OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.


Ms. Carol A. Chojnacki, CIH, MS
IH Source LLC
13180 Winterberry Way
New Berlin, Wisconsin 53151

Dear Ms. Chojnacki,

Thank you for your letter to the Occupational Safety and Health Administration’s (OSHA) Directorate of Enforcement Programs. You have questions related to compliance monitoring required by OSHA’s lead, hexavalent chromium, cadmium, and respirable crystalline silica standards and the use of professional judgement to evaluate objective/historical data. This letter constitutes OSHA's interpretation only of the requirements discussed and may not be applicable to any question not delineated within your original correspondence. Your paraphrased questions and our responses are below.

Background: In your letter, you state that the term “objective data” has been discussed to different degrees in OSHA’s Chromium (VI) (29 CFR 1910.1026), Cadmium (29 CFR 1910.1027), and the Respirable Crystalline Silica (29 CFR 1910.1053) standards. You state also that the Chromium (VI) standard and the Respirable Crystalline Silica standard use the term “performance option” and allow employers to use any combination of air sampling data, historical data, or objective data to determine employee exposures. Further, you note that the Lead in General Industry standard, which was promulgated before the Cadmium, Chromium (VI), and Respirable Crystalline Silica standards, does not address objective data or the performance option.

Finally, you assert that employers should also be able to use objective data to describe second- or third-shift exposures in situations where the work is essentially identical from one shift to the next, especially for routine compliance monitoring where sampling of all shifts has been done initially. You do not think such use of first-shift data could be made if different operations are done on other shifts (e.g., a foundry’s shakeout is only done on second shift). In that case, an employer would have to monitor on both the first and second shifts to sample the different operations and that a thorough analysis of the jobs on each shift must always be done before the sampling plan is determined.

Question 1: Does OSHA intend that its Lead in General Industry and Cadmium standards be more restrictive by not allowing the use of a performance option and/or objective data that is allowed by the Respirable Crystalline Silica standard and Chromium (VI) standard, when considering repeat compliance monitoring across multiple shifts?

Response: Yes, because OSHA had not envisioned the use of the performance option for repeat monitoring at the time its older standards were promulgated. The intent of the performance option in OSHA’s standards for Silica and Chromium (VI), as well as in its most-recently issued standard for Beryllium (29 CFR 1910.1024), is to give employers more flexibility to characterize employee exposures than OSHA provided in its older standards like Lead in General Industry (29 CFR 1910.1025), which was issued in 1978, and Cadmium (29 CFR 1910.1027), which was issued in 1992. 

Question 2: Would OSHA allow the use of professional judgement in evaluating objective/ historical data and applicable documentation in determining what would constitute representative samples that could be applied to multiple shifts? If so, could this practice be applied to all four of these standards, i.e., OSHA’s Respirable Crystalline Silica, Chromium (VI), Cadmium, and Lead standards?

Response: OSHA accepts application of professional judgement to evaluate any objective/ historical data and its supporting documentation to ensure that the data meet all definitions, criteria, and limitations identified by OSHA for such data and for representative sampling assessment, provided use of representative sampling and use of objective/historical data in lieu of monitoring is permitted by the particular OSHA standard(s) applicable to the workplace. When objective data are used to illustrate employee exposures, the burden is on the employer to demonstrate that the data meet the parameters specified for objective/historical data in the pertinent standards.

Some examples of using objective data to conduct exposure assessments for the Respirable Crystalline Silica standard under the performance option are listed on page 5 of OSHA’s Small Entity Compliance Guide for the Respirable Crystalline Silica Standard for General Industry and Maritime. A previous letter of interpretation by OSHA to the American Bakers Association, dated November 14, 2006, also provides guidance on the use of objective data to characterize employee exposures to hexavalent chromium.

Thank you for your interest in occupational safety and health. We hope you find this information helpful. OSHA’s requirements are set by statute, standards, and regulations. Our letters of interpretation do not create new or additional requirements but rather explain these requirements and how they apply to particular circumstances. This letter constitutes OSHA’s interpretation of the requirements discussed. From time to time, letters are affected when the Agency updates a standard, a legal decision impacts a standard, or changes in technology affect the interpretation. To assure that you are using the correct information and guidance, please consult OSHA’s website at www.osha.gov. If you have any further questions, please feel free to contact the Office of Health Enforcement at (202) 693-2190.



Kimberly Stille, Acting Director
Directorate of Enforcement Programs