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Anthropogenic sources[edit]
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- Chlorofluorocarbons and chlorocarbons[edit]
- Methylene chloride[edit]
- Regulation of indoor VOC emissions[edit]
- Limit values for VOC emissions[edit]
- Chemical fingerprinting[edit]
Anthropogenic sources[edit]Anthropogenic sources emit about 142 teragrams of carbon per year in the form of VOCs.[11] Specific components[edit]Paints and coatings[edit]A major source of man-made VOCs are coatings, especially paints and protective coatings. Solvents are required to spread a protective or decorative film. Approximately 12 billion litres of paints are produced annually. Typical solvents are aliphatic hydrocarbons, ethyl acetate, glycol ethers, and acetone. Motivated by cost, environmental concerns, and regulation, the paint and coating industries are increasingly shifting toward aqueous solvents.[16] Chlorofluorocarbons and chlorocarbons[edit]Chlorofluorocarbons, which are banned or highly regulated, were widely used cleaning products and refrigerants. Tetrachloroethene is used widely in dry cleaning and by industry. Industrial use of fossil fuels produces VOCs either directly as products (e.g., gasoline) or indirectly as byproducts (e.g., automobile exhaust).[citation needed] Benzene[edit]Main article: Benzene One VOC that is a known human carcinogen is benzene, which is a chemical found in environmental tobacco smoke, stored fuels, and exhaust from cars. Benzene also has natural sources such as volcanoes and forest fires. It is frequently used to make other chemicals in the production of plastics, resins, and synthetic fibers. Benzene evaporates into the air quickly and the vapor of benzene is heavier than air allowing the compound to sink into low-lying areas. Benzene has also been known to contaminate food and water and if digested can lead to vomiting, dizziness, sleepiness, rapid heartbeat, and at high levels, even death may occur.[citation needed] Methylene chloride[edit]Methylene chloride is another VOC that is highly dangerous to human health. It can be found in adhesive removers and aerosol spray paints and the chemical has been proven to cause cancer in animals. In the human body, methylene chloride is converted to carbon monoxide and a person will suffer the same symptoms as exposure to carbon monoxide. If a product that contains methylene chloride needs to be used the best way to protect human health is to use the product outdoors. If it must be used indoors, proper ventilation is essential to keeping exposure levels down.[citation needed] Perchloroethylene[edit]Perchloroethylene is a volatile organic compound that has been linked to causing cancer in animals. It is also suspected to cause many of the breathing related symptoms of exposure to VOCs.[citation needed] Perchloroethylene is used mostly in dry cleaning. While dry cleaners recapture perchloroethylene in the dry cleaning process to reuse it, some environmental release is unavoidable. Studies show that people breathe in low levels of this VOC in homes where dry-cleaned clothes are stored and while wearing dry-cleaned clothing.[citation needed] MTBE[edit]MTBE was banned in the US around 2004 in order to limit further contamination of drinking water aquifers primarily from leaking underground gasoline storage tanks where MTBE was used as an octane booster and oxygenated-additive.[citation needed] Indoor air[edit]Main article: Indoor air quality Since many people spend much of their time indoors, long-term exposure to VOCs in the indoor environment can contribute to sick building syndrome.[17] In offices, VOC results from new furnishings, wall coverings, and office equipment such as photocopy machines, which can off-gas VOCs into the air.[18][19] Good ventilation and air-conditioning systems are helpful at reducing VOCs in the indoor environment.[18] Studies also show that relative leukemia and lymphoma can increase through prolonged exposure of VOCs in the indoor environment.[20] There are two standardized methods for measuring VOCs, one by the National Institute for Occupational Safety and Health (NIOSH) and another by Occupational Safety and Health Administration (OSHA). Each method uses a single component solvent; butanol and hexane cannot be sampled, however, on the same sample matrix using the NIOSH or OSHA method.[21] The aromatic VOC compound benzene, emitted from exhaled cigarette smoke is labeled as carcinogenic, and is ten times higher in smokers than in nonsmokers.[18] The United States Environmental Protection Agency (EPA) has found concentrations of VOCs in indoor air to be 2 to 5 times greater than in outdoor air and sometimes far greater. During certain activities indoor levels of VOCs may reach 1,000 times that of the outside air.[22] Studies have shown that individual VOC emissions by themselves are not that high in an indoor environment, but the indoor total VOC (TVOC) concentrations can be up to five times higher than the VOC outdoor levels.[23] New buildings especially, contribute to the highest level of VOC off-gassing in an indoor environment because of the abundant new materials generating VOC particles at the same time in such a short time period.[17] In addition to new buildings, we also use many consumer products that emit VOC compounds, therefore the total concentration of VOC levels is much greater within the indoor environment.[17] VOC concentration in an indoor environment during winter is three to four times higher than the VOC concentrations during the summer.[24] High indoor VOC levels are attributed to the low rates of air exchange between the indoor and outdoor environment as a result of tight-shut windows and the increasing use of humidifiers.