It’s not just about Respirators
As an industrial hygienist I find the particular challenges of conducting exposure assessments fascinating. Many people tell be they would rather watch paint dry... more about paint later. Many clients tell me, we need to know what exposures should be assessed and which respirators make the most sense for our employees.
Lately, I have been involved in providing expert testimony in cases involving respiratory protection and worker exposure evaluations. The most recent case became so confused that the Judge queried me for nearly fifteen minutes regarding the rules surrounding respirators and employers’ responsibilities regarding conducting employee exposure determinations for airborne contaminates.
Afterwards, I thought to myself, if it is this confusing during a case before the Board of industrial Insurance Appeals how can we expect the average employer to understand… let alone comply with the law.
The use of any respirator should be based upon an accurate exposure assessment answering the question, how much airborne contaminate(s) will the employee be exposed? Only by an accurate exposure assessment can appropriate selection of respiratory protection be assured.
Let me give two (2) examples.
EXAMPLE 1: SILICA
Most of the time a negative pressure air-purifying respirator with HEPA cartridges is simply issued to a worker exposed to silica. However, in the Northwest, there are actually three (3) measurements that need to be taken when assessing airborne silica levels. Those measurements include:
Total respirable dust (unique monitoring required) PEL 5.0 mg/M3
Respirable silica (unique monitoring/analysis required) PEL 0.1mg/M3
Cristobalite (unique monitoring/analysis required) PEL 0.05 mg/M3
All three of these assessments can be accomplished simultaneously if the industrial hygienist and laboratory make appropriate preparations.
Ultimately, all three contaminates must be combined into a mixed contaminate assessment. In other words they are added together. The ten times (10x) protection factor (PF) for a half-face respirator may not be adequate.
EXAMPLE 2: PAINTS
The majority of time a half face negative pressure air-purifying respirator with organic cartridges with pre-filter/HEPA is given the worker exposed to paint mists/vapors. However, once again it is important to consider that the paint is typically a formulation of many hazardous chemicals. Exposure evaluations for paints should be unique permissible exposure limit (PEL) assessments referred to as fifteen (15) minute short term exposure limits or STELS. You might also have a unique chemical that requires a ceiling limit assessment.
Sampling for this type of exposure often results in multiple chemical assessment and analysis. The rule of law requires that all chemicals with a similar target organ must be combined. Similar to the Silica example where the target organ was the lung: if several solvents in a paint formulation have a similar target organ then they must be combined.
This is often referred to as a “mixed solvent” exposure assessment.
Exposure assessments do not need to be conducted for each and every exposure. Deciding what types of exposures and how many assessments need to be conducted is all part of a proactive safety program.