Emission af flygtige organiske forbindelser fra træ, træbaserede materialer, møbler og inventar English SummaryThe impact of emissions from wood-based furniture, interior furnishings and mateials products on the indoor environment is gaining interest. In an increasing number of cases the emissions to the indoor air have been the major product selection criterion for both consumers and professional users. Generally, wood is considered an advantageous material in a wide environmental perspective. However, the studies performed, rarely include material emissions apart from formaldehyde. This project was made to extend the limited knowledge of emissions from wood and wood-based materials, to propose a model for evaluation of emissions from these materials and methods to reduce material emissions. It has not been the intention to compare emissions from wood to other material emissions. Test Programme This study was based on analysis of chemical emission from 23 materials representing solid wood and wood-based materials commonly used in furniture and building products in 1996. The test programme was designed to include materials and products of varying complexity ranking from solid wood to surface coated veneered panels. The study included the solid wood species ash, beech, oak, spruce and pine; six different wood-based panels: particle boards of pine and spruce with different glue systems, MDF (Medium Density Fibreboard) and OSB (Oriented Strand Board) of conifer and birch plywood; different beech-veneered particle boards with use of two different glues for veneering; two flooring oils on solid beech based on urethane alkyd/linseed-oil and natural resin/linseed-oil respectively; and five different lacquered beech-veneered particle boards including nitrocellulose, UV-curing, acid-curing acrylic, water borne acrylic and polyurethane lacquers respectively. The selected 23 wood and wood-based materials and the measured emissions shall be considered as examples and can neither be considered representative for all wood-based materials used indoors nor overall representative for emissions from wood and wood-based materials. The project task, which only comprised emission from wood and woodbased products to the indoor environment does not form the basis of weighting the emission in relation to other kinds of materials or weighting the emission in relation to other indoor environment factors. Emission Testing Prior to testing and analysis the chemical substances, which were suspected to emit from the selected materials, were identified. So were the substances included in the national or international lists as health hazardous what re- gards allergy, reproduction, the peripheral or the central nervous system. The selected materials were investigated by an initial qualitative screening to identify the above mentioned substances and to determine a programme for quantitative analyses for each wood-based material. Of the approx. 150 different chemical substances identified in the screening analyses, 42 were saturated or unsaturated aldehydes or ketones, and 20 hydrocarbon of the terpene types: mono- and sesquiterpenes. The quantitative determinations were carried out by emission chamber testing at conditions common in building interiors according to a standard test method for the determination of volatile organic compounds especially referring to wood-based products. The programme for quantitative emission analyses included determination of all individual VOC's (Volatile Organic Compounds) by gas chromatography with mass spectrometric detection, liquid chromatography and photo metry by the acetylacetone method. Results Altogether 84 chemical substances were quantified by the climate chamber measurements. The predominant emissions determined from uncoated wood and wood-based materials were aldehydes, mainly acetaldehyde, propanal, butanal, pentanal and hexanal, as well as the ketone: acetone. The aldehydes varied in content in the emissons from the different materials. Formaldehyde was the predominant single emittant in the case of urea-formaldehyde glued panels. In the emission from pine also emissions of terpenes, mainly a-pinene, 3-carene and limonene were detected in large concentrations. The emissions from the tested wood-based panels vary as expected considerably dependent on the applied glue. The emissions from surface treated wood-based materials originate mainly from the oils and lacquers, and were mainly alcohols, unsaturated alde hydes, esters, glycol ethers and -esters. The emission of most aldehydes from the surface treated materials can be traced back to both coating, oil and wood. A part study of four variations of pine of different origin (northern Finland and southern Sweden respectively) and varying content of heartwood and sapwood respectively showed considerable difference in emission rates of especially 3-carene and a-pinene. It should be noted that the growth condi- tions and place can be of major importance. In the results it is not documen ted that indoor environment problems are caused by wood. Evaluation of Emission - Concentrations of chemical compounds, which were quantified, were con- verted into concentrations to which people are exposed to indoors by use of standard room considerations. Very limited indoor air concentrations were seen from solid ash, beech and oak calculated at a material-load of 0.4 m²/m³ corresponding to, for exam- ple, a floor or a table and six chairs. Solid pine gave considerably larger emissions than the other tested wood species. Solid ash, solid beech, solid oak, wood-based panels and beech-veneered particle boards are examples of materials seldom used in practice without surface treatment. A small cottage covered with a-pinene and 3-carene rich untreated pine on floor, ceiling and all four walls is an example of a scenario resulting in rela- tively high indoor air concentrations due to emissions from wood. Worst case occur if the cottage is newly built of fresh wood and if it for some rea- son is made relatively air tight, hence resulting in a low air exchange rate Evaluations of the Comfort and Health Effects The evaluation of comfort and possible health effects of emissions from wood and wood-based materials was based on experiences from the above mentioned experimental work and general principles for toxicological evaluation and literature data. The evaluation of single substances included all 84 substances quantified by the climate chamber measurements. Concentrations converted from climate chamber tests to concentrations, to which humans are exposed to in the indoor air, were compared with the toxicological determined "Lowest Concentration of Interest (LCI)" and odour threshold values. The influence of materials and products on the indoor environment was eva luated by:
