group 10. , 1998, International journal of biometeorology.

[10]  Commentary: What measure of temperature is the best predictor of mortality? , 2012, Environmental research.

[11]  H. Koskela.  Cold air-provoked respiratory symptoms: the mechanisms and management , 2007, International journal of circumpolar health.

[12]  Phillip Biddulph,et al.  Building characteristics as determinants of propensity to high indoor summer temperatures in London dwellings , 2012 .

[13]  THE COOLING EFFICIENCY OF SWEAT EVAPORATION , 1962 .

[14]  Michelle L. Bell,et al.  Weather-Related Mortality: How Heat, Cold, and Heat Waves Affect Mortality in the United States , 2009, Epidemiology.

[15]  Shilu Tong,et al.  Ambient Temperature and Morbidity: A Review of Epidemiological Evidence , 2011, Environmental health perspectives.

[16]  R. G. Steadman,et al.  The Assessment of Sultriness. Part II: Effects of Wind, Extra Radiation and Barometric Pressure on Apparent Temperature , 1979 .

[17]  R. Basu,et al.  The effects of temperature and use of air conditioning on hospitalizations. , 2010, American journal of epidemiology.

[18]  Makoto Shoji,et al.  Absolute humidity as a deterministic factor affecting seasonal influenza epidemics in Japan. , 2011, The Tohoku journal of experimental medicine.

[19]  W. Keatinge.  Winter mortality and its causes , 2002, International journal of circumpolar health.

[20]  M. Medina-Ramón,et al.  Temperature, temperature extremes, and mortality: a study of acclimatisation and effect modification in 50 US cities , 2007, Occupational and Environmental Medicine.

[21]  Sébastien Ballesteros,et al.  The role of weather on the relation between influenza and influenza-like illness. , 2012, Journal of theoretical biology.

[22]  J. Healy,et al.  Excess winter mortality in Europe: a cross country analysis identifying key risk factors , 2003, Journal of epidemiology and community health.

[23]  W. J. Saucier,et al.  Principles of meteorological analysis , 1955 .

[24]  D. Dockery,et al.  The relationship between indoor and outdoor temperature, apparent temperature, relative humidity, and absolute humidity. , 2013, Indoor air.

[25]  K. Collins,et al.  Low indoor temperatures and morbidity in the elderly. , 1986, Age and ageing.

[26]  R. F. Goldman,et al.  Predicting sweat loss response to exercise, environment and clothing , 2004, European Journal of Applied Physiology and Occupational Physiology.

[27]  S. Tong,et al.  Ambient Temperature and Cardiorespiratory Morbidity: A Systematic Review and Meta-analysis , 2012, Epidemiology.

[28]  Rupa Basu,et al.  High ambient temperature and mortality: a review of epidemiologic studies from 2001 to 2008 , 2009, Environmental health : a global access science source.

[29]  J Shaman,et al.  Socioeconomic and Outdoor Meteorological Determinants of Indoor Temperature and Humidity in New York City Dwellings. , 2013, Weather, climate, and society.

[30]  Barbara M. Miller,et al.  Introductory Statistics: A Conceptual Approach Using R , 2012 .

[31]  Antonella Zanobetti,et al.  The effect of weather on respiratory and cardiovascular deaths in 12 U.S. cities. , 2002, Environmental health perspectives.