Indoor and outdoor air concentrations of BTEX and NO₂: correlation of repeated measurements

Abstract

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.

Determining the Levels of Volatile Organic Pollutants in Urban Air Using a Gas Chromatography-Mass Spectrometry Method

“…At sites 1–3 and 7–9, that is, on busy streets and street crossings, short-term sampling concentrations found for benzene in air exceeded 10  μ g/m 3 , the recommended annual average limit [11]. The ratio of toluene to benzene concentration ranges between 1.6 and 6, comparable to values found in similar studies [8, 14, 15]. BTEX concentrations in urban atmosphere show a wide variability, caused by specific conditions, including the dimension and technical state of the vehicle fleet, the road traffic intensity, and meteorological factors.…”

“…Of the volatile atmospheric contaminants, benzene, toluene, ethyl-benzene, and xylenes, shortly named BTEX, mainly originate from exhaust gases of internal combustion vehicles and are of particular concern in urban areas with intense road traffic, hence the interest for monitoring their atmospheric concentrations [4, 6–8]. …”

Maternal Personal Exposure to Airborne Benzene and Intrauterine Growth

“…In our study, women carried the sampler at the same stage of fetal development and for a whole week to try to capture most of the usual situations of exposure. A German study with repeated measurements of indoor and outdoor benzene levels 6–13 months apart showed important intraindividual variation; however, after adjustment for season of measurement and region, the between-home standard deviation of benzene levels was greater than the within-home standard deviation, and the seasonal variations in benzene levels showed similar patterns across locations of measurement (Topp et al 2004). Although the absolute value of exposure is expected to vary with time, it is plausible that the distribution of the population into exposure tertiles exhibits limited variations across time; that is, women in the highest exposure tertile at 27 gestational weeks may also correspond to a large proportion of the women in the highest tertile of exposure averaged over a longer period.…”

Association of gas cooking with children’s respiratory health: results from GINIplus and LISAplus birth cohort studies

“…Gas cooking, together with gas heating, is a main source of indoor nitrogen dioxide (NO 2 ) (Koistinen et al., 2008). For this reason and because of the difficulty in obtaining indoor measurements of NO 2 (Cyrys et al., 2000; Topp et al., 2004), most epidemiological studies use gas cooking as a surrogate of indoor exposure to this pollutant.…”