Volatile organic compound
Overview
 
Volatile organic compounds (VOCs) are organic chemicals that have a high vapor pressure
Vapor pressure
Vapor pressure or equilibrium vapor pressure is the pressure of a vapor in thermodynamic equilibrium with its condensed phases in a closed system. All liquids have a tendency to evaporate, and some solids can sublimate into a gaseous form...

 at ordinary, room-temperature
Room temperature
-Comfort levels:The American Society of Heating, Refrigerating and Air-Conditioning Engineers has listings for suggested temperatures and air flow rates in different types of buildings and different environmental circumstances. For example, a single office in a building has an occupancy ratio per...

 conditions. Their high vapor pressure results from a low boiling point, which causes large numbers of molecules to evaporate or sublimate from the liquid or solid form of the compound and enter the surrounding air. An example is formaldehyde
Formaldehyde
Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...

, with a boiling point of –19 °C (–2 °F), slowly exiting paint
Paint
Paint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...

 and getting into the air.

Many VOCs are dangerous to human health or cause harm to the environment
Natural environment
The natural environment encompasses all living and non-living things occurring naturally on Earth or some region thereof. It is an environment that encompasses the interaction of all living species....

.
Encyclopedia
Volatile organic compounds (VOCs) are organic chemicals that have a high vapor pressure
Vapor pressure
Vapor pressure or equilibrium vapor pressure is the pressure of a vapor in thermodynamic equilibrium with its condensed phases in a closed system. All liquids have a tendency to evaporate, and some solids can sublimate into a gaseous form...

 at ordinary, room-temperature
Room temperature
-Comfort levels:The American Society of Heating, Refrigerating and Air-Conditioning Engineers has listings for suggested temperatures and air flow rates in different types of buildings and different environmental circumstances. For example, a single office in a building has an occupancy ratio per...

 conditions. Their high vapor pressure results from a low boiling point, which causes large numbers of molecules to evaporate or sublimate from the liquid or solid form of the compound and enter the surrounding air. An example is formaldehyde
Formaldehyde
Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...

, with a boiling point of –19 °C (–2 °F), slowly exiting paint
Paint
Paint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...

 and getting into the air.

Many VOCs are dangerous to human health or cause harm to the environment
Natural environment
The natural environment encompasses all living and non-living things occurring naturally on Earth or some region thereof. It is an environment that encompasses the interaction of all living species....

. VOCs are numerous, varied, and ubiquitous. They include both man-made and naturally occurring chemical compounds. VOCs play an important role in communication between plants. Anthropogenic VOCs are regulated by law, especially indoors, where concentrations are the highest. VOCs are typically not acutely toxic, but instead have compounding long-term health effects. Because the concentrations are usually low and the symptoms slow to develop, research into VOCs and their effects is difficult.

Definitions

Diverse definitions of the term VOC are in use.

The definitions of VOCs used for control of precursors of photochemical smog used by EPA, and U.S. States with their own outdoor air pollution regulations include exemptions for VOCs that are determined to be non-reactive, or of low-reactivity in the smog formation process. EPA formerly defined these compounds as Reactive Organic Gases (ROG) but changed the terminology to VOC.

In the USA, different regulation exists per state - most prominent is the VOC regulation by SCAQMD and by California ARB. However, this specific use of the term VOCs can be misleading, specifically when applied to indoor air quality
Indoor air quality
Indoor air quality is a term referring to the air quality within and around buildings and structures, especially as it relates to the health and comfort of building occupants....

 because many chemicals that are not regulated for controlling outdoor air pollution can still be important for indoor air pollution - there is no correlation between VOC content in a product and VOC emissions from that product into indoor air.

Canada

Health Canada
Health Canada
Health Canada is the department of the government of Canada with responsibility for national public health.The current Minister of Health is Leona Aglukkaq, a Conservative Member of Parliament appointed to the position by Prime Minister Stephen Harper.-Branches, regions and agencies:Health Canada...

 classes VOCs as organic compounds that have boiling points roughly in the range of 50 to 250 °C (122 to 482 F). The emphasis is placed on commonly encountered VOCs that would have an effect on air quality.

European Union

A VOC is any organic compound having an initial boiling point less than or equal to 250 °C measured at a standard atmospheric pressure of 101.3 kPa and can do damage to visual or audible senses.

