VOCS: volatile organic compounds, or VOCs, are carbon-containing organic chemicals—many of which can be present in indoor in low concentrations. Indoor sources include building materials, furnishings, consumer products, tobacco smoke, and indoor chemical reactions (spontaneous chemical reactions between oxidants such as ozone and various common indoor chemicals in indoor air or on indoor surfaces). VOCs from attached buildings such as auto repair shops and dry cleaners may also enter indoor living spaces, as can outdoor air, also a source of pollutants containing VOCs. VOCs may be odorous and some VOCs are known or suspected to cause a variety of adverse health effects.
VOCs and Sensory Irritation Symptoms or Sick Building Syndrome Symptoms: Sensory irritation symptoms, which include irritation of eyes, nose, throat, and skin, are frequently reported by occupants as linked to their periods of occupancy in specific buildings. There is significant and increasing evidence that VOCs sometimes cause sensory irritation symptoms; however, the current evidence is insufficient for firm conclusions. Most individual VOCs are probably not present at a sufficient concentration in the air of typical buildings to cause sensory irritation symptoms themselves. Formaldehyde is the best documented exception to this. Mixtures of multiple VOCs, which can include specific highly irritant VOCs that are produced by indoor chemical reactions, appear likely to be sources of irritation in buildings at some times. Initial evidence is appearing that concentrations of some specific VOCs may be related to the occurrence in buildings of a broader set of symptoms, such as respiratory symptoms, headaches, and fatigue, sometimes called Sick Building Syndrome symptoms. The actual mechanisms for these possible effects are unknown.
VOCs and Allergy, Asthma, and Related Respiratory Symptoms: There have been four substantial review articles addressing the association of higher concentrations of VOCs in indoor air with allergies, asthma, and related adverse respiratory health symptoms. Three out of four reviews, and a majority of the more recently published papers, find significant evidence of linkages between some VOCs and these health effects. The evidence of a linkage of formaldehyde with allergies, asthma, and respiratory effects is most extensive.
VOCs in Cleaning/Sanitizing Products and Health: There is substantial evidence that individuals whose occupations include regular cleaning activities in buildings have an increased risk of adverse respiratory health effects and asthma. There is limited evidence that increased non-work-related use of household cleaning sprays by home occupants increases the risks of the same health effects. Because cleaning activities will often simultaneously increase exposures to VOCs and non-VOC pollutants, the links of cleaning work to adverse respiratory health effects are not necessarily a consequence of cleaning-related exposures to VOCs.
Implications for Good Building Practices: While there are many uncertainties about the health risks of indoor VOCs, the evidence of health risks is clearly sufficient to warrant that precautionary measures be taken to limit VOC exposures. Eliminating or limiting the indoor sources of VOCs is the first option to consider. In some cases, sources can be easily eliminated or reduced through behavior changes or product substitutions, while in other cases source reduction measures are complicated and require tradeoffs. Increased ventilation is often easier to apply than source control, and ventilation simultaneously reduces concentrations of many VOCs; however, ventilation in many situations increases a building's energy use and will often result in smaller reductions in indoor VOC concentrations than can be achieved with VOC source control. One reason for this is that, for some compounds like formaldehyde, benefits of increased ventilation can be partly offset by increased emissions. Increased ventilation will not be highly effective in reducing airborne concentrations of semi-volatile organic compounds (SVOCs) which have a higher molecular weight than VOCs and are present mostly on indoor surfaces.