What are Volatile Organic Compounds (VOC)?
The abbreviation VOC stands for the group of volatile organic compounds. VOCs include substances of organic origin found in the air in gaseous and vaporous form. They include, for example, hydrocarbons, alcohols, aldehydes, and organic acids. Many solvents, liquid fuels, and synthetic substances can occur in the form of VOCs, as can numerous organic compounds which are formed in the course of biological processes. Many hundreds of individual compounds can be found in the air at any time.
Specialists distinguish between VOCs, very volatile organic compounds (VVOC), and semi-volatile organic compounds (SVOC). The sum of the concentrations of all VOCs gives the TVOC value (total volatile organic compounds).
What are the sources of VOCs?
VOCs arise from a broad range of different sources. Their presence in atmospheric air can be accounted for by biological processes, for example, metabolic processes in plants, putrefaction or decomposition. Further sources of VOCs in atmospheric air include technical processes in which substances are generated through incomplete combustion (especially in vehicular emissions), or as volatile by-products of industrial or commercial processes. Possible sources of VOCs in indoor air include products and materials for use in construction and interior decoration (for example floor, wall, and ceiling coverings, paints, varnishes, adhesives, or materials used in furniture and decorating). Also of significance are body care products, cleaning materials, and hobby products, as well as tobacco smoke, and even food preparation and human metabolic processes.
In comparison to the sources of VOCs in atmospheric air, those to be found in indoor air in central Europe are generally of substantially greater significance in respect of their impact on health, as most people in this region spend much of their time indoors. In addition, there is mostly greater proximity to the sources. VOCs from outside can also penetrate into buildings. As a rule, however, ventilation leads to a reduction of the original interior concentrations.
How are VOCs released into the air?
When solvents or liquid fuels evaporate, and liquid or paste-like products dry out, VOCs are set free in large amounts into the surrounding air. A less obvious phenomenon is the release of various associated substances, which are not strongly bound to the products. They can slowly disperse into the air from the product surface and are delivered in a constant stream from the inside of the product to its surface (material emission). This applies for example to residual solvents and building blocks in plastics (monomers), excipients such as plasticisers, solubilisers, antioxidants, stabilisers, and catalysts from production processes, as well as to associated substances such as aromatics, flame retardants, and biocides. Terpenes are typical VOCs: they are released into the air from materials and products of natural origin, for example, wood. VOCs also arise as reaction products, for example, between oxygen, ozone or water and natural substances of content, such as those to be found in wood and vegetable oils.
What health impacts can VOCs have?
Normally the concentration levels of individual VOCs are very low and represent no risk to health. In the German Environmental Study, the Federal Environment Agency has drawn up a representative overview of those VOCs which occur in homes in Germany. Concentrations which might possibly cause adverse health effects can arise as a direct result of construction or comprehensive renovation work, or through improper work processes or the massive use of inappropriate products. Smell nuisances, irritations, and symptoms which cannot directly be attributed to a particular disease have been described as acute health problems in people. Such effects and more important chronic effects, which scientists have derived from toxicological assessments, must be avoided. This also applies especially for carcinogenic, genotoxic, and teratogenic effects. If such effects have already been attributed to particular substances, then, according to the Regulation on Hazardous Substances, these may no longer be used in end products. What cannot be completely excluded, however, is the possibility that VOCs with similar potential effects may be found in traces in a product, if they were either present in unchecked preliminary products or in recycled materials. A working group at the Federal Environment Agency has come up with guideline values for some frequently occurring VOCs with special significance in terms of their potential impacts on health.
How can the quantity of VOCs be reduced?
Consumers should choose products and materials which are particularly low in emissions. They can use environmental labels such as the Blue Angel to help them. If they are intending to undertake more comprehensive building or renovation work, they can check whether the materials they wish to use have been assessed according to the evaluation procedure developed by the AgBB (Committee for Health-related Evaluation of Building Products). If materials with an accredited environmental label are used or those that meet the criteria set by the Committee for Health-related Evaluation of Building Products, then it can be ensured that any possible release of VOCs into the environment will be at a very low level.
If health problems with a suspected link to VOCs arise at home, the quest to get to the source is usually a very difficult one. Measurements of indoor air and emissions in respect of different materials are very expensive and often do not deliver the clarity of answer that was hoped for. Residents in this position should therefore seek expert advice. They will find experts via local health and environment offices, the local Chamber of Industry and Commerce, or online. Specialists can often determine the probable cause of the VOC emission just by inspecting the residence and asking questions of those living in it. Once the sources of VOC contamination have been established, individual decisions need to be made as to their removal – according to the type and extent of possible deleterious health impacts, the level of VOC concentration and any reduction expected, and the costs involved. Here, too, specialist help should be sought to determine whether or how the VOC sources are to be removed, contained, or treated. As a general principle it is always a good idea to minimise the level of VOC concentration by means of ventilation of interior spaces.