Relationships of Personal Exposure to Temperature, Relative Humidity and Fine Particles with Outdoor Temperature

Abstract

ISEE-0497 Background and Objective: Exposure to extreme temperatures and airborne particles occur often simultaneously and can both affect the respiratory and cardiovascular health. Thus, they can be confounders for each other in epidemiological time series studies. Generally, outdoor temperature has been used as an estimate for individual temperature exposure. In this study, longitudinal associations between outdoor temperature and personal environmental temperature, relative humidity (RH) and particles are reported for the heating season. Methods: Personal exposure to temperature, RH and fine particles (PM2.5) were repeatedly measured (4–11 times) over a 24h time period with a 1-min resolution in 43 elderly non-smoking heart disease patients during the heating season in Kuopio, Finland. In addition, personal daily exposure to combustion particles (indicator PM2.5-Abs; absorption coefficient) as well as concentrations of outdoor PM2.5 and PM2.5-Abs, and outdoor temperature were used in the analysis. Spearman correlation coefficients (r) between outdoor and indoor variables were analyzed for each individual separately and then the median was taken. Results: Outdoor temperature varied from −22 to +4 °C during the measurements. As expected, the correlation between outdoor and personal 24h average temperature was low for most individuals (r = 0.14), but outdoor temperature described reasonably well the daily minimum 1-min temperature exposure (r = 0.50), especially for individuals who spent more than 1h outdoors (r = 0.77). High median correlation (r = 0.80) was observed between central site temperature and personal exposure to RH. There was a weak negative correlation between outdoor temperature and personal exposure to PM2.5 and PM2.5-Abs (r = –0.25 and r = –0.32, respectively). Conclusions: During heating season, associations between outdoor temperature and the daily personal exposure to temperature, PM2.5 and PM2.5-Abs were weak. The minimum temperature the subjects were exposed to while outdoors and the daily personal exposure to relative humidity on daily level were related to the daily outdoor temperature. Tekes/ERDF funding (70078/04; 2229/31/04) is acknowledged.