[25] Regulation of indoor VOC emissions[edit]In most countries, a separate definition of VOCs is used with regard to indoor air quality that comprises each organic chemical compound that can be measured as follows: Adsorption from air on Tenax TA, thermal desorption, gas chromatographic separation over a 100% nonpolar column (dimethylpolysiloxane). VOC (volatile organic compounds) are all compounds that appear in the gas chromatogram between and including n-hexane and n-hexadecane. Compounds appearing earlier are called VVOC (very volatile organic compounds) compounds appearing later are called SVOC (semi-volatile organic compounds). See also these standards: ISO 16000-6, ISO 13999-2, VDI 4300-6, German AgBB evaluating scheme, German DIBt approval scheme, GEV testing method for the EMICODE. Some overviews over VOC emissions rating schemes [26] have been collected and compared. France and Germany have enacted regulations to limit VOC emissions from commercial products, and industry has developed numerous voluntary ecolabels and rating systems, such as EMICODE,[27] M1,[28] Blue Angel[29] and Indoor Air Comfort[30] In the United States, several standards exist; California Standard CDPH Section 01350[31] is the most popular one. Over the last few decades, these regulations and standards changed the marketplace, leading to an increasing number of low-emitting products: The leading voluntary labels report that licenses to several hundreds of low-emitting products have been issued (see the respective webpages such as MAS Certified Green.- Certified Products[32]). Formaldehyde[edit]Many building materials such as paints, adhesives, wall boards, and ceiling tiles slowly emit formaldehyde, which irritates the mucous membranes and can make a person irritated and uncomfortable.[18] Formaldehyde emissions from wood are in the range of 0.02 – 0.04 ppm. Relative humidity within an indoor environment can also affect the emissions of formaldehyde. High relative humidity and high temperatures allow more vaporization of formaldehyde from wood-materials.[33] Health risks[edit]Respiratory, allergic, or immune effects in infants or children are associated with man-made VOCs and other indoor or outdoor air pollutants.[34] Some VOCs, such as styrene and limonene, can react with nitrogen oxides or with ozone to produce new oxidation products and secondary aerosols, which can cause sensory irritation symptoms.[18][35] Unspecified VOCs are important in the creation of smog.[36] Health effects include eye, nose, and throat irritation; headaches, loss of coordination, nausea; damage to liver, kidney, and central nervous system. Some organics can cause cancer in animals; some are suspected or known to cause cancer in humans. Key signs or symptoms associated with exposure to VOCs include conjunctival irritation, nose and throat discomfort, headache, allergic skin reaction, dyspnea, declines in serum cholinesterase levels, nausea, vomiting, nose bleeding, fatigue, dizziness.[citation needed] The ability of organic chemicals to cause health effects varies greatly from those that are highly toxic, to those with no known health effects. As with other pollutants, the extent and nature of the health effect will depend on many factors including level of exposure and length of time exposed. Eye and respiratory tract irritation, headaches, dizziness, visual disorders, and memory impairment are among the immediate symptoms that some people have experienced soon after exposure to some organics. At present, not much is known about what health effects occur from the levels of organics usually found in homes. Many organic compounds are known to cause cancer in animals; some are suspected of causing, or are known to cause, cancer in humans.[37] Reducing exposure[edit]To reduce exposure to these toxins, one should buy products that contain Low-VOCs or No VOCs. Only the quantity which will soon be needed should be purchased, eliminating stockpiling of these chemicals. Use products with VOCs in well ventilated areas. When designing homes and buildings, design teams can implement the best possible ventilation plans, call for the best mechanical systems available, and design assemblies to reduce the amount of infiltration into the building. These methods will help improve indoor air quality, but by themselves they cannot keep a building from becoming an unhealthy place to breathe.[citation needed] Limit values for VOC emissions[edit]Limit values for VOC emissions into indoor air are published by e.g. AgBB, AFSSET, California Department of Public Health, and others. These regulations have prompted several companies to adapt with VOC level reductions in products that have VOCs in their formula, such Benjamin Moore & Co. in the paint industry and Weld-On in the adhesive industry.[citation needed] Chemical fingerprinting[edit]The exhaled human breath contains a few hundred volatile organic compounds and is used in breath analysis to serve as a VOC biomarker to test for diseases such as lung cancer.[38] One study has shown that "volatile organic compounds ... are mainly blood borne and therefore enable monitoring of different processes in the body."[39] And it appears that VOC compounds in the body "may be either produced by metabolic processes or inhaled/absorbed from exogenous sources" such as environmental tobacco smoke.[38][40] Research is still in the process to determine whether VOCs in the body are contributed by cellular processes or by the cancerous tumors in the lung or other organs. VOC sensors[edit]Main article: VOC sensors VOCs in the environment or certain atmospheres can be detected based on different principles and interactions between the organic compounds and the sensor components. There are electronic devices that can detect ppm concentrations despite the non-selectivity. Others can predict with reasonable accuracy the molecular structure of the volatile organic compounds in the environment or enclosed atmospheres[41] and could be used as accurate monitors of the Chemical Fingerprint and further as health monitoring devices. Solid-phase microextraction (SPME) techniques are used to collect VOCs at low concentrations for analysis.[42] See also[edit]
References[edit]
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