To determine an employee's radon exposure, to which measurement should one refer?

The rationale for considering the highest pre-mitigation measurement combined with the time spent in the home is rooted in the fundamental principles of evaluating radon exposure. Radon exposure is ultimately determined by both the concentration of radon in the environment and the duration of time an individual spends in that environment.

The highest measurement provides insight into the worst-case scenario for exposure, indicating moments of peak radon concentration. When this is combined with the time spent in the home, it gives a comprehensive understanding of how much radon an employee could potentially be exposed to over a specific period. This approach is more reflective of true exposure risk compared to simply using average levels or lowest recorded levels, as radon is a variable gas that can fluctuate significantly based on numerous factors such as weather conditions, building ventilation, and seasonality.

Moreover, measurements taken during the first week of testing may not adequately represent long-term radon levels, as radon can change over time, and relying on such short-term assessments may not provide an accurate picture of exposure.

In summary, the correct answer effectively captures the essence of radon exposure assessment by emphasizing both the peak levels present and the actual time spent exposed, leading to a more accurate determination of an employee's exposure to radon.