Volatile organic compounds | Source of air pollution

Volatile organic compounds are characterized as those organic chemicals with huge vapor pressure at normal room temperature. This huge vapor pressure is as a development of a minor boiling point, which results as the causation of more molecules are evaporated from the surface of the solid or liquid compound and penetrates into the air to cause volatility.

Such as the formaldehyde with the boiling point of just -19° C is evaporated from the paint and extracted from the resin. There are many varying volatile organic compound which is present everywhere. These chemical compounds are present in nature and made by human.

Such as odors or scent are a volatile organic compound. Volatile organic compounds are important for the transfer of messages between plants and animals and also play a major role in transmission from plant to plant. Whoever the volatile organic compound is alarming to the health of human or also the causation of damage to the environment.

Exclusively indoor volatile organic compounds whose concentration is at the greatest level are governed by the law. Commonly adverse volatile organic compound increases the effect on health for a long time and are not extremely toxic. This is because their aggregation is commonly in low quantity and their symptoms are minor for their establishment.

How we can define volatile organic compounds?

In the US state agencies and Environmental Protection Agencies with the autonomous free air pollution arrangement contains the exception of volatile organic compound that is not reactive or having low reactivity in the compilation of the smog process.

Checking demand for volatile organic compounds is varying from state to state in the US. In California, the conclusion obtained by the south coast district of Air quality Management and California air resource board are more remarkable in the volatile organic compound arrangement.

The use of reactive organic gases by the California ARB for the measurement of organic gases after the conception of the public.

Biologically generated VOCs.

Methane ejects carbon 1150 teragrams in a year in the structure of volatile organic compounds. The major compound of volatile organic compounds is isoprene and more of its quantity is formed by the plants. The remnants are formed by microbes and plants.

The odor which is ejected by the plants also consists of leafy green volatiles and is influenced by the factors which are sunlight and temperature. 

The ejection of odor takes place in the stomata of the leaves. Most of the volatile organic compounds are terpenes. It provides a sense of scale in the area of Pennsylvania of the US state is 62000 km² and survey to eject 3,400,000 kilograms of terpenes in the growing season.

Anthropogenic sources volatile organic compounds

Carbon is ejected from the anthropogenic sources in the appearance of a volatile organic compound.

Specific components.

Paints and coatings

The main origin of the volatile organic compound which is made by man is coatings such as careful coatings and paints. The careful and embellishing film is dispersed by the solvent. Paints of 12 billion liters are formed in a year. Glycol ethers, acetone, ethyl acetate, and aliphatic hydrocarbon are common solvents. Due to environmental establishment and arrangement coating and paint industries

Chlorofluorocarbons and chlorocarbons.

Chlorofluorocarbon that is prohibited is used on a wide scale for the refrigerants and cleaning the product. Tetrachloroethene is used on a wide scale for dry cleaning.

Fossil fuel.

Fossil fuel is also used to form a product such as gasoline by directly or indirectly it is used as a byproduct such as automobile exhaust gas. Other such components such as benzene, methylene chloride, perchloroethylene, and formaldehyde.

If the volatile organic compound is exposed to the indoor environment it can be devoted to infected the building syndrome. A volatile organic compound is used in the coverings of the wall, new furnishing, and the equipment which is used in the office e.g photocopy machine.

There are two methods for the measurement of volatile organic compounds one is the national institute for occupational safety and health and the other is by OSHA.

A single component solvent is used for each method. The aromatic volatile organic compound such as benzene which is ejected from the cigarette smoke is known as carcinogen and it is ten times more smoker than nonsmokers. In the indoor environment, VOC concentration in winter is 3 to 4 times higher than the VOC concentration in summer.

Indoor air quality measurement.

The volatile organic compound measurement takes place with the sorption tubes in the indoor air such as Tenax or DNPH-cartridges. A volatile organic compound is adsorbed from the material and then it is desorbed thermally.

