Occupational Health Category vs. Occupational Exposure Limit
An occupational health category (OHC), or sometimes called an occupational hazard category or an occupational exposure band (OEB), is an assignment of an early stage compound to a range of airborne concentrations in which a compound should be handled. The term OHC is often used interchangeably with the term occupational exposure band (OEB).
OHC (a.k.a. OEBs) serve to communicate to the end users what the degree of potential occupational hazard exists with a specific compound, and it is based solely on the toxicology of the active pharmaceutical ingredient. In addition, OHC (OEB) serve to assist management in their risk assessment for determining the strategy on how much control (ventilation, containment, procedures, PPE, etc.) is needed. If you control to above the top of the range, you're potentially overexposing your employees and it's risky. Controlling to below the bottom of the OHC band is needless, time-consuming, and expensive.
While we would like to have a one-to-one relationship between the OHC and the necessary controls, that is not always the case. A risk assessment is what links the two together. For example, a secondary packaging organization that is handling an OHC 4 compound would not necessarily need to use Control Band 4 engineering controls since a detailed risk assessment would indicate that the probability of exposure or cross-contamination is low; therefore, the overall risk would be low.
Depending on the specific company, OHC assignments can be as follows:
- 1 to 4
- 1, 2, 3a, 3b, 4
- 1, 2, 3, 3+, 4, 5
- 1 to 5
- and many others.
It is very important to recognize that there is NO universally adopted system. The number of OHC bands depends upon whatever system the specific company has adopted (see Figure 1.)
On the other hand, occupational exposure limits (OEL) are the numerical value of the maximum airborne concentration (typically expressed in micrograms/cubic meter) of an active pharmaceutical ingredient, for which it is believed, that any worker can be exposed to day-after-day, for an entire working lifetime, without the expectation of any significant adverse health effect.
When a compound is in early stage development, it is typically assigned to an OHC because there is a lot of uncertainty in the data. Once the toxicology data set becomes more complete and reliable, then the expert toxicologists will develop a specific numerical occupational exposure limit.
Do OHCs contain a numerical OEL?
Yes, but the numerical OEL is based on the OEL for the bottom of the control band. Once more data becomes publicly available a more robust OEL must be developed.
Do OHCs contain the ADE?
Yes, but the ADE is an estimate based on the bottom of the control band multiplied by the human variability factor for workers (in most case 5).
