Exposure

Good management of the metal removal fluid environment includes assessing the level of employees' exposure to MRF. Mist--the droplets of MRF that escape into the air--should be controlled to within the guidelines described below.. Exposure of the skin to MRF should also be kept to a minimum. One of the goals of MRF management is to keep the workplace safe and comfortable for workers, and keeping track of the level of exposure is important in order to achieve that goal. Here is where you can learn about assessing and reducing workers' exposure to in-use MRF and its contaminants.

qualitative assessment

quantitative assessment

exposure
monitoring

notification to employees

when symptoms appear

exposure-reduction plan

     description
     timetable
     controls

personal filter sampling

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More on exposure

How does the employer assess workers’ exposure to MRF and fluid contaminants?

There are two kinds of assessment: qualitative and quantitative.

A qualitative assessment identifies shop areas where exposure to MRF is possible and makes an estimate of mist or dermal exposure hazards. Such estimates are made based on experience, possibly with the aid of a direct-reading aerosol instrument. For example, in some MRF operations, such as automated transfer lines performing a variety of machining operations, operators do not routinely come into contact with the MRF. In contrast, maintenance employees on such transfer lines may be required to change or adjust tools and be exposed to MRF for extended periods. Qualitative assessment is particularly important with regard to dermal (skin) exposure. The assessment of dermal exposure should be factored into the overall assessment of exposure

Quantitative assessment measures the amount of exposure to MRF. These methods are normally used only for air contaminants. Area or personal samples are taken in the workplace and analyzed to determine the average concentration of the contaminant. The most common contaminant measured in machining operations is the MRF aerosol (particles in air). In some instances, direct-reading aerosol monitors may be used to study changes in in concentration over time or to estimate the average aerosol concentration.

When is exposure monitoring needed?

Exposure monitoring is generally performed in response to employee concerns, complaints, symptoms of irritation or health effects, or where experience indicates that exposure to MRF aerosol may be relatively high. Exposure monitoring is not needed if the employer can show that employees have not reported signs or symptoms of respiratory conditions associated with metal removal fluid exposure.

If there is a significant change in production, equipment, process, product formulation, or control measures that might cause new or additional exposure to metal removal fluids, employee exposures should be re-evaluated.

Must employees be notified of the results of monitoring MRF exposures?

Employers must notify the affected employee(s) of the results of the monitoring of metal removal fluid exposure. Notification should be in writing, either by distributing copies of the results to the employees or by posting the results.

What if employees have reported respiratory or dermal symptoms associated with MRF exposure?

In this case, the employer should develop and carry out a plan to reduce employee exposure or otherwise address management of the metal removal fluids affecting the employee(s). If the employer already has such a plan in place, it needs to be re-evaluated and modified as needed.

What should be included in a plan to reduce employee exposure?

a description of how the exposure is to be reduced or how the fluid management issue is to be otherwise addressed

a timetable for putting the plan into practice

if necessary, institution of engineering and work practice controls to reduce exposures and keep them below the exposure guideline before requiring the use of respiratory protection or other personal equipment

ASTM Standard Practice E 1972-98 sets forth guidelines for minimizing effects of aerosols in the MRF environment.

The employer should communicate the plan through employee information and training.

What method should be used for quantitative personal filter sampling of MRF aerosol?

Historically, airborne metal removal fluid in the workplace were sampled using various filter media and air pumps to collect the airborne particulate. The collected samples were then subjected to a variety of analytical techniques to provide estimates of the exposure level.

The composition of MRFs varies greatly, as do the analytical techniques. Therefore, it has been very difficult to compare different operations using different MRF and even different workstations within a given plant. Applying historical air sampling data to industry-wide exposure studies can be problematical and can lead to large errors unless the differences in analytical techniques are accounted for.

If your job requires you to sample for MRF, or if you simply want to know the technical details, go to personal sampling.

What is an acceptable limit for aerosol exposure to MRF?

Whenever an analytical measurement is made, there is a desire to compare the result to a standard. After all, comparing a dimension of a part to its specification tells us if the part has been made correctly. However, the aerosol measured in the metal removal fluid environment is a highly complex mixture of materials.

The workplace contaminants that cause respiratory irritation and other possible health effects are unknown at this time. Since we don't know what to look for, simply comparing the overall aerosol concentration measurements to a standard value will not ensure the health and safety of employees in the shop. Only by a comprehensive systems approach will the environment be managed safely and cost-effectively.

Even though we don't know what in the complex and variable MRF aerosol is responsible for the respiratory complaints, we do know that, in general, lower concentrations are less likely to produce adverse reactions. Employees often experience irritation when 8-hour Time Weighted Average (TWA) exposures exceed 2 mg/m³ , but irritation is much less likely to occur when the exposures are less than 1.0 mg/m³.

We believe that good management of the MRF environment should include actions to control MRF aerosol concentrations in the shop. However, since the relationship between exposure and adverse health effects is not well understood, a specific exposure limit cannot be established to ensure the health of the workforce. For this reason, we favor an Occupational Exposure Guideline (OEG) for all fluid types and formulations that would be part of a comprehensive systems approach to MRF management. We believe that an 8-hour TWA of 1.0 mg/m³ extractable MRF, as measured by ASTM PS 42-97, is achievable over time and that it represents a reasonable target given the variability of the MRF environment and the lack of definitive health and toxicology information.

What are the management components of the OEG?

If any exposures in your shop are above 2 mg/m³, an exposure reduction plan should be prepared to promptly reduce all exposures to below 2 mg/m³.

If exposures in your shop are between 1 and 2 mg/m³, an exposure reduction plan should be prepared to reduce exposures to less than 1 mg/m³ as soon as practicable, but not later than 2005 (5-year implementation).

If exposures in your shop are consistently below 1.0 mg/m3, the exposure reduction plan should focus on long-term improvements. Any building modifications or procurement of new or replacement equipment should include mist control considerations to minimize workplace aerosol concentrations.

Regardless of exposure concentrations, if complaint investigations indicate that MRF aerosol exposures are causing signs or symptoms of respiratory problems, an evaluation should be preformed to determine if further exposure reduction is necessary or feasible.

See More on Exposure for a discussion of aerosol exposure levels.