Respiratory Effects

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prevention

MRF choice

proper fluid maintenance & testing

proper fluid application

maintain MRF systems

cover & ventilate flumes

maintain enclosures

maintain mist collectors

machine tool feeds and speeds

minimize flow rates

reduce fluid pressure

avoid blowoffs

outside air

no smoking

The respiratory effects of inhaling MRF mist are not entirely understood. Exposure to MRF mist can cause irritation of the eyes, nose, and upper airways in some people. Recent studies have also shown that groups working in MRF environments have higher rates of respiratory symptoms such as cough, wheezing, and shortness of breath, than comparison groups. Not all individuals exposed to MRF develop such respiratory symptoms.

Recent studies have shown that undesirable respiratory effects can occur when MRF mist reaches certain levels. Yet these studies do not always agree on the relationship of MRF and respiratory symptoms. NIOSH (the National Institute for Occupational Safety and Health) has recently published a criteria document that brings together and reviews the results of such studies, Criteria for a Recommended Standard: Occupational Exposure to Metalworking Fluids

Other factors, such as smoking, increase the possibility of respiratory disease. In light of the concern over potential adverse respiratory effects in the metal removal fluid environment, tobacco use in the presence of metal removal fluids should not be permitted as a general practice.

What is respiratory irritation and how is it related to MRF exposure?

In general, respiratory irritation involves some type of chemical interaction between the MRF and the cells that are part of the human respiratory system. These cells can be part of one or more of the following areas: nose, throat (pharynx, larynx), the various conducting airways or tubes (trachea, bronchi, bronchioles), and the lung cells (alveoli).

Respiratory irritation has been associated with exposure to MRF mist in some instances. Some of the symptoms reported include sore throat, runny nose, nose-bleeds, cough, wheezing, increased phlegm production, and other cold-like symptoms. When symptoms of respiratory irritation do occur, it is unclear whether the irritation results from specific fluid components, contamination of the in-use fluid, or a combination of factors. Concern has been raised that daily or recurrent episodes of symptoms associated with respiratory irritation may be an early warning for the possible onset of occupational asthma. Controlling exposures and employing good fluid management is essential to minimizing and preventing the symptoms of respiratory irritation.

What is asthma and how is it related to MRF exposure?

Asthma is a common respiratory disease in the general population. Some studies show that asthma may be associated with exposure to MRF. Asthma is an allergic disease of the large airways in the lung. During an asthmatic attack the airways are narrowed, and it is more difficult to get air in and out of the lung. It is unclear whether exposure to in-use MRF causes asthmatic reactions or the development of asthma in workers without a history of asthma.

What is chronic bronchitis and how is it related to MRF exposure?

Chronic bronchitis is a clinical disorder involving the mucus-secreting cells of the large airways. Chronic bronchitis is characterized by chronic productive cough and inflammation. The inflammation is, by definition, chronic. With inflammation comes an excessive production of mucus. The mucus can interfere with air passage into and out of the lungs. As in asthma, particular MRF ingredients or contaminants may cause this condition.

What is hypersensitivity pneumonitis?

Hypersensitivity pneumonitis is a rare allergic inflammatory disease of the deep lung. At first symptoms are like those of the flu; however, in some cases it can lead to serious long-term effects. Several clusters of the disease have been documented since 1991. Only a small minority of exposed workers appears to be susceptible. There is currently no identified cause of the disease; however, maintaining the MRF environment as recommended in this document may help to prevent this disease.

What in the MRF is responsible for respiratory effects?

There are no identified causes of respiratory effects in the MRF environment. Most investigations have focused on irritant chemicals, microbiological contaminants of water-based fluids, and airborne particles as likely causes. At this time there are no clear answers.

How can respiratory effects be prevented?

Without identified causes of respiratory effects, we must focus on general principles of good manufacturing practices. The following practices will reduce or prevent respiratory effects of in-use MRF by improving fluid management or reducing aerosol generation:

Select an appropriate MRF for the operation that does not contain highly irritating components.

Select fluids that will minimize aerosol generation

Maintain the fluid properly by monitoring concentration, removing contaminants and controlling microbial growth in water-based fluids. Excessive concentration of tramp oil can increase aerosol generation.

Minimize mist generation by proper fluid application.

Maintain MRF delivery systems, including pumps and seals, to minimize aerosol generation. Introduction of air into the fluid through leaking pump seals or inlet lines will increase mist generation.

Cover flumes on central systems and ventilate if possible

Maintain existing machine enclosures and guarding to minimize release of MRF aerosols; restore/replace missing enclosures.

Enclose and ventilate the machines if necessary to keep mist levels at an acceptable level.

Properly maintain mist collectors and exhaust ductwork leading from machine enclosures.

Optimize machine tool feeds and speeds to achieve the desired machining performance while minimizing aerosol generation.

Minimize fluid flow rates, consistent with the desired machine performance.

Interrupt fluid flow when not needed for the metal removal operation.

Reduce fluid pressure consistent with machine performance.

Avoid use of compressed air probes or "blowoffs."

Provide adequate outside air through the general ventilation system.

Discourage smoking in the MRF environment. Employers should assist workers who want to stop smoking.

Employees with symptoms of respiratory irritation or other effects should seek medical treatment.