US

VOCs (or specific subsets of the VOCs) are legally defined in the various laws and codes under which they are regulated. Other definitions may be found from government agencies investigating or advising about VOCs. The United States Environmental Protection Agency
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...

 (EPA) regulates VOCs in the air, water, and land. The Safe Drinking Water Act
Safe Drinking Water Act
The Safe Drinking Water Act is the principle federal law in the United States intended to ensure safe drinking water for the public. Pursuant to the act, the Environmental Protection Agency is required to set standards for drinking water quality and oversee all states, localities, and water...

 implementation includes a list labeled "VOCs in connection with contaminants that are organic and volatile." The EPA also publishes testing methods for chemical compounds, some of which refer to VOCs.

In addition to drinking water, VOCs are regulated in discharges to waters (sewage treatment and stormwater disposal), as hazardous waste, but not in non industrial indoor air. The United States Department of Labor
United States Department of Labor
The United States Department of Labor is a Cabinet department of the United States government responsible for occupational safety, wage and hour standards, unemployment insurance benefits, re-employment services, and some economic statistics. Many U.S. states also have such departments. The...

 and its Occupational Safety and Health Administration (OSHA) regulate VOC exposure in the workplace. Volatile organic compounds that are hazardous material would be regulated by the Pipeline and Hazardous Materials Safety Administration
Pipeline and Hazardous Materials Safety Administration
The Pipeline and Hazardous Materials Safety Administration was created under the Norman Y. Mineta Research and Special Programs Improvement Act of 2004. United States president George W. Bush signed the legislation into law on November 30, 2004...

 while being transported.

Biologically generated VOCs

Not counting methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

, biological sources emit an estimated 1150 teragrams of carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

 per year in the form of VOCs. The majority of VOCs are produced by plants, the main compound being isoprene
Isoprene
Isoprene , or 2-methyl-1,3-butadiene, is a common organic compound with the formula CH2=CCH=CH2. Under standard conditions it is a colorless liquid...

. The remainder are produced by animals, microbes, and fungi, such as molds.

The strong odor emitted by many plants consists of VOCs. Emissions are affected by a variety of factors, such as temperature, which determines rates of volatilization and growth, and sunlight, which determines rates of biosynthesis
Biosynthesis
Biosynthesis is an enzyme-catalyzed process in cells of living organisms by which substrates are converted to more complex products. The biosynthesis process often consists of several enzymatic steps in which the product of one step is used as substrate in the following step...

. Emission occurs almost exclusively from the leaves, the stomata in particular. A major class of VOCs is terpene
Terpene
Terpenes are a large and diverse class of organic compounds, produced by a variety of plants, particularly conifers, though also by some insects such as termites or swallowtail butterflies, which emit terpenes from their osmeterium. They are often strong smelling and thus may have had a protective...

s, such as myrcene. Providing a sense of scale, a forest 62,000 km2 in area (the U.S. state of Pennsylvania) is estimated to emit 3,400,000 kilograms of terpenes on a typical August day during the growing season. Induction of genes producing volatile organic compounds, and subsequent increase in volatile terpenes has been achieved in maize using (Z)-3-Hexen-1-ol and other plant hormones.

Anthropogenic sources

Anthropogenic
Anthropogenic
Human impact on the environment or anthropogenic impact on the environment includes impacts on biophysical environments, biodiversity and other resources. The term anthropogenic designates an effect or object resulting from human activity. The term was first used in the technical sense by Russian...

 sources emit about 142 teragrams of carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

 per year in the form of VOCs.

Paints and coatings

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 liters of paints are produced annually. Typical solvents are aliphatic hydrocarbons, ethyl acetate
Ethyl acetate
Ethyl acetate is the organic compound with the formula CH3COOCH2CH3. This colorless liquid has a characteristic sweet smell and is used in glues, nail polish removers, and cigarettes...

, glycol ethers, and acetone
Acetone
Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...

. Motivated by cost, environmental concerns, and regulation, the paint and coating industries are increasingly shifting toward aqueous solvents
Aqueous solution
An aqueous solution is a solution in which the solvent is water. It is usually shown in chemical equations by appending aq to the relevant formula, such as NaCl. The word aqueous means pertaining to, related to, similar to, or dissolved in water...

.

