This is a big distinction when evaluating a workplace.

If you find an overexposure (or simply a real-exposure), then it is prudent, and expected, to look for employees with possible symptoms.

If employees have symptoms (especially those nondescript ones, like; nausea, dizzyness, and fatigue) it is much harder to say they have an exposure. You really can’t make that assumption without more information.

For example, if you have cancer, do you assume it is from all the bad food you ate during your lifetime? or, is from multiple factors? On the flip side, if you are a pile driver for 30 years and at the age of 60 you find that you have hearing loss, everyone assumes it’s from your job.

However, a lot of industrial hygiene work comes from “my employees have these symptoms”. The hard part is taking that information and determining if there is concern in the workplace.