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Air pollutants: Volatile Organic Compounds

What are volatile organic compounds?

Volatile organic compounds, also known as VOCs, are organic chemical compounds with a high volatility under normal atmospheric temperature and pressure conditions. In other words, these organic compounds evaporate or sublimate easily at ordinary room temperature from materials and even organisms at low boiling points (according to experts definition, less than or equal to 250°C).

Any compound of carbon participating in atmospheric photochemical reactions is considered a VOC, excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides (or carbonates) and ammonium carbonate.

volatile organic compounds

Volatile organic compounds list

VOCs are numerous, varied and ubiquitous, both human-made and naturally occurring. For instance, most commonly found VOCs are:

  • Acetone CH3(CO)CH3
  • Benzene C6H6
  • Ethylene glycol C2H6O2
  • Formaldehyde CH2O
  • Methylene chloride CH2Cl2
  • Perchloroethylene C2Cl4
  • Toluene C7H8
  • Xylene C8H10
  • Trichloroethylene C2HCl3

VOCs classification

According to the World Health Organization (WHO), volatile organic compounds are categorized in the following:

  • Very volatile organic compounds (VVOCs): with a boiling point range from 0 to 50-100°C. Some examples are propane, butane or methyl chloride.
  • Volatile organic compounds (VOCs): having boiling points between 50-100 and 240-260°C. Examples of VOCs are toluene, ethanol, acetone or hexanal.
  • Semi-volatile organic compounds (SVOCs): boiling point from 240-260 to 380-400°C, the most typical compounds are pesticides or fire retardants.  

Volatile organic compounds sources

VOCs can be generated both biologically and anthropogenically. While anthropogenic sources emit about 142 teragrams of carbon per year as VOCs, biological sources produce about 1150 teragrams.

Plants are major producers of volatile organic compounds, but the emissions depend on some factors, such as sunlight (that determines biosynthesis rates) and temperature (that determines volatilization and growth). Plants eject all these emissions using their leaves, specifically the stomata.

We have many products at home that release or “off-gas” VOCs. Some examples of anthropogenic sources are: carpets, adhesives, composite wood products, paints, varnishes, air fresheners, cleaning and disinfecting chemicals, newspapers, non-electric space heaters, photocopiers, smoking, cosmetics, refrigerants, pesticides, gasoline or exhaust from cars, among many others.

VOCs in paint

Paints and protective coating are human-made major sources of VOCs, a disturbing fact giving that over 12 billion litres of paints are produced every year.

Currently, the United States Environmental Protection Agency (EPA) has constrained VOC content on paints at 250 grams per liter for flat coatings and 380 g/l for other coatings (such as low-luster or semi gloss). However, some states have adopted toughest measures, for instance California, with a limit of 50 g/l for all finishes.

vocs in paint

However, how long do VOCs last after painting? It depends on several factors: if these are outdoors or indoors, temperature, paint’s concentration of VOC content, house airflow, volume of the room or space, etc. For these reasons, measurement methods for VOCs indoors are not accurate and have led to several misunderstanding and criticism, as not everybody knows you need an expert to properly analyze it.

Since it is difficult to know the real exposure of VOCs, it is recommended using no or low VOC paints. To be considered VOC-free (or zero-VOC), it cannot contain more than 5 g/l of VOCs. These eco paints are the best solutions to prevent air pollution from VOCs.

VOCs health and environmental effects

VOCs are also well-known carcinogens since these are found 2 to 5 times more indoors than outdoors, especially man-made VOCs that are the origin for some allergies and respiratory problems. Volatile organic compounds main health effects are:

  • Eye, nose and throat irritation
  • Headaches, loss of coordination and nauseas
  • Damage the liver, kidneys and the central nervous system.
  • Some organics can cause cancer in animals and some others are suspected or known to cause cancer in humans.

nose irritation

Since the inhalation of VOCs usually takes place indoors, short-term exposure can quickly drive to symptoms like conjunctival irritation, nose and throat discomfort, headache, allergic skin reaction, dyspnea, declines in serum cholinesterase levels, nausea, vomiting, nose bleeding, fatigue and dizziness.

VOCs are not considered criteria pollutants by themselves, but are an important part of Ozone’s creation, both tropospheric and ground-level. For this reason, these are not considered  criteria pollutants, as VOCs have not a direct impact on the environment.

However, VOCs indirectly produce smog by reactions between ozone (created by the combination with NOx, heat and sunlight) and other compounds, which can really damage the environment and threat humans lives.

What can you do to protect yourself?

Volatile organic compounds can be detected using VOC sensors. These electronic devices identify ppm concentrations based on interactions between the organic compounds and the sensor components. However, the sensitivity and selectivity of the device depends on the molecular structure of the VOC and its concentration.

air purifier

Other methods to protect yourself are devices such as air purifiers for VOCs. Moreover, to protect yourself from VOCs you can make changes in your alimentation routines, like organic gardening food and starting to eat healthy grown vegetables and fruits without usage of synthetic fertilizers, pesticides, herbicides, etc.

2 thoughts on “Air pollutants: Volatile Organic Compounds

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