Volatile Organic Compounds or VOCs
In indoor air quality (IAQ) research, the term “volatile organic compound” refers to many thousands of carbon containing (organic) chemicals that, at room temperature, are present in the form of a gas. VOCs can be natural chemical compounds or made artificially by mankind.
VOCs come to our environment from many sources. Indoor VOC pollutants can come from materials used to build, as well as carpets, rugs and furnishings, cleaning products and personal care products, technical products like office equipment (especially photocopiers and laser printers), synthetic and natural air fresheners, pesticides, combustion processes such as tobacco smoking, burning of wood or kerosene, or cooking with natural gas or LPG stoves.
Current knowledge talks about the linkages of indoor VOCs with sensory irritation, allergies, asthma, and related respiratory effects, and cancer. We know that potential health effects of VOCs in cleaning products, SVOCs, and VOCs produced indoors from chemical reactions can be substantial.
Some VOCs and SVOCs have distinct and readily sensed odors. Some are suspected to create adverse health effects, which can range from sensory irritation symptoms, allergies and asthma, neurological and liver toxicity, through to cancer. Combined VOCs together may have effects that are greater or lower than the sum of their individual effects, and little scientific data is available on such combined effects.
Some of the key indoor sources of SVOCs are pesticides, building materials, and decorating materials. These latter two items can contain flexible plastics, like vinyl wallpaper or flooring. Building materials or furniture which contains flame retardants can also be a source of SVOCs.
For many VOCs and SVOCs for which the primary sources are indoors, the indoor air concentrations significantly exceed the outdoor air concentrations. The concentrations of VOCs due to indoor sources depend on materials in the environment as well as occupant behaviors and external contaminations that may enter the indoor space.
Part of the spectrum of VOCs can be envisioned via the following diagram:
VOCs include a very wide variety of types of molecules that can be categorized by structure, chemical bonds, function of parts of the molecules, or by specific elements (such as, for example, chlorinated hydrocarbons containing chlorine, hydrogen, and carbon–such ‘friendly’ compounds as dioxin, mustard gas and DDT are included here).
A subgroup of VOCs is called semi-volatile organic compounds or SVOCs that includes plasticizers, flame retardants, and pesticides. SVOCs are present partly as airborne gaseous chemicals and partly adsorbed on indoor surfaces or onto microscopic airborne or settled particles. SVOCs are often present largely attached to surfaces and particles, only a small fraction of them being in the air unattached to particles.
We measure VOC concentration in parts per billion (ppb), parts per million (ppm), or micrograms per cubic meter (µg/m3). A microgram is one one-millionth of a gram. One ppb of a VOC such as formaldehyde would represent 0.001 µg/m3. If our concentration of formaldehyde is 1 ppb, then for every billion molecules of air there is one molecule of formaldehyde. If the concentration of formaldehyde is 1 µg/m3, then for every cubic meter volume of air there is 1 microgram weight (mass) of formaldehyde.
When Xtox investigates indoor environments for air quality problems, we measure and report “total volatile organic compound” or “TVOC” concentrations. The term TVOC refers to the total concentration of multiple airborne VOCs simultaneously present in the air. TVOC methods measure a subset of VOCs that are expected to be present.
Xtox can also measure for concentrations of individual VOCs.
Analysis of materials used in a present dwelling, renovation or new construction can be engaged by Xtox, so as to get a better picture of the overall toxic threat that building work may present to the occupants. It is worthwhile to note that not all toxic VOCs are declarable items, and that harmful materials may be present in so called “low VOC” or even “zero VOC” (or ‘ZVOC’) labelled products. Thus, Knowledge of what is being missed in standard disclosures of product hazards can go a long way towards optimisation of the indoor environment for occupant health.
Formaldehyde is a common VOC which is widely used in the manufacture of building materials and numerous household products. It is also produced in combustion and other natural processes. Formaldehyde may be present in substantial concentrations both indoors and outdoors. Due to its widespread nature and significant health effects, Xtox devotes specific focus in its environmental assessments to formaldehyde.
Various organizations have established guidelines or recommendations for maximum formaldehyde concentration exposures. Despite differences in guidelines, the longer exposure periods (longer than 8 hours) consistently (and understandably) nominate lower guideline concentrations of formaldehyde (7-40 ppb) as compared to the guidelines for periods of 8 hours or less (44-750 ppb). An exception is the relatively high chronic guideline of 100 ppb from the World Health Organization (WHO). 100 ppb is currently seen by WHO and associated scientific authors to be protective against all short- and long-term health effects, including sensory irritation, cancer, and reproductive effects.