|3 Measurement and Evaluation for the Determination of Indoor Air Chemicals|
Research Institute for Environment, Agriculture and Fisheries,Osaka Prefecture Government
Hazardous chemical substances including formaldehyde are widely used in building materials and adhesive agents. They are one of the causative substances that cause sick building syndrome from the viewpoint of indoor air pollution. The Ministry of Health, Labour and Welfare enacted a “Guideline for indoor air pollution” (December, 2002) in order to regulate indoor hazardous organic contaminant, since awareness of chemical health effects on humans is on the rise. This paper describes the measurement and evaluation for the determination of indoor air chemicals with respect to the guidelines that have been examined.
To evaluate whether the concentration of indoor air pollutants meets the indicator value, selection of collection and measurement methods suitable for the purpose is done by strictly regulating indoor conditions and collection. In the case of a new residential house, in order to measure the maximum concentration of pollutants in a room's air, first the room to be measured is ventilated for 30 minutes. Afterwards, a 30-minute collection is conducted following a more than 5-hour seal-up. In the case of an inhabited house, a 24-hour sequential collection is conducted for the purpose of comprehending chemical concentrations and the amount of exposure under the normal conditions. Basically, each collection is conducted twice at a set place. Samples are collected at the following three points: the living room, a bed room in the house, one place outside the house. Within the house, samples are collected at a point 1 m away from the wall, near the center of the room; while outside the house samples are taken at a point 2 - 5m away from an external wall and at a ventilation opening. With respect to height for collection, samples are collected at a point 0.3 - 1.5 m up from the floor or ground in relation to the source of chemical diffusion.
Chemical substances whose indoor concentration guideline values are set based on toxicity indicators are classified into the following four groups: acetaldehydes, volatile organic compound, phthalate compounds and agrichemicals, which contain 13 substances in total. The outline for measurement of indoor air chemicals is described in Table 1.
The container sampling method is used to measure volatile organic compounds. A stainless steel container (3L–15L capacity) whose inner surface is deactivation-treated (e.g. electrochemical polishing, oxidized coating and silica coating) is used as a sample collection container. The container which is washed after heat treatment under reduced pressure and depressurized in advance (under 13Pa, approx. 0.1mmHg) is used for collecting samples at constant flow using a Mass Flow Controller. There are two methods: one is the decompression method which finishes sampling under atmospheric pressure; the other is the pressurization method which collects at approximately 200kPa (approx. 1500mmHg) using a pressurization pump. The container with collected samples is connected to a special sample concentration device and roughly 100mL of the collected sample is concentrated and analyzed. This method can simultaneously measure many compounds, including volatile organic compounds. The samples collected can be repeatedly analyzed. This method can also be applied to a wide range of sample concentrations.
Solid phase adsorption/Solvent extraction is the method used to analyze eluted components by dissolving out the substances for measurement with a solvent. Afterwards, samples are collected at constant flow using a Mass Flow Controller in a glass tube filled with a collection agent. It is used for measurement of a wide range of substances, such as volatile organic compounds, phthalate compounds and agrichemicals. Since the concentrated substances for measurement are diluted using a solvent, increasing the amount of sample collected is required. Consequently, adsorbents with strong collection ability must be selected. Also, since the blank value of the extracted solvent directly influences the quantitative lower limit, the use of highly purified solvents is required.
Solid phase adsorption/Thermal desorption is the method used to analyze substances for measurement collected by thermal desorption. Afterwards, samples are collected at constant flow using a Mass Flow Controller in a glass tube filled with a collection agent. It is used for measurement of volatile organic compound and phthalate compounds. Samples collected are induced into a GC/MS device and a heat sample induction device is required for analysis. This method is suitable for the analysis of low concentration samples because the total amount of samples collected can be used for analysis. It is impossible to re-analyze using this method. When the concentration of substances for analysis can not be predicted, several samples must be collected by changing the collection amount using several collection tubes.