International Journal of Hygiene and Environmental Health
Daily time spent indoors in German homes – Baseline data for the assessment of indoor exposure of German occupants
Introduction
Problems relating to indoor air quality and complaints associated with the indoor environment often lead to measurements of physical, chemical and biological parameters in homes and offices. The knowledge about time spent indoors is absolutely necessary for an exposure assessment of the persons concerned. Whereas in the United States and in Canada extensive time-activity studies were carried out in the nineties (Leech et al., 2002), this kind of knowledge is rare or insufficiently published in Europe, especially in Germany. The often cited data of Szalai (1972) and Chapin (1974) are more than 30 years old. Time spent in the house for German residents over 9 years old has been recorded in 5400 households (12,600 persons) by the Federal Statistical Office Germany in 2001/02 using time-activity diaries. The published analyses do not enable conclusions about the locations where the activities took place (Ehling et al., 2003). The German Socio-Economic Panel surveyed nearly 12,000 households in 2002. It contains time-activity data, but does not include questions on the locations (http://diw.de). The German Environmental Survey carried out by the Federal Environmental Agency in 1990/92 registered, among other things, time spent at home for a random sample of 4500 German persons. Only an abstract has been published (Krause and Schulz, 1998). Dörre (1997) tested a diary to determine the duration of stay in different microenvironments and obtained time-activity patterns for 52 toddlers (1987) and 79 students (1993/94). His results are very exact but, being restricted to these special groups, are not representative of the whole population. This unsatisfactory situation was also criticized in a report of the “Working Group Risk Assessment in Environmental Medicine” (Schmidt-Höpfner and Sagunski, 1995).
The German population-based study “Dampness and mould in homes” examined 5530 apartments and single family houses with the aim of obtaining a representative overview of the situation in German homes regarding damp spots and visible mould growth. In addition to causes and factors affecting the development of signs of dampness, information was obtained for almost 12,000 persons living in these 5530 homes (Brasche et al., 2003). The questionnaire for the occupants included a question on the mean length of stay per day for every person. Table 2, Table 3, Table 4 present the mean duration of stay in homes classified by personal characteristics, characteristics of the home, building, building location and the habits of the occupants. This enables users of the time tables to make an assessment, as exact as possible, of exposure time in the field of indoor measurements in the home.
Section snippets
Method
A random sample of 5530 homes was investigated between September 2000 and April 2001 using a modular tool which combines standardized questions and a protocol for expert evaluation of building and equipment factors. The module “Person” recorded answers for each person concerning sex, age, health status and mean daily duration of stay at home for all occupants of the apartment. Persons registered as occupants but not living at home for most of the week (e.g. students, studying in another city)
Results
Fig. 1 compares the persons of the cross-sectional study “Dampness and moulds in homes” to the whole population of Germany regarding age structure. It shows that older age groups are slightly over-represented and the youngest age group is smaller in the described study. But in general the correspondence is relatively good.
The mean time spent at home, related to the whole sample of 11,918 persons, is 15.7 h. A description of this variable is given in Table 1. Women spend more time at home (16.6 h)
Discussion
The big advantage of this analysis of time spent at home is the high number of persons included, derived from a population-based random sample. The validity of the time-value responses from one person in the household is probably not as reliable as time data obtained from time-activity diaries.
Time activity patterns or comparable data are rare for the German population. Dörre (1997) described the mean time of stay per day at different places (home included) for 52 toddlers, which were surveyed
Conclusion
The mean time spent indoors at home found by the study “Dampness and mould in homes” is 15.7 h/day. This mean differs considerably with regard to gender, age, characteristics and location of the home. An association between time spent at home and the habits of the occupants is apparent. The described results seem to be valid and consistent in the context of available national and international publications.
Acknowledgment
The German population based study “Dampness and mould in homes” was funded by Bundesverband des Schornsteinfegerhandwerks – Zentralinnungsverband (ZIV).
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