Air Quality

Senses Involved in Air Quality Judgment

Our sense of olfaction contributes to our evaluation of air quality by imparting sensations of intensity, (un) pleasantness, character (e.g., whether the odor smells solvent-like or putrid), and identity (“This is diesel fuel”). In addition, many airborne chemicals give rise to feelings of burning and stinging in the eyes, nose, or upper airways associated with the common chemical sense (chemesthesis). Both senses contribute to a person's evaluation of air quality. For example, air quality will be judged as bad when a person smells ammonia while feeling a sting up the nose during work.

Health Effects and Contributing Factors

We distinguish between indoor air quality and outdoor air quality. The air quality out of doors can be bad near highways, in industrial areas, and near animal operations. Indoor air quality may be jeopardized in offices as a result of bad ventilation, in the workplace when working with organic solvents, or at home and in schools because of fumes from carpet glue or building materials.

Depending on the chemical and its concentration, people may experience health effects from exposure such as sensory irritation of the eyes, nose, and throat; respiratory problems; or even central nervous system effects such as losing consciousness. Exposure to toxic substances at work can damage the olfactory epithelium—where the odor receptors are located—and diminish a person's sense of smell. On the other hand, decreased [Page 37]odor sensitivity to chemicals as a result of occupational exposure may also be the result of adaptation. Often, the situation reverses after exposure has discontinued.

We speak of direct health effects, such as described earlier, when people report health effects that are in line with toxicological models concerning the relation between health effects and chemical concentration. Yet, complaints about air quality and associated symptoms cannot always be explained scientifically. This may be the case when chemical concentrations cannot be measured with detection instruments, or are too low to account for the reported effects. This may be explained by individual variability in sensitivity because some people can pick up certain smells at much lower concentrations than other people can—or detection instruments—and yet others are sensitive because of allergic conditions or asthma.

Health effects may also be indirect consequences of chemical exposure, in the sense that the effects are mediated by the perception or interpretation of the odor. For example, when people smell an unpleasant odor near a factory, they may interpret that odor as a warning signaling harm, and react accordingly. Such reactions may involve a stress response, which causes physiological changes in the body leading to increases in blood pressure, heart rate, and sweating. In this manner, health effects that were really brought on by stress associated with perception of odor as threat can be mistakenly attributed to the chemical composition of the odorous air.

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