Chlorofluorocarbons and chlorocarbons

Chlorofluorocarbon
Chlorofluorocarbon
A chlorofluorocarbon is an organic compound that contains carbon, chlorine, and fluorine, produced as a volatile derivative of methane and ethane. A common subclass are the hydrochlorofluorocarbons , which contain hydrogen, as well. They are also commonly known by the DuPont trade name Freon...

s, 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
Gasoline
Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...

) or indirectly as byproducts (e.g., automobile exhaust).

MTBE

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.

Indoor air

Since people today spend most of their time at home or in an office, long-term exposure to VOCs in the indoor environment can contribute to sick building syndrome
Sick building syndrome
Sick building syndrome is a combination of ailments associated with an individual's place of work or residence. A 1984 World Health Organization report into the syndrome suggested up to 30% of new and remodeled buildings worldwide may be linked to symptoms of SBS...

. In offices, VOC results from new furnishings, wall coverings, and office equipment such as photocopy machines, which can off-gas
Outgassing
Outgassing is the release of a gas that was dissolved, trapped, frozen or absorbed in some material. As an example, research has shown how the concentration of carbon dioxide in the Earth's atmosphere has sometimes been linked to ocean outgassing...

 VOCs into the air. Good ventilation and air-conditioning systems are helpful at reducing VOC emissions in the indoor environment. Studies also show that relative leukemia
Leukemia
Leukemia or leukaemia is a type of cancer of the blood or bone marrow characterized by an abnormal increase of immature white blood cells called "blasts". Leukemia is a broad term covering a spectrum of diseases...

 and lymphoma
Lymphoma
Lymphoma is a cancer in the lymphatic cells of the immune system. Typically, lymphomas present as a solid tumor of lymphoid cells. Treatment might involve chemotherapy and in some cases radiotherapy and/or bone marrow transplantation, and can be curable depending on the histology, type, and stage...

 can increase through prolonged exposure of VOCs in the indoor environment.

There are two standardized methods for measuring VOCs, one by the National Institute for Occupational Safety and Health
National Institute for Occupational Safety and Health
The National Institute for Occupational Safety and Health is the United States’ federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the Centers for Disease Control and Prevention within the U.S...

 (NIOSH) and another by Occupational Safety and Health Administration
Occupational Safety and Health Administration
The United States Occupational Safety and Health Administration is an agency of the United States Department of Labor. It was created by Congress of the United States under the Occupational Safety and Health Act, signed by President Richard M. Nixon, on December 29, 1970...

 (OSHA). Each method uses a single component solvent; butanol
Butanol
Butanol or butyl alcohol can refer to any of the four isomeric alcohols of formula C4H9OH:*n-Butanol, butan-1-ol, 1-butanol, n-butyl alcohol;*Isobutanol, 2-methylpropan-1-ol, isobutyl alcohol;...

 and hexane
Hexane
Hexane is a hydrocarbon with the chemical formula C6H14; that is, an alkane with six carbon atoms.The term may refer to any of four other structural isomers with that formula, or to a mixture of them. In the IUPAC nomenclature, however, hexane is the unbranched isomer ; the other four structures...

 cannot be sampled, however, on the same sample matrix using the NIOSH or OSHA method.
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. 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. 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. 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.

VOC concentration in an indoor environment during winter is three to four times higher than the VOC concentrations during the summer. 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

Regulation of indoor VOC emissions

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 http://www.product-testing.eurofins.com/ecolabels.aspx have been collected and compared.

France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 and Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 have enacted regulations to limit VOC emissions from commercial products, and industry has developed numerous voluntary ecolabels and rating systems, such as EMICODE, M1, Blue Angel and Indoor Air Comfort In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, several standards exist; California Standard CDPH Section 01350 is the most popular. 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).

Formaldehyde

Many building materials such as paints, adhesives, wall boards, and ceiling tiles slowly emit formaldehyde
Formaldehyde
Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...

, which irritates the mucous membranes and can make a person irritated and uncomfortable. 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.

Health risks

Respiratory, allergic, or immune effects in infants or children are associated with man-made VOCs and other indoor or outdoor air pollutants.

Some VOCs, such as styrene and limonene
Limonene
Limonene is a colourless liquid hydrocarbon classified as a cyclic terpene. The more common D isomer possesses a strong smell of oranges. It is used in chemical synthesis as a precursor to carvone and as a renewably-based solvent in cleaning products....

