The Essential Role of Mist Collectors in Industrial Settings

August 2nd, 2024 | Posted in Air Cleaners

NIOSH recommends using mist collectors engineered for the operation and specific machine enclosures. WHY?

A question our air quality technicians get asked is: “What is so bad about coolant mist that we should install mist collection equipment?”

A perfectly rational question, it led to spending a little time Googling Safety Data Sheets for Metal Working Fluids. Although in the shop we use the term “coolant,” in the scientific literature, the term most frequently used for coolant and coolant mist is “metal working fluid” or “MWF.” If you go to Google Scholar to do your own research, the term “metal working fluid” is likely to bring up more relevant references than “coolant mist.” Broadly speaking, metal working fluids are often grouped as either water soluble or straight oil coolants. What are the health hazards?

Coolant Mist Health Hazards

Synthetic and Semi-synthetic (water soluble) coolant representative health hazards are summarized below:

[1] According to the Encyclopedia Britannica tall oil is a by-product of the sulfate (kraft) process of paper manufacture. It is principally a mixture of resin acids, such as abietic acid, and fatty acids, obtained by chemically treating the cooking liquor used in the operation of pulping wood for paper.

Straight oil coolant representative health hazards are summarized below:

Please note that the above summaries are not to be considered all-encompassing. We recommend that you review the Safety Data Sheets (SDSs) for the coolants used at your facility to identify their specific health hazards.

Other potential adverse health effects include.

• Folliculitis (inflammation of hair roots or follicles). Caused by prolonged and regular contact with straight oils.
• Oil acne (red bumps with yellow pustules/ blisters filled with pus). Caused by skin contact with oil-soaked clothing. Can develop on various body parts: face, forearms, thighs, legs, etc.

Possible Increased Cancer Risk – Straight Oils

According to the Canadian Centre for Occupational Health and Safety (CCOHS)^[i]:

“In addition, while the extent of the problem is not clear, there is the potential for straight oils to be heated during use (usually at the site where the cutting tool works on the metal workpiece), and the temperature may increase high enough to cause the formation of polynuclear hydrocarbons (or polyaromatic hydrocarbons, PAHs).”

The Agency for Toxic Substances and Disease Registry (ATSDR) notes that some PAHs are associated with increased incidences of skin, lung, bladder and stomach cancers^[ii].

Possible Increased Cancer Risk – Water Solubles

Some biocides used to control microbial growth in water soluble coolants release formaldehyde. The CCOHS notes that:

• Nitrites or nitrates and amines that cause the formation of nitrosamines when MWFs are heated or under pressure. Certain nitrosamines, such as N-nitrosodiethanolamines (NDELA), are known to be cancer causing agents.
• Some biocides release formaldehyde, a suspected carcinogen. Formaldehyde can also speed up the formation of nitrosamines.
• Chlorinated paraffins are carcinogens (often used when extreme pressure is required). They also form dioxin, another carcinogen.

Dermatitis

In addition, work conducted by Geier (2020) has associated coolant mist exposures with allergic contact dermatitis in metalworkers^[iii]. “Occupational irritant contact dermatitis is an inflammation caused by substances found in the workplace that come in direct contact with the skin. Signs of irritant contact dermatitis include redness of the skin, blisters, scales or crusts.^[iv]” “Allergic contact dermatitis” is a different malady. This response to coolant mist exposure is a form of dermatitis/eczema caused by an allergic reaction to a material, called an allergen, in contact with the skin. The allergen is harmless to people that are not allergic to it^[v]. Therefore, not every worker in the shop will be equally affected by exposure to MWF mist.

Furthermore, the peer-reviewed scientific literature contains a number of reports describing contact dermatitis from the coolant mist the shop air, as well as from having the coolant liquid in direct contact with the skin from handling machined parts.

In his 2020 paper, Geier notes that the most important allergens in Synthetic and Semi-synthetic MWF are monoethanolamine (MEA) and oxidation products of resin acids. Resin acids are contained in distilled tall oil, which is a widely used basic MWF component. According to Geier (2020) other frequent sensitizers in MWF are:

• formaldehyde,
• formaldehyde releasers,
• and other biocides such as isothiazolinones.

Dilute MEA exposures are also associated with eye and skin irritation^[vi]. Formaldehyde health effects include skin and eye damage as well as possible increased cancer risk^[vii].

Microbes and Biocides

Hydrocarbons are a common component of metal working fluids. Therefore, the coolant reservoirs of our machine tools contain warm water and hydrocarbons – an environment that encourages microbial growth. Gilbert et. al. (2020) conducted a study of hypersensitivity pneumonitis of machinists exposed to metalworking fluids. They found that the pneumonitis was linked to Mycobacterium immunogenum. In addition to Mycobacterium, impacts of continuous and massive contact to other micro‐organisms, such as Pseudomonas, were studied. They concluded that “Very high concentrations of bacteria were found in most MWF studied and limited biodiversities were observed. Many species of micro‐organisms were retrieved from MWF samples, but they were mostly colonized by Pseudomonas pseudoalcaligenes and Ochrobactrum anthropic.^[viii]

In order to control microbial growth, it is common practice to use biocides in the coolant. When using biocides to control microbial growth, it must be borne in mind that the components of many biocides, for example formaldehyde, have adverse health effects as noted above. Sensitizers and irritants found in biocides may include the following:

• Boric acid
• Triethanolamine
• Diethanolamine
• Monoethaolamine
• Triazine biocide (often listed as “proprietary” Triazine combines with water to release formaldehyde)

Controls

NIOSH recommends the following “Proper application procedures:^[ix]”

• applying MWFs at the tool/work piece interface to minimize contact with other rotating equipment;
• ceasing fluid delivery when not performing machining;
• not allowing MWFs to flow over the unprotected hands of workers loading or unloading parts; and,
• NIOSH recommends using mist collectors engineered for the operation and specific machine enclosures.

Air Quality Engineering offers a wide range of air cleaners designed specifically for mist collection applications. Single and multiple pass electrostatic air cleaners are available in a range of sizes and configurations as well as media filtration units where that application is appropriate. Contact Air Quality Engineering for information on mist collection.

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[i] https://www.ccohs.ca/oshanswers/chemicals/metalworking_fluids.html

[ii] https://wwwn.cdc.gov/TSP/ToxProfiles/ToxProfiles.aspx?id=122&tid=25

[iii] Geier, J., Lessmann, H. (2020). Contact Allergy to Metalworking Fluids. In: Johansen, J., Mahler, V., Lepoittevin, JP., Frosch, P. (eds) Contact Dermatitis. Springer, Cham. https://doi.org/10.1007/978-3-319-72451-5_36-2

[iv] https://www.ccohs.ca/oshanswers/diseases/dermatitis.html

[v] https://dermnetnz.org/topics/allergic-contact-dermatitis

[vi] https://www.alliancechemicals.com/wp-content/uploads/2019/01/MEA-sds.pdf

[vii] https://www.fishersci.com/store/msds?partNumber=F75P20&productDescription=FORMALDEHYDE+37%25+20L&vendorId=VN00033897&countryCode=US&language=en

[viii] Y. Gilbert, M. Veillette, C. Duchaine. Metalworking fluids biodiversity characterization. Journal of Applied Microbiology, Volume 108, Issue 2, 1 February 2010, Pages 437–449, https://doi.org/10.1111/j.1365-2672.2009.04433.x

[ix] “What you need to know about Occupational Exposure to Metalworking Fluids U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES, Public Health Service
Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health. March 1998. DHHS (NIOSH) Publication No. 98-116