Indoor is used for the product ejecting of volatile organic compounds such as furniture and building product and they are examined in the emission test chamber in a checked climatic condition. If we determine the measurement for the quality control round robin test is performed.

Regulation of indoor VOC emissions.

In many countries, a different definition of the volatile organic compound is used. On the Tenax TA the adsorption of the volatile organic compound in the air, separation from gas chromatography on the 100% nonpolar column, and thermal desorption.

A volatile organic compound is a compound that is shown in the gas chromatogram in between the n-hexane and n-hexadecane. Compound that is shown in the prior is called a very volatile organic compound and compound that are shown in subsequent is called a semi-volatile organic compound.

Health risks due to volatile organic compounds

A man-made volatile organic compound such as respiratory, allergic aftereffect the infants and adults. Most of the volatile organic compound e.g limonene and styrene react with the ozone and nitrogen oxides to form the secondary aerosols and the oxidation of the product that is the causation of provocation symptoms.

Smog and tropospheric ozone are formed by the volatile organic compound. Provocation of the throat, nose, and eye, coordination loss, nausea, kidney, liver, and central nervous system damage. Organic chemicals which cause health effect are varying from more toxic to the less toxic health effect and rely upon many factors exposure level, and the time that it is exposed. Most of the organic compounds are able to cause cancer.

Reducing exposure VOCs

If we reduce the exposure of these toxins then we obtain the products with No VOCs or low-VOCs. When the design of building and homes is made the designing team use the best apparatus for ventilation plans and can reduce the infiltration from the building.

By this method, we advance the indoor air quality but by this method, the building becomes dragging to breathe.

Limit values for VOC emission.

California department of public health, AgBB, ASSET, and others published the limit values of VOC emission. This arrangement has eager the many companies of the adhesive and paint industries to modify the VOC level for the compression of the product. In a tinted paint if an ounce of color is added 5 to 20 g of VOC is present in it. 5 to 15 ounce of color is added in dark color and 300 or more grams of volatile organic compound is added in a gallon of paint.

Chemical fingerprinting.

A few thousand of VOC is also present in the exhaled breath consume for the breath biopsy to test for lung cancer. A volatile organic compound is also bloodborne and is able to monitor the processes of the body. It indicates that the volatile organic compound is formed either by metabolic processes such that environmental tobacco smoke.

Researchers are made to indicate that either the cell processes or cancerous tumors in the lung use the volatile organic compound in the body.

Principle and measurement method.

By the interaction in an organic compound and sensor components, a volatile organic compound in the environment is detected. Sometimes the odor of VOC is detected by the human nose as by the wine, coffee, and paper. Electronic devices that detect the concentration in ppm.

We can determine the accurate measurement of volatile organic compounds and their molecular structures in the atmosphere or environment and is used for the monitoring of chemical fingerprint and health monitoring devices.

In order to store the VOC at less concentration, a solid-phase microextraction technique is used for analysis purposes. For the measurement of a high concentration of VOC, a lower explosion limit is used. For the faster detection of VOC, direct injection of mass spectrometry technique is used.

For the on-line diagnose of anthropogenic and biogenic VOC. Recent a detection limit of 20 ppt is obtained after 1-minute measurement by PTR.MS instrument that is based on the time of flight mass spectrometry. The massive resolution of the devices is from 7000 to 10500 m/∆m, thus we can obtain the isobaric VOC and can obtain their quantity independently.

Accuracy and traceability of VOC

Metrology for VOC measurement.

For the measurement of VOC, a standard SI unit is used. If many oxygenated VOC is available monoterpenes no standard VOC is required this is because the adsorption of the molecules takes place.

On the lacking of the standard gas mixture at minimum level concentration various national metrology institutes are worked on this to improve the zero gas and minimize the adsorption process.

The final scope of the standard gas is traceability and stability and is according to the data quality object and is obtained by the WMO/GAW program.    

Reviewed by:
Dr. Muhammad Adnan Asghar (Ph.D.)

Chinese Academy of Sciences Fuzhou, Fujian

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