, can react with nitrogen oxides or with ozone to produce new oxidation
products and secondary aerosols, which can cause sensory irritation symptoms. Unspecified VOCs are important in the creation of smog.

Health effects include:
Eye, nose, and throat irritation
Throat irritation
Throat irritation is a common complaint in individuals of all ages. Throat irritation means different things to different people. Some people may mean a dry cough; others describe it as a scratchy feeling at the back of the throat and others simply mean a sensation of something stuck at the back of...

; 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
Dyspnea
Dyspnea , shortness of breath , or air hunger, is the subjective symptom of breathlessness.It is a normal symptom of heavy exertion but becomes pathological if it occurs in unexpected situations...

, declines in serum cholinesterase
Cholinesterase
In biochemistry, cholinesterase is a family of enzymes that catalyze the hydrolysis of the neurotransmitter acetylcholine into choline and acetic acid, a reaction necessary to allow a cholinergic neuron to return to its resting state after activation.-Types:...

 levels, nausea, emesis, epistaxis, fatigue, dizziness.

The ability of organic chemicals to cause health effects various'

s greatly from those that are highly toxic, to those with no known health effect. 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.

Limit values for VOC emissions

Limit values for VOC emissions into indoor air are published by e.g. AgBB, AFSSET, California Department of Public Health, and others.

Chemical fingerprinting

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
Lung cancer
Lung cancer is a disease characterized by uncontrolled cell growth in tissues of the lung. If left untreated, this growth can spread beyond the lung in a process called metastasis into nearby tissue and, eventually, into other parts of the body. Most cancers that start in lung, known as primary...

. One study has shown that "volatile organic compounds ... are mainly blood borne and therefore enable monitoring of different processes in the body." 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. 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.

VOCs Sensors

VOCs in the environment or certain atmospheres can be detected based in 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 and could be used as accurate monitors of the Chemical Fingerprint and further as health monitoring devices.

See also

  • Aroma compound
    Aroma compound
    An aroma compound, also known as odorant, aroma, fragrance or flavor, is a chemical compound that has a smell or odor...

  • Criteria air contaminants
    Criteria air contaminants
    Criteria air contaminants , or criteria pollutants, are a set of air pollutants that cause smog, acid rain and other health hazards. The laws and regulations of different polities may define different sets. CACs are typically emitted from many sources in industry, mining, transportation,...

  • Dutch standards
    Dutch standards
    Dutch Standards are environmental pollutant reference values used in environmental remediation, investigation and cleanup....

  • Fugitive emissions
    Fugitive emissions
    Fugitive emissions are emissions of gases or vapors from pressurized equipment due to leaks and various other unintended or irregular releases of gases, mostly from industrial activities. As well as the economic cost of lost commodities, fugitive emissions contribute to air pollution and climate...

  • NMVOC
    NMVOC
    NMVOC is the abbreviation for non-methane volatile organic compounds.It is a generic term for a large variety of chemically different compounds, like for example, benzene, ethanol, formaldehyde, cyclohexane, 1,1,1-trichloroethane or acetone....

     (non-methane volatile organic compounds)
  • Organic compound
    Organic compound
    An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

  • Photochemical smog
  • Volatility (chemistry)
    Volatility (chemistry)
    In chemistry and physics, volatility is the tendency of a substance to vaporize. Volatility is directly related to a substance's vapor pressure. At a given temperature, a substance with higher vapor pressure vaporizes more readily than a substance with a lower vapor pressure.The term is primarily...

  • NTA Inc
    NTA Inc
    NTA Inc is a nationally recognized testing laboratory and third party certification agency headquartered in Nappanee, Indiana, USA.- About NTA :NTA evaluates and certifies products for the residential and commercial building industry....

     VOC Testing Laboratory
  • Volatile Organic Compounds Protocol
    Volatile Organic Compounds Protocol
    The Protocol to the 1979 Convention on Long-Range Transboundary Air Pollution Concerning the Control of Emissions of Volatile Organic Compounds or Their Transboundary Fluxes is an agreement to provide for the control and reduction of emissions of volatile organic compounds in order to reduce their...

  • Ozone
    Ozone
    Ozone , or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope...


External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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