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For studies like ours with low allergen and endotoxin concentrations, the repeatability of these concentrations over a time period as long as 6 years is low and a single measurement does not accurately reflect the true long-term exposure in the homes.

Studies on health effects of air pollutants ideally define exposure through the collection of air samples in the participants' homes. Concentrations derived from these samples are then considered as an estimate for the average concentration of air pollutants in the homes. Conclusions drawn from such studies therefore depend very much on the validity of the measured air pollution concentrations. In this paper we analysed repeated BTEX and NO(2) measurements with a time period of several months lying between the two conducted home visits. We investigated the variability of their concentrations over time by determining correlation coefficients and calculating within- and between-home variances. Our population consisted of 631 homes of participants from two cohort studies within the framework of the German study on Indoor Factors and Genetics in Asthma. Air pollutants were measured using passive samplers both indoors and outdoors. The measured BTEX concentrations were poorly correlated, with Pearson's correlation coefficient r ranging from -0.19 to 0.27. Additionally, a considerable seasonal effect could be observed. A higher correlation was found for the NO(2) concentrations with r ranging between 0.24 and 0.55. For the BTEX, the between-home variance was bigger than the within-home variance, for NO(2) both variances were of about the same order. Our results indicate that in a setting of moderate climate like in Germany, the variability of BTEX and NO(2) concentrations over time is high and a single measurement is a poor surrogate for the long-term concentrations of these air pollutants.

Recently, a study of 330 adults reported increased systolic blood pressure and higher hypertension rates in men with rhinitis. We replicated this study using data from a population-based sample of 896 subjects participating in the European Respiratory Health Survey and in a study on "Monitoring of Trends and Determinants of Cardiovascular Diseases" in Erfurt, Germany. Rhinitis was assessed by questionnaire, blood pressure was measured using a standardized method, and subjects were asked about current use of any high blood pressure medication. After adjustment for age, body mass index, and smoking, neither average systolic (p = 0.17) nor diastolic blood pressure (p = 0.60) was statistically significantly different between men with and without rhinitis. The adjusted prevalence rate of hypertension was also not different between males with and without rhinitis (p = 0.25). In addition, no statistically significant associations between rhinitis and blood pressure were seen in women. We could not confirm the conclusion of the previous study that men with rhinitis need special attention for blood pressure control.