VOCs: Definition, Sources, and Health Effects
Efforts to reduce traffic-caused particulate matter pollution in cities are paying off nationwide in Germany: reports of declining particulate matter concentrations are becoming more frequent. Despite this good news, there is no all-clear when it comes to air pollution. The reason: volatile organic compounds, or VOCs for short.
In a recent study, Carnegie Mellon University (Pittsburgh, USA), in cooperation with the National Oceanic and Atmospheric Administration (NOAA, USA), focused on volatile organic compounds, VOCs and compared detailed chemical measurements of outdoor air in Los Angeles with indoor air quality data. They concluded that air pollution in the USA is only about half attributable to traffic-related particulate matter emissions. VOCs from industrial and consumer products are responsible for the other half.
Definition: Volatile Organic Compounds
Volatile organic compounds (VOCs) is the umbrella term for all organic, i.e. carbon-containing, substances that evaporate quickly (i.e. volatilize) due to their low boiling point. They exist as a gas even at relatively low temperatures, for example at room temperature, but can also be vapor-form – that is, both liquid and gaseous. The most common substance groups include hydrocarbons, aldehydes, alcohols, and organic acids.
The World Health Organization (WHO) divides the group of VOCs by their boiling point, and thus by their respective volatility, into the following subgroups:
- < 0 to 50… 100°C → Very Volatile Organic Compound (VVOCs)
- 50…100°C to 240…260°C → Volatile Organic Compound (VOCs)
- 240…260 to 380…400°C → Semi-Volatile Organic Compound (SVOCs)
- > 380°C → Particle-Bound Organic Matter (POMs, organic matter bound to particulate matter)
Giving an exact definition of VOCs is difficult, however. Some definitions are based on vapor pressure, others base their classification on the photochemical reactivity of the compounds and thus their significance as precursor substances for the formation of ground-level ozone. In addition, some definitions explicitly exclude certain organic substances from the substance group. For example, NMVOC (Non-Methane Volatile Organic Compounds) excludes methane (CH4).
The sum of all VOCs present in indoor air is also referred to as TVOCs (total Volatile Organic Compounds). Creating TVOC as an indicator metric is what first makes it possible to assess VOC concentration in a room. Nevertheless, this simplification remains problematic, since grouping together different chemical compounds cannot do justice to the complexity of their reactions and effects. For this reason, it also remains difficult to set limit values for TVOC.
Sources of VOCs
Biological sources of volatile organic compounds include decay, decomposition, and plant metabolic processes. These compounds accumulate in outdoor air. The same applies to VOCs from technical processes, such as those arising from incomplete combustion (e.g. vehicle exhaust) or from certain commercial and industrial activities.
Indoors, VOCs frequently arise from off-gassing of building materials and the entire interior fit-out. This includes flooring, walls, and ceilings, but also paints, varnishes, and adhesives, as well as furniture, home accessories, and often toys. In addition, there are numerous cleaning, care, and hobby products, as well as flame retardants, tobacco smoke, food preparation, and finally the metabolic processes of residents.
Since Europeans predominantly spend their time indoors, the volatile organic compounds present there are of greater significance to health and performance.
Health effects: irritation, fatigue, headaches
An elevated VOC concentration first shows up as a changed perception of smells and tastes. In addition, irritation of the mucous membranes and eyes can occur. The higher the concentrations rise, the stronger these symptoms become. Fatigue and headaches can also occur.
If these symptoms typically decrease after leaving a polluted room, especially after a longer absence, and increase again upon re-entering, this could be what's known as Sick Building Syndrome (SBS). This syndrome describes the occurrence of certain symptoms and illnesses that cannot be attributed to specific causes. What's characteristic, however, is that they're linked to staying in a building.
There are currently too few conclusive studies on the long-term effects of exposure to volatile organic substances. However, experts suspect a connection between VOCs and the increase in allergic reactions, especially in toddlers and infants. Constant contact with fragrances can also trigger allergies. Furthermore, experts consider the long-term toxic effects of many of these substances to be potentially carcinogenic, mutagenic, and reproductively harmful.
Improving air quality
To keep exposure to volatile organic substances as low as possible, the products and materials chosen should be low-emission. The Blue Angel eco-label is, for example, a good indicator of such products. For construction and renovation work, the AgBB evaluation scheme (established by the Committee for Health-Related Evaluation of Building Products) helps find especially low-VOC materials.
Since the composition of a room's TVOCs varies just as much as the toxicity of the individual substances, it's difficult in this case to give concrete, generally applicable advice. It's therefore necessary to continuously monitor pollutant concentrations in living and working spaces. Only this way can the sources of VOC emissions be reliably identified. This also determines whether the measured substances (e.g. those arising from cooking) are relatively harmless or whether they're toxic and thus acutely hazardous to health.