LCI and S-Value LCI is defined as the lowest concentration of a certain substance, which will not - with our present knowledge - cause risk of health hazardous effects on humans. For most of the chemical substances the LCI-values in this investigation were based on irritation. More severe effects occur for most chemical substances at concentrations magnitudes higher than odour and irritation. Determination of LCI-values was difficult due to lack of toxicological data for the most of the emitted substances in the relatively low concentrations, in which the substances are present in the indoor air. In several cases the LCI-values were determined by analogue considerations. In cases, in which the data on the substances lacked, and in which it was evaluated that the most essential effect was irritation, the LCI-values were based on "RD50- values", which are determined on the basis of decrease of the respiratory frequency by mice. Irritation is thus the most frequent toxicological effect for the examined wood and the wood-based materials and gave the basis of the S-value calculations. Indoor-Relevant Time-Value The indoor-relevant time-value in days is an expression for the period of time necessary for the decline of the emissions into acceptable concentration levels, where neither irritation of eyes, nose and the upper respiratory tract nor odour may be expected. For application in practice the time is to be calculated from a product is installed in the indoor environment. Model for Evaluation The proposed model for assessment based on the S-value and the indoor-relevant time-value differentiates the emissions from the tested materials and can be used as a common basis for relative evaluations of wood, wood- based materials and products. It should, however, be noted that the absolute S-values as well as LCI-values, odour and irritation threshold values can always be questioned, and the values might change as new knowledge occur. In the case of woodbased materials, which do not cause emissions containing carcinogens, allergens or reproductive toxicants, the procedures and results of the evaluations were basically the same both according to the S-value and to the indoor-relevant time-value based on the addition of the irritative impact. The time-values based on odour thresholds, however, resulted in longer time-values than time-values based on irritation thresholds - for all decisive individual substances apart from formaldehyde - and consequently odour became determining for the indoor-relevant time-values in most cases. If health hazardous effects except from respiratory irritation due to the emis- sion could be excluded, the evaluation could solely be based on the concept for indoor-relevant time-value. Evaluation of Emission - When the indoor air is of high priority, it should be advised to select products made of lower-emitting materials, in order to limit the emission to the indoor environment. Thus a larger probability of reducing the discomfort and possible health effects caused by emission from these materials and products is achieved. Selection of relatively lower-emitting materials and products can be made by selection of materials and products with a relatively low S-value and a relatively low indoor-relevant time-value. A proposed classification based on 28 days measurement in test chamber divides wood and wood-based materials in three classes: low-emitting, medium-emitting and high-emitting materials. Among the tested surface treatments the UV-curing lacquer on beech-veneered panels was low-emitting, the acid-curing lacquer on beech-veneered panels was high-emitting, while the other tested lacquers on beech-veneered panels and tested oils on solid beech were considered medium-emitting. Among the tested solid wood species ash, beech, oak and spruce were low/medium emitting and pine high-emitting. It should be taken into account that it is different types of chemical compounds that are emitted depending on wood species and type of surface treatment. Reduction of Hazardous Effects Modification/substitution of materials should be made when the emission contains toxicological unknown chemical substances. Materials and products should as far as possible not contain chemical substances with carci- nogenic effect, reproductive toxicity or allergy. Should this be the case these substances should be replaced with substances or materials, which are less hazardous or the material should at least be modified to minimize the con- tent as much as possible. Modification of materials and products should be considered for the mate rials and products with relatively large S-values and high indoor-relevant time-values. Modification/Substitution Examples Factors of importance for modification/substitution considerations have been systematized and applied on six examples of wood and wood-based materials and products. Examples, which have been based on a theme for inspiration for modification/substitution considerations, illustrate primary relations of importance for the impact of materials in the indoor environment. Further environment a.o. working environment and economics should be involved, where these are of decisive importance for the modification/substitution, and if their consequences are known. Descriptions of the product in relation to a given application as well as general and specific comments elaborates the conside rations. The six examples of substitution/modification considerations for wood furniture and wood-based building products comprise: A wooden floor surface treated with different types of lacquer and oil; wardrobe of veneered panel surface treated with different types of transparent lacquer; coffee table of untreated solid wood and respectively veneered panel surface treated with different types of transparent lacquer; bookcase of untreated solid wood and respectively veneered panel surface treated with different types of transparent lacquer; office table of veneered panel surface treated with different types of transparent lacquer and a house of pine. Finally, a proposal is given for a model for relative description of materials of the similar type exempli- fied for wooden floor surface treated with different lacquers and oils. Report in English Additional descriptions, results and evaluations in details are given in an extensive report in English: "Emission of Volatile Organic Compounds from Wood and Wood-based Materials".
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