Food Environment and Health

Volatile Organic Compounds (VOCs)

Volatile organic compounds (VOCs) are emitted as gases from certain solids or liquids. VOCs include a variety of chemicals, some of which may have short- and long-term adverse health effects. VOCs are emitted by a wide array of products numbering in the thousands. Examples include: paints and lacquers, paint strippers, cleaning supplies, pesticides, building materials and furnishings, office equipment such as copiers and printers, correction fluids and carbonless copy paper, graphics and craft materials including glues and adhesives, permanent markers, and photographic solutions.

The term volatile organic compounds resfers to those organic compounds which are present in the atmosphere as gases, but which under normal conditions of temperature and pressure would be liquids or solids. A volatile organic compound is by definition an organic compound whose vapour pressure at say 20^oC is less than 760 torr (101,3 kPa) and greater than 1 torr (0,13 kPa). Other terms used to represent VOCs are hydrocarbons (HCs), reactive organic gases (ROGs), and non-methane volatile organic compounds (NMVOCs).

Unlike traditional major air pollutants (e.g. CO, SOx, NOx) volatile organic compounds contain mixtures of numerous organic subtances with variable content and are emmited from a variety of sources. For practical purposes VOC emissions may be grouped according to traditional chemical categories such as non-halogenated organic compounds (alkanes, alkenes, aromatics, alcohols, aldehydes, ketones and ester) and halogenated organic compounds (halogenated hydrocarbons and other other halogenated organics). However, such a classification might be misleading because the health and environmental effects of specific VOC do not necessarily correlate with these categories.

Volatile organic compounds (VOCs) are released to the environment from a variety of outdoor and indoor sources. Indoor releases of VOCs result from indoor activities such as cooking, use of office machines, releases from building materials, consumer products, as well as tobacco smoke. In some cases, vehicular emissions can also lead to indoor contamination directly in houses that have attached garages. Outdoor releases are due to combustion of fuels, fugitive emissions from petrochemical and chemical facilities, VOC emission from public-owned treatment works, mobile sources, and product use and disposal. EPA estimates that about 32% of the nationwide VOC emission are from mobile sources, while 17% is attributed to direct industrial processing and production activities.

EPA's Office of Research and Development's "Total Exposure Assessment Methodology (TEAM) Study" (Volumes I through IV, completed in 1985) found levels of about a dozen common organic pollutants to be 2 to 5 times higher inside homes than outside, regardless of whether the homes were located in rural or highly industrial areas. TEAM studies indicated that while people are using products containing organic chemicals, they can expose themselves and others to very high pollutant levels, and elevated concentrations can persist in the air long after the activity is completed.

The ability of organic chemicals to cause health effects varies 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.

An exhaustive literature survey of the emission of VOCs from plants is available. Generally, deciduous trees are mainly isoprene emitters and coniferous trees monoterpene emitters, though some plants are both isoprene and monoterpene emitters of isoprene and monoterpene emitters (e.g. Sitka spruce) or do not emit at all.

The distribution of VOCs in the multimedia environment will vary with topographical and meteorological parameters, the physicochemical properties of the environmental media, and properties of the VOCs. For example, soil properties such as fraction of organic carbon, moisture content, and pH affect sorption of organic pollutants by the soil matrix. Another example is the increase in bioconcentration af hydrophobic organic chemicals in biota with increasing lipid content. The parttioning of VOCs among the different environmental compartments are also governed by the physicochemical properties of the pollutants of interest including partition coeffecients, biotransfer factors, and intermedia transport parameters (for example, mass transfer coeeficient).

For steps to reduce exposure, increase ventilation when using products that emit VOCs. Meet or exceed any label precautions. Do not store opened containers of unused paints and similar materials within the school. Formaldehyde, one of the best known VOCs, is one of the few indoor air pollutants that can be readily measured. Identify, and if possible, remove the source. If not possible to remove, reduce exposure by using a sealant on all exposed surfaces of paneling and other furnishings. Use integrated pest management techniques to reduce the need for pesticides.

REFERENCES

EPA. United States Environmental Protection Agency. 2012. An Introduction to Indoor Air Quality (IAQ). Volatile Organic Compounds (VOCs).  Washington, DC.

Richard G. Derwent. 1995. Issues in Environmental Science and Technology. Cambridge CB4 4WF, UK.

S. Vigneron, J. Hermia, and J. Chaouki. 1994. Characterization and Control of Odours and Voc In The Process Industries. Netherlands.

Wuncheng Wang, Jerald L.Schnoor, and Jon Doi, editors. 1996. Volatile Organic Compounds in the Environment. Fredericksburg, VA.