Reciprocal Calculation Procedure (RCP) part 2: how to calculate an OEL based on RCP method

In this video we will explain how to calculate an OEL based on the RCP.
To learn more on what the RCP is and how this has evolved, watch our first video.
For the calculation, we take the example of the OEL calculation for a hypothetical aromatic solvent. First, we need to know the approximate composition of this hydrocarbon solvent, so that we match each constituent or range of constituents to a GGV or SSV.
If the solvent has 80% C9-C15 aliphatic constituents, this fraction is expressed as 0.8. she says “point eighty (0.8)”. It should be “point eight”.
Secondly, the GGV of C9-C15 aliphatics equals 1050 mg per cubic meter, is assigned to this fraction.
Thirdly, the fraction is divided by the GGV.
This is done for all other constituent’s fractions, to finally add them all up, and do the reciprocal of the sum to obtain the solvent’s calculated OEL.
For example, for a hypothetical aromatic solvent containing approximately 1.5% C8 aliphatics, 18% C9 aromatics, and 0.5% xylene, the added-up fraction is 1/OEL equals 1/0.0026 and the reciprocal is obtained which can be rounded up to a final OEL of four hundred mg/m3she reads out the reciprocal oel of 388.4. The number that is important is the rounded up number. So instead she could say, “”.
Although the RCP methodology has been adopted in some countries, like in Germany, the GGV are lower because of local methodological adaptations that have been applied when assessing the same database as the basis for the GGV.
These unnecessary adaptations inevitably deliver lower OELs for the same substance, which creates inconsistencies across Europe where the German methodology is not used.
Consideration should also be given when constituents are at unusually high concentrations that may result from blending activities, for example in solvents with more than 20% cyclohexane.
In these situations, the SSV (e.g. cyclohexane) should be used instead of the GGV.
These considerations are indicated in the calculator developed by HSPA.
Finally, the question remains which information should be communicated in the Safety Data Sheet. In this sheet, occupational advice must be clear and is included in section 8
.
Thus, although GGV and SSV are essential to calculate the overall hydrocarbon solvent OEL, these should not appear on the Material Safety Data Sheet, but rather the final RCP calculated value.
When there are constituents of concern that might be exceeded, such as cumene, these should be communicated as additional information.
We hope this video has been instructive. For further questions please contact [e-mail].