Volatile organic compounds
Volatile organic compounds (VOCs) are a diverse group of chemicals that easily evaporate into the air and can significantly impact both human health and environmental quality. They include both human-made and naturally occurring substances, such as acetone, benzene, formaldehyde, and toluene. VOCs are commonly found in various household products, including paints, cleaning supplies, and cosmetics, as well as in emissions from vehicles and industrial processes. High concentrations of VOCs, particularly indoors, can lead to health issues ranging from eye and throat irritation to more serious conditions like cancer.
Most VOCs are produced by plants, while the remaining are generated by human activities such as manufacturing and fuel combustion. Regulatory bodies, including the U.S. Environmental Protection Agency (EPA), monitor and manage VOC emissions due to their role in forming ground-level ozone and contributing to smog. Although many VOCs have distinct odors, some are odorless and can be difficult to detect. To mitigate exposure, individuals are encouraged to improve ventilation, reduce the use of VOC-emitting products, and consider air quality testing, particularly in newly constructed or remodeled buildings. Understanding VOCs, including their properties and effects, is essential for promoting better indoor air quality and health.
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Volatile organic compounds
Summary: Volatile organic compounds are a class of chemicals that can cause serious damage to health and are often regulated for their contribution to smog.
Volatile organic compounds (VOCs) include a variety of chemicals, both human-made and naturally occurring, that contain carbon and evaporate or sublime into the air more easily than less volatile compounds. Some common VOCs are acetone, benzene, ethylene glycol, formaldehyde, methylene chloride, and toluene. VOCs have high vapor pressures, so liquid VOCs evaporate quickly and solid VOCs can sublime relatively easily into a gaseous form at room temperature. VOCs can evaporate under normal indoor atmospheric conditions of temperature and pressure. The most volatile VOCs include propane, butane, and methyl chloride, while pesticides and fire retardants tend to be less volatile. Because they enter the air so easily, products with VOCs can have a strong impact on air quality, often with negative results for human health and the environment. VOCs are increasingly regulated, and there are a number of precautions individuals should take to limit exposure to harmful VOCs.
Roughly 90 percent of VOCs in the atmosphere are produced by plants. The remaining 10 percent are produced by humans in the manufacture of a wide range of chemical products and the burning of fuels such as gasoline, wood, coal, and natural gas. Many anthropogenic (human-produced) VOCs come from solvents, which make it easier to spread paint and other protective or decorative films. Chlorofluorocarbons, which were widely used as propellants, refrigerants, and solvents, were once a major source of VOCs but have been phased out in most countries since the Montreal Protocol took effect in 1989.
The US Environmental Protection Agency (EPA) regulates VOCs outdoors primarily because of their ability to create ozone and photochemical smog under certain conditions. Many VOCs form ground-level ozone by reacting with oxygen molecules in the atmosphere, often from nitrogen oxides (NOx) and carbon monoxide (CO), in the presence of sunlight. While ozone at higher altitudes helps to block harmful ultraviolet rays from the sun, reducing the risk of skin cancer, ground-level ozone can irritate the eyes, nose, and throat and is a harsh lung irritant. Ozone can also contribute to asthma and other respiratory conditions. A number of VOCs are exempted from regulation by the EPA because they are not considered reactive in the smog formation process. Some of these exempted chemicals, however, such as methylene chloride (used in paint strippers) and perchloroethylene (used in dry-cleaning fluid), could be highly toxic for human health if present indoors.
The EPA has found that levels of several VOCs average two to five times higher indoors. VOCs can be emitted by many household products, including cosmetics, aerosol sprays, paints, cleaning supplies, newly dry-cleaned clothing, laser printers, photocopiers, glues, permanent markers, moth repellants, air fresheners, and stored fuels. Certain activities, such as paint stripping, can increase levels of some VOCs temporarily by as much as 1,000 times background outdoor levels, and elevated concentrations can persist in the air long after the activity is completed. VOCs can also be emitted by new furnishings, wall coverings, furniture, ceiling tiles, vinyl flooring, adhesives, and carpeting.
Sick building syndrome refers to situations in which building occupants experience health effects that seem to be linked to time spent in a particular building. New buildings can have especially high VOC levels, because adhesives and other VOC-emitting building materials have not had sufficient time to off-gas. The World Health Organization released a report in 1984 in which it noted that up to 30 percent of new and remodeled buildings worldwide might be the subject of excessive complaints related to indoor air quality. Many VOCs can have direct adverse effects on human health, especially when they are found in high concentrations indoors, where most people spend the majority of their time (at home or at work). Americans, for example, spend roughly 90 percent of their time indoors. VOCs have been implicated in health effects ranging from irritations of the eyes, nose, and throat to cancer. They can also contribute to headaches, nausea, allergic skin reactions, fatigue, dizziness, and damage to the liver, kidneys, immune system, and central nervous system.
In addition to regulating VOCs that can contribute to smog and ozone, the EPA regulates VOCs under the Safe Drinking Water Act with regard to discharge into water sources. The US Department of Labor’s Occupational Safety and Health Administration (OSHA) also regulates some VOCs in the workplace. OSHA, for example, has adopted a permissible exposure level of 0.75 parts per million (ppm) for formaldehyde, perhaps the best-known and most notorious VOC, because it increases the risk of cancer. While no federal standards have been set in the United States for VOCs in nonindustrial indoor settings, the EPA advises that actions should be taken to reduce formaldehyde when it is present at levels higher than 0.1 ppm. California was the first state to enact laws limiting the VOC content in paints and coatings.
Many people can smell high levels of some VOCs, but other VOCs have no detectable odor. Although there is no method that can measure all VOCs present in an area, if high levels of VOCs are suspected, an air quality test can help identify possible sources. It may be especially useful to test buildings in the winter, when VOC concentrations can be much higher than during the summer.
Whether or not testing is a viable option, a number of precautions can be taken to reduce VOC concentration indoors. Integrated pest management techniques can help reduce or eliminate the need for pesticides. Ventilation should be maximized while using products that emit VOCs. Gases can leak from closed containers, so unused paints, gas canisters, and other VOC sources should not be stored in living areas.
Researchers are exploring the VOCs emitted by plants to understand their function. VOCs play a role in self-protection and transmission of information and vary by species, metabolic stage, and other factors. Researchers believe understanding plants' defensive mechanisms, including VOC release, can benefit conservation efforts.
Bibliography
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Koppmann, Ralf. Volatile Organic Compounds in the Atmosphere. Oxford: Wiley-Blackwell, 2007.
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"Volatile Organic Compounds." American Lung Association, 11 Apr. 2024, www.lung.org/clean-air/indoor-air/indoor-air-pollutants/volatile-organic-compounds. Accessed 7 Aug. 2024.
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