What are Total Fractional Values
A Total Fractional Value, or TFV, is the concentration of a hazardous ingredient divided by the generic concentration limit of that hazard for the ingredient(s).
Why are TFVs useful?
TFVs are useful because they show where a hazard (generally a Hazard classification) becomes applicable to a formulation.
To discuss TFVs, it is useful to do a quick run through some other aspects of the legislation.
In GHS regulations, a key method of determining hazards for a formulation is to take the ingredients, hazards and percentages and perform some calculations to calculate the overall hazards of the formulation.
With “cumulative” hazards, e.g. environmental, corrosive and irritant hazards, you need to add together all the relevant ingredients with the same (or related) hazards. For “noncumulative” hazards, e.g. sensitising, carcinogenic, the hazards do not add together, so the ingredient with the highest hazard contribution drives the hazard of the formulation.
A formulation carries a specific hazard if the sum (for cumulative hazards), or maximum (for noncumulative hazards) of the TFVs of the ingredients for the hazards is 1 or more.
Simple example of calculating a TFV
Imagine you have a formulation which contains several ingredients classified as H315 – Causes skin irritation. H315 is a cumulative hazard. Altogether there is 15% of H315 ingredients.
Should the formulation be classed as H315?
We look at the legislation to find out to trigger point. For H315, the general concentration trigger is 10%, that is, if 10% or more of a formulation’s relevant ingredients are classified as H315, and none of those ingredients have Specific Concentration Limits and there are no other ingredients which are relavnt, then the formulation will be classified as H315. So in this case, where we have 15% of H315 ingredients, the formulation is classified as H315.
Where do TFVs come in?
In the above H315 example, there were 15% H315 ingredients and the General Concentration Limit for H315 labelling is 10%. This can be expressed as a TFV in the following way:
TFV = Concentration / General Concentration Limit, so
TFV = 15/10 = 1.5
The TFV allows us to judge how near we are to the hazard being applied. A TFV of 0.99 would mean you were just underneath the threshold for a hazard to apply, a TFV of 1 means you are exactly at the point where it applies, a TFV of 1.5 means you are one and a half times the hazard contribution that requires the hazard to be applied.
For other types of hazard the General Concentration Limits are different. H351, Suspected of causing cancer, is a noncumulative hazard with a General Concentration Limit of 1% for CLP. So if any individual ingredient classified as H351 is present at 1% or above, the whole formulation must be classified as H351. IN OSHA GHS the limit is different at 0.1% – in this case, if any individual ingredient classified as H351 is present at 0.1% or above, the whole formulation must be classified as H351.
Please note that TFVs can get more complicated when there are Specific Concentration Limits and where there are cumulative hazards.
Also note that TFV <1 for all the hazards of a formulation does not necessarily mean that the formulation requires no hazard labelling. For example, sensitising ingredients may have to be declared on the label at low concentrations.
