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  • Joe Winslow

Oral Solid Dosage (OSD) Facility, Dust Containment

One of the most important and vexing problems that OSD facilities deal with is dust containment. This containment is an issue from the point where the raw materials are first opened for sampling, all the way through the manufacturing and packaging process. Almost every single operational step must deal with dust containment at some level. Some operations, like dispensing, milling, or compression create high levels of dust, while others, like wet granulation or packaging create less. These operations however, must all contain dust to some degree.

When discussing containment of any kind, it is important to think about two things; what you are trying to protect, and what paths (vectors) the dust contaminant could take.

In a pharmaceutical environment, we are trying to protect 4 things:

1. The product (this includes the patient)

2. Operators, maintenance and other personnel

3. The environment

4. The business (reduced product waste).

The paths that dust contaminant can take include: Escape from the equipment, Transfer through the HVAC system, Physical transfer (on clothing and shoes), Escape through a waste stream (equipment and facility cleaning, dust collection, etc.).

Once this is determined, a matrix can be set up to do a risk assessment. Ask questions like “What escape vectors pose a risk to the Product, Personnel, Environment, and/or the Business?”, “What do those risks look like?”, etc. The risk assessment needs to look at the probability of each risk, the severity of the risk, and the probability of detection that an upset condition will be reached. There are numerous methodologies and tools that have been established to perform a formal risk assessment. These include FMEA, HAZOP, the Monte Carlo method, and others. Each of these methods will work, and each has pros and cons, but the method is less important than just performing the exercise.

As a result of the risk assessment, you will have a list of the various risks ranked in order from highest to lowest. You will then start with the highest risk and look at ways to mitigate it. Usually, a threshold value is set that defines which risks need mitigation. All those risks with a value higher than the threshold are evaluated for mitigation, those below the threshold are deemed acceptable risks that do not require mitigation.

As an example, let’s say the highest potential risk identified is dust migrating to other processing rooms, or to the atmosphere through the HVAC system. There are several mitigation strategies available that could be acceptable in an OSD facility.

First, you can seal the equipment better so that less or no dust escapes.This would be preferable to all other strategies because it protects all 4 of the things identified above that you want to protect.

Second, you could provide local exhaust at the point where the dust is escaping.This is less desirable than the first because there is potential to expose the operator and you are also losing product so that the business risk is higher.

Another strategy is to provide HEPA filters in the exhaust for the room so that the dust is contained within the room.Airlocks and pressurization are another strategy.Both have the disadvantages of the second strategy above, although the environment and product may still be protected.

Once all the strategies are identified, each one should be looked at for costs, operational impact, etc. to decide which one (s) will be implemented.

A second example might be the risk of exposing the operators to product dust due to dust escaping the tablet deduster. Mitigation strategies might include:

Additional Personal Protective Equipment (PPE) – this may protect the operator, but the PPE might inhibit the operator’s movements and comfort enough so that it is not the best solution.Localized dust collection at the point of generation – this might help with operator exposure, but the product is being wasted which is still a business risk.

Better seals on the deduster to keep the dust inside.Again, this helps protect the operator, but does not reduce the business risk.New dedusting equipment that is more efficient.This solution will be costly, thus increasing the business risk, but again, could reduce risk to the operator.

New formulation to ensure that tablets are less friable and produce less dust in the first place. This is probably the most effective solution, but time, labor constraints, regulatory concerns etc, might preclude implementation.

As you can see, there is rarely a perfect mitigation strategy. The team must look at all aspects, weigh the pros and cons, and determine if the remaining risk is acceptable before making a final decision.This evaluation is repeated for each risk until all the high potential risks have been mitigated. The risk analysis can then be reevaluated with the mitigation strategies in place to ensure that the risks following implementation of the mitigation are all below the defined threshold.

You can see this process of looking at the potential risks, all possible mitigation strategies, and then selecting the most appropriate will take time and effort. This process is not something that can be done in a one-hour meeting, or even in a single setting or day long meeting. Experts in the areas of maintenance, operations, quality, validation, safety, and occupational health will all need to be consulted to define the risks and develop mitigation strategies. Additionally, a champion should be identified to lead the effort in each area in which the risk assessment will take place. This leader should be knowledgeable in the process being evaluated, but also have the skills and training to lead the risk assessment.

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