Are these volatile organic compounds off-gassing into your indoor air?

Chemicals on which Wolverton focused in his plant air purification studies prominently included formaldehyde, and the BTX aromatics: benzene, toluene, and xylene. Formaldehyde occurs in plants and animals, and has been used as a preservative. The BTX aromatics are important components of petroleum products, including synthetic materials and plastics.

All of these chemicals have a somewhat pleasant odor. When inhaled, they enter the blood, and the breast milk of a nursing mother. They can remain in the body for just a few hours or, if one remains in a closed room, the dose may be continuous. The more the exposure, and the weaker the recipient’s immune system, the more the chance of developing cancer, breathing problems, or allergies.

Aldehydes

Aldehydes (same as ketones) are organic compounds which incorporate a carbonyl functional group (that’s C=O). The carbon atom of this group has two remaining bonds that may be occupied by hydrogen or alkyl or aryl substituents. If at least one of these substituents is hydrogen, the compound is an aldehyde. If neither is hydrogen, the compound is a ketone.

The majority of aldehydes and ketones have strong odors. Ketones generally have a pleasant smell and they are frequently found in perfumes (e.g. muscone in musk-smelling colognes). They are also used in food flavorings. Aldehydes vary in smell with most of the lower molecular weight smelling bad (rotten fruits), yet some of the higher molecular weight aldehydes and aromatic aldehydes smell quite pleasant and are thus used in perfumery.

Formaldehyde is the simplest aldehyde with a central carbon atom bound to two hydrogen atoms (H2C=O). Discovered in Russia by A. M. Butlerov in 1859 it is very reactive, used in dyes, medical drugs, insecticides and famously as a preservative and embalming fluid.

Source: What are Aldehydes?

BTX aromatics

Primary petrochemicals are divided into three groups depending on their chemical structure:

[One of these groups is known as the “Aromatics.” This group] includes benzene, toluene, and xylenes. Benzene is a raw material for dyes and synthetic detergents, and benzene and toluene for isocyanates MDI and TDI used in making polyurethanes. Manufacturers use xylenes to produce plastics and synthetic fibers.

Source: Wikipedia on classes of petrochemicals.

See also: Wikipedia on BTX chemistry.

Benzene

Benzene is a component of products derived from coal and petroleum and is found in gasoline and other fuels. Benzene is used in the manufacture of plastics, detergents, pesticides, and other chemicals.

Source: OSHA on Benzene.

Benzene’s use in consumer products has been limited due to its being a potent carcinogen. It is a very important component of gasoline, so that breathing gasoline vapor should be minimized.

In 1977, benzene was detected in outer space, by use of spectroscopy. Source: Wikipedia, on Benzene.

Toluene

Toluene is a non-water-soluble solvent which dissolves aldehydes. The odor of toluene is described thusly by blogger, Valerie Brown:

This mainstay of the chemical industry – a close relative of benzene – is in your hair dye, your concrete sealer, your gas tank; and it’s a glue sniffer’s siren song.

Source: Toluene: The Sweet Smell of Brain Damage.

The three Xylene isomers

Xylene, the third BTX aromatic, is very similar to benzene and toluene. The scent and products associated with Xylene are described as follows:

Xylene, also called xylol, dimethyl benzene, Violet 3, and methyl toluene, is an isomer that can be found in three forms [ortho – (or o –xylene), meta – (or m –xylene), and para – (or p –xylene)]. It is traditionally used in the leather, rubber, and paint industries, particularly as a solvent, a cleaning agent, and a paint thinner. Since it naturally occurs in petroleum, it is not surprising that it is also found in gasoline and jet fuel. It may also be considered a narcotic-type of drug, as it may be an intoxicant if it is inhaled.

Xylene is a highly-flammable, colorless liquid. Typically, it smells sweet, with a scent that is similar to balsam. It is usually refined through an alkylation process from crude oil, but it can also be made as a by-product from coal carbonization, extracted from benzole, or through the methylation of toluene.

There are many ways that xylene may be used. For example, it is sometimes used in making some polyester clothes and plastic bottles. In fact, nearly 50 percent of the xylene produced is used to produce polymers used in plastics and polyester. It is also used as a solvent in the paint and rubber industries. Some steel cleaning agents contain it as well.

Source: What Is Xylene?

These two air pollutants are created by human activity.

1. Ozone

Nitrogen is 78% of air, and oxygen is 21%. Ozone forms when oxides of nitrogen meet volatile organic chemicals, at the point where there has been an electrical charge, or sunlight, hitting VOCs. Here is how that process works:

NOx is a generic term for the mono-nitrogen oxides NO and NO2 (nitric oxide and nitrogen dioxide). They are produced from the reaction of nitrogen and oxygen gases in the air during combustion, especially at high temperatures. In areas of high motor vehicle traffic, such as in large cities, the amount of nitrogen oxides emitted into the atmosphere as air pollution can be significant. NOx gases are formed whenever combustion occurs in the presence of nitrogen.
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Oxygen and nitrogen do not react at ambient temperatures. But at high temperatures, they undergo an endothermic reaction producing various oxides of nitrogen.

Source: Wikipedia on Nitrogen oxide.

Ozone [in the upper atmosphere] is most commonly formed during electrical storms, where an electrical spark will cause the creation of a three-atom molecule. This ozone actually poses no human threat, as the gas’s existence is only dangerous if the concentration gathers at ground level.

Ozone on a ground level occurs when sunlight reacts with volatile organic compounds, which exist in sources such as hydrocarbon vehicle emissions.

Electrical sparks which create ozone may occur inside the home in any equipment which uses high voltage or ultraviolet light. These items include electric motors, high power office equipment (photocopiers or laser printers), or electronic air filters which have been improperly installed.

Source: How ozone is created

How does ozone become a part of smog?

Ground level or “bad” ozone is not emitted directly into the air, but is created by chemical reactions between oxides of nitrogen (NOx) (air is 78% nitrogen) and volatile organic compounds (VOC) in the presence of sunlight. Emissions from industrial facilities and electric utilities, motor vehicle exhaust, gasoline vapors, and chemical solvents are some of the major sources of NOx and VOC.

Source:The Environmental Protection Agency warns that ozone is a component of smog.

What are health risks of exposure to ozone?

Ozone is very harmful to the lungs. Exposure to ozone can make breathing difficult, inflame the lungs and lining of the respiratory tract, lead to permanent lung damage, and make it harder for the body to fight respiratory diseases. Symptoms to watch for include coughing, shortness of breath, and chest tightness/chest pain. In asthmatics, it can trigger asthma attacks and worsen symptoms. In people already in poor health, repeated exposure to high levels of ozone can increase the risk of dying.

Source: Ozone Generator Fact Sheet.

2, Carbon dioxide

The Environmental Protection Agency defines carbon dioxide as a volatile organic compound. See EPA fact sheet.

Carbon dioxide is a product of human respiration. In a sealed environment, the carbon dioxide content of air will rise, as humans breathe oxygen and exhale carbon dioxide. As the carbon dioxide content of air rises, the oxygen content of air, which is normally 21%, will decrease.

VOCs can be removed from air by mechanical means as well as by plants.

Commonly, ventilation systems function to exchange inside air for outside air. This manner of purifying air works well if the outside air is not polluted.

If a building is tightly sealed, plants can take over the process of extracting the VOCs from the air and replenishing oxygen, through the water byproduct of the plant’s transpiration.

Click next to review Kamal Meattle’s success with plants as botanical air purifiers in New Delhi, where outside air is too polluted for an air exchange ventilation system.