An industrial hygienist asked OSHA two questions: whether the General Industry Lead and Cadmium standards are intentionally more restrictive by not allowing the performance option or objective data for repeat compliance monitoring across multiple shifts (as the Respirable Crystalline Silica and Chromium VI standards do), and whether professional judgment can be used to decide what constitutes representative samples applicable to multiple shifts across all four standards.
On the first question, OSHA answered yes — the older standards really are more restrictive. The agency explained that OSHA had not envisioned the use of the performance option for repeat monitoring at the time its older standards were promulgated. The performance option in newer standards (Silica, Chromium VI, and Beryllium) gives employers greater flexibility than the Lead standard issued in 1978 or the Cadmium standard issued in 1992 (29 CFR 1910.1025, 1910.1026, 1910.1027, 1910.1053).
On professional judgment, OSHA accepts it for evaluating objective and historical data — but only when such use is permitted by the particular OSHA standard applicable to the workplace. The agency emphasized that the burden is on the employer to demonstrate that the data meet the parameters specified for objective/historical data in the pertinent standards, and pointed to its Silica compliance guide and a 2006 letter to the American Bakers Association on chromium exposure assessments as reference points.