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VOCs – or volatile organic compounds to give them their full name – are organic chemicals with a high vapor pressure at room temperature. Their low boiling point causes a large number of molecules to evaporate into the atmosphere where they can cause harm to human health or the environment.
Volatile Organic Compounds
In the European Union, VOCs are defined as any organic compound with an initial boiling point less than or equal to 250 °C at atmospheric pressure. This definition covers a wide range of activities involving solvents including printing, vehicle coating and dry cleaning.
VOCs can be man-made or naturally occurring compounds and are found everywhere. Biologically generated sources include isoprene which is produced by plants, plus other VOCs from animals and microbes. Anthropogenic sources are much more varied, and generally more harmful to the environment and human health. Examples of anthropogenic VOCs include:
- Solvents used in paints and coatings to aid the spreading of protective or decorative layers. These are often aliphatic hydrocarbons, glycol ethers and acetone.
- Formaldehyde is also found in paints, adhesives, wall boards and ceiling tiles.
- Chlorofluorocarbons and chlorocarbons – many CFCs are now banned or highly regulated while tetrachloroethene is used in dry cleaning and industry.
- Perchloroethylene is also used in dry cleaning; it is often captured for reuse but some environmental release is inevitable. It is linked to causing cancer in animals.
- Fossil fuels, either directly as gasoline, or indirectly as exhaust gas
- Benzene, a known human carcinogen, is found in tobacco smoke, stored fuels and car exhausts. It is also often used to synthesize other chemicals in the production of plastics, resins and synthetic fibres.
- Methyl chloride is used in adhesive removers and aerosol spray paints.
Potential Hazards of Volatile Organic Compounds
Some sectors of the population are more likely to be exposed to VOCs than others. VOCs are hazardous to those in the petrochemical and oil and gas industries, as well as the chemical and paint industries. Those in the building trade are also likely to be at a greater risk as many building products, such as paints, solvents and glues give off VOCs. VOC vapors are flammable at low concentrations and are considered toxic even at low levels. For this reason, workers often have to monitor their exposure using Time Weighted Average (TWA) to ensure they are not overexposed to toxicity over a given time span.
It can be difficult to research the health and environmental effects of VOCs as their concentrations are often low and adverse symptoms slow to develop, and the extent and nature of the health effect is dependent on many factors including the level of exposure and the length of time exposed to it. However, there are some well known health risks. Respiratory, allergic or immune effects in the young are associated with man-made VOCs as well as other indoor and outdoor pollutants. Other symptoms include eye, nose and throat irritation, headaches, loss of coordination and nausea and in severe cases, damage to the liver, kidneys and central nervous systems. Some VOCs like perchloroethylene are suspected to cause cancer in animals while others have been linked to or are known to cause cancer in humans, like benzene.
Uses of Volatile Organic Compounds in Medical Field
However, while many VOCs are known to cause health issues, research has shown that VOCs can also be used to detect illnesses such as cancer, cystic fibrosis, chronic obstructive pulmonary disease, asthma and diabetes. In this instance, VOCs found in exhaled breath, or in bodily fluids such as blood, urine, feces or sweat, are used as a biomarker for the assessment or detection of disease. It works on the premise that different patterns of VOCs correlate with various diseases – the hypothesis is that pathological processes occurring as a result of disease either generate new VOCs not normally produced in the body or alter the concentration of those are. Indeed, studies have revealed that cancer cells in vitro produce or consume specific VOCs that act as potential biomarkers that differentiate it from noncancerous cells for example.
It is incredibly important to detect and monitor VOCs as such man-made chemicals present a danger to human health. However, research has shown that certain VOCs found in the body can be useful in detecting health issues, an area that could prove fruitful in the future.
References and Further Reading