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Why coolant mist is harmful to health

Coolant mist: dangers and limits 

Coolant mist (KSS mist) is a mixture of aerosols, vapors, and smoke that is generated during machining. It is respirable, can be carcinogenic depending on its components, and spreads throughout the entire hall. The majority of it is gaseous – and thus invisible. 

How to recognize that your hall is contaminated

Coolant mist is not always visible as a haze. These signs indicate that emissions are entering the hall air:

  • agreasy filmon floors, machines, railings, and lights – including slip hazards,
  • deposits on thehall ceilingand in control cabinets or controls,
  • the typicalmachining odor, which is also noticeable in adjacent areas such as offices or storage,
  • ahaze in the air, especially in backlight or under the hall roof,
  • employees complaining ofirritated airways or eyes.Each of these signs means: condensed vapors and aerosols have left the machine – and are also being inhaled.

What is released into the air during machining

What is released into the air during machining

At high cutting speeds and rotational speeds, cutting fluids cool and lubricate the workpiece and tool and transport the chips away. Due to mechanical and thermal energy, part of it is atomized and evaporated. Cutting fluids are multi-component mixtures of mineral oil or synthetic base substances and numerous additives such as corrosion inhibitors, biocides, or high-pressure additives. Accordingly, the emission mixture is diverse:

  • Mist:liquid aerosols from atomization and condensation.
  • Vapor:gaseous emissions. In Kappa measurement projects, they usually account for 70 to 90% of the total load.
  • Smoke:occurs when cutting fluids burn on hot surfaces – with easily flammable gases and solid particles.

How cutting fluid mist affects humans

The danger arises from the ingredients and the fineness of the emission. Oil mist and oil smoke burden the respiratory tract and can trigger diseases such as bronchitis. Furthermore, cutting fluid mist may contain carcinogenic components: untreated or only lightly refined mineral oils are classified as carcinogenic by the IARC. In water-mixed cutting fluids, carcinogenic nitrosamines such as NDELA can also form, for which there are specific, very low assessment standards in Germany (TRGS 552).

Coolant mist Health risks

The finer, the deeper: Overview of particle sizes

Category

Size

Effect in the body

Inhalable

< 10 µm

enters the respiratory tract

Lung-penetrating

about 2.5 µm

penetrates deep into the lungs

alveolar-accessible

approx. 1 µm

reaches the alveoli

ultrafine

< 0.1 µm

is no longer retained and enters the bloodstream

gaseous (vapor)

–

distributes throughout the bloodstream in the body

Because coolant mist spreads as a diffuse emission throughout the entire hall, employees at adjacent workstations are also affected – not just the person at the machine.

What limits apply

For coolants as a total mixture, there is no health-based workplace limit in Germany. DGUV Regulation 109-003 specifies a technically justified assessment standard according to the state of the art. In Austria, the MAK values for coolants are established in the limit values regulation (GKV). Additionally, the limit values for individual components apply.

Value

Germany (DGUV R 109-003)

Austria (GKV)

Sum of aerosol and vapor

8 mg/m³*

20 mg/m³

of which max. aerosol content

no specific limit

1 mg/m³

How quickly 10 mg/m³ is reached: In a hall with a volume of 2,000 m³ (25 × 10 × 8 m), around 20 grams of dispersed cooling lubricant – roughly the equivalent of a liqueur glass – is sufficient. Added to this is a gap in measurement: many conventional measurements only record the aerosol fraction. As vapour usually accounts for the majority, the actual concentration is thus easily underestimated.

Measure first, then act

Employers must assess exposure as part of the risk assessment. A measurement that captures both vapor and aerosol together is crucial. Kappa Environmental Measurement Technology supports you in this. 

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Interesting facts

FAQ


Yes. Coolant mist is respirable and can damage the respiratory tract, for example in the form of bronchitis. Depending on the ingredients, such as certain mineral oils or nitrosamines, it can be carcinogenic.

In Germany, DGUV Rule 109-003 specifies an assessment limit of 10 mg/m³ for the total concentration of vapour and aerosol. In Austria, the GKV sets a total limit of 20 mg/m³, of which a maximum of 1 mg/m³ may be aerosol.

Oil mist comes from non-water-miscible, mostly mineral oil-based coolants. Emulsion mist arises from water-miscible coolants, which are mixtures of water, oils, and additives.

Vapors usually account for 70 to 90% of coolant emissions, but are not captured by many measurement methods and filters. They enter the bloodstream through the lungs.

Yes, especially with non-water-miscible coolants, flammable and potentially explosive mixtures can form.When planning the facility, a fire and explosion protection assessment must be created. Gemische bilden. Bei der Anlagenplanung ist daher ein Brand- und Explosionsschutzgutachten zu erstellen.

Sources