Selection of the pollutants

An important objective of the project is to actually measure the indoor/outdoor relation, and related concentration levels for a selection of compounds. The scope of the project also includes a number of limitations regarding the choice of pollutants. Compounds, only emitted from indoor sources will not be retained. Only pollutants from general sources (e.g. traffic , non-specific industry, heating, etc.) will be included. Furthermore, the selection of pollutants takes into account compounds that were already included in other studies conducted in Flanders.

It was decided to sample compounds from each “main type”, namely: particulate matter, combustion products, and a selection of VOC’s.

For particulate matter, the PM fractions will be monitored, being PM10, PM2.5 and PM1.

Based on the list of priority pollutants formulated in the JRCs INDEX - project, the category of combustion products is furthermore narrowed to CO and NO2. Taking into account the scope of this project, it was decided to retain NO2 and to drop CO since this pollutant has very specific indoor sources and has merely peak exposure problems regarding health. PAH ’s will not be measured in this survey because of the specific measurement methods required.

Within the category of VOC’s a selection is made, based on health effects, literature (principally governmental such as the INDEX-project, the Flemish decree on indoor policy, etc.. ) and the feasibility of their respective measurement methods. Due to their specific, and expensive, measurement methods, terpenes, pesticides and bromated flame retardants will not be measured in this first Flemish indoor exposure survey.

It was decided to measure benzene, toluene, ethylbenzene, styrene and the xylenes, which are not only easily measured, but also prioritised compounds in several legislative documents and studies. Formaldehyde also has the highest priority in the INDEX- project and is here included, as well as acetaldehyde since it is specified in the Flemish indoor legislation and in ISO 16000-3. Also, the other VOC’s specified in the Flemish decree are included in the survey, namely trichloroethene and tetrachloroethene. 1,2,4-Trimethylbenzene and p-dichlorobenzene are measured based on their selection in EXPOLIS, INDEX, ISO-16000-1. TVOC (C6-C16) will be included too. Benzene and formaldehyde are classified as Class 1 carcinogenic by the IARC. Tricloroethene and tetrachloroethene are classified in Class 2A. Styrene and Acetaldehyde are classified in class 2B.

Methyl Tertiary Butyl Ether (MTBE) is also included in this survey. It is emitted by outdoor and has no known indoor sources since it is and gasoline additive. Therefore it can be used as a tracer. Tracers are (chemical) compounds that generally can easily be measured and are used to follow processes of interest. In this survey MTBE will be used as an indicator for the infiltration/ventilation of outdoor air into the indoor environment.