Nonetheless, the patient's simple descriptors of the workplace, although not as precise as industrial hygiene measurements, can document airborne exposures. For dust exposure, it is particularly useful to ask whether cough or nasal discharge at the end of the day is colored by dust and whether work clothes are dust-laden by the end of the day. Aerosols may be dense enough to dampen skin or clothes. In addition, it is important to ascertain whether there is direct skin contact with chemicals or other work materials that may be sensitizers or toxins. 14 Skin absorption as an exposure route is often overlooked in history-taking.
Abnormal smells can also be an important, albeit crude, measure of exposure.
Olfactory fatigue , the diminished ability to sense an odor after ongoing exposure, is an important attribute of certain chemical vapors and gases with high exposure. Confined space is also an exposure factor. Targeted history taking can elicit, with a very few questions, a good picture of the general hygienic conditions of the workplace. One of the most important determinants of working conditions is simply the size of the workplace. Small employment sites are often associated with the worst hygienic conditions and may be the least likely to have any safety or health infrastructure or any likelihood of inspection by an external agency.