The dangers of metalworking fluids

Millions of workers worldwide who manufacture parts for automobiles, industrial equipment, aircraft, heavy machinery, and other hardware are exposed to metalworking fluids (MWFs). These fluids, and the additives they contain, are very useful but may cause skin and respiratory problems (harm the nose, throat or lungs). Some studies have also linked MWFs with a variety of cancers, including cancer of the rectum, pancreas, larynx, skin, scrotum, and bladder.

WHAT ARE METALWORKING FLUIDS?MWFs are liquids used in the machining process for cutting, boring or grinding. They are applied to the metal being worked to provide cooling, lubrication and corrosion protection. They contain mineral oils or synthetic lubricants and may be used neat or in a water-mix. They may be called ‘coolant’, ‘suds’, ‘slurry’, ‘soup’, ‘water’ etc. MWFs may also contain other substances such as emulsifiers, stabilisers, corrosion inhibitors, biocides, fragrances and extreme pressure additives.

When do metalworking fluids become harmful?During machining operations MWFs are applied by continuous jet, spray, mist or by hand dispenser. MWFs can harm workers if:

their skin comes into contact with them or
if they inhale them.

During high-speed machine operations, MWFs may form a mist or small droplets and be suspended in the air. These breathable aerosols or oil mist and fumes (smoke) can also affect other people in the workplace not directly involved with the machining process.

HOW DO MWFS AFFECT YOUR HEALTH?Respiratory DiseasesInhaling MWFs mist or aerosol may irritate the nose, throat (pharynx, larynx), and the various conducting airways or tubes of the lungs (trachea, bronchi, bronchioles), and the lung air sacks (alveoli) where the air passes from the lungs into the body. Exposure may also aggravate the effects of an existing lung disease. Some of the symptoms include sore throat, red, watery, itchy eyes, runny nose, nosebleeds, cough, wheezing, increased phlegm production, shortness of breath, and other cold-like symptoms. Some workers have developed asthma. The airways of their lungs become inflamed. Less air flows in and out of the lungs. This results in shortness of breath and a wheezing sound.

Skin Disorders Contact dermatitis is the most commonly reported skin disease associated with MWFs. Workers with contact dermatitis have itchy skin and a rash, often with cracks, redness, blisters, or raised bumps. Straight oils are often associated with acne-like disorders characterised by pimples in areas of contact. Red bumps with yellow pustules may develop on the face, forearms, thighs, legs, and other body parts in contact with oil-soaked clothing.

Two kinds of contact dermatitis are irritant contact dermatitis and allergic contact dermatitis. In irritant contact dermatitis the rash is confined to the area in contact with the irritating substance (MWFs). In allergic contact dermatitis the rash can spread beyond the area directly in contact with the irritant. Once the skin is compromised, very small exposures, which previously did not have any effect, can cause an episode of dermatitis. It is important to try to prevent skin disease from developing and to treat it early because untreated dermatitis can lead to more serious complications.

People working with water-based, synthetic, and semi synthetic MWFs are most at risk of developing contact dermatitis.

Engineering and work practice controls, applied at the source of the hazard, are the most effective means of control.

Box 1

How do you get contact dermatitis in metalworking operations?

How can you prevent it?

from dipping hands into the fluid, handling parts, tools and equipment draining fluids, without wearing gloves/protective equipment
wear protective equipment or wash hands as soon as possible after dipping
touching the fluids while changing and setting tools
wear protective equipment or wash hands as soon as possible after dipping
prolonged contact with the metalworking fluids;
ensure the necessary control measures are in place during these periods
find an alternative job in the workplace if possible
clothing contaminated (soaked) with metalworking fluid resulting in skin contact;
wash clothes thoroughly and regularly and change into new overalls.
metal shavings contained in the fluid may rub/irritate the skin;
drain sump, clean thoroughly and replace with clean fluids.
poor housekeeping practices;
keep work area, machinery and tools that you are working with, clean
higher than recommended metalworking fluid concentrations; high alkalinity of in-use fluid which can remove natural skin oils;
monitor concentrations frequently, dilute as recommended
metal processing aids such as degreasers, cleaners, or rust inhibitors;
monitor concentrations frequently
tramp oils (eg hydraulic fluids, gear or spindle oils, way lubes, grease);
minimise contact as much as possible by using protective clothing
other contaminants (eg water in an oil-based system).
drain and clean and replace with new fluids OR minimise contact as much as possible; use protective clothing
low sump level 30% below the full mark

Check concentration:

if too strong add water to the proper concentration.
If correct fluid was lost due to dragout, add fluid at an appropriate dilution. Monitor all systems carefully, add metalworking fluids on a regular basis, verify correct concentration.
loss of microbial control – Some fluids are treated with microbialcides to kill off any colonisation by microbes. Over time the microbialcides are depleted in the fluid present a good environment for growth.
good work practices on the part of the machinists, including the proper use of controls; proper design and operation of the metalworking fluid delivery system; proper maintenance of equipment; check that additives being used are correct, and that the coolant concentration is correct and not too high.
Sometimes skin irritation can just be from the use of harsh hand soaps or from weather changes.
Use barrier and moisturising creams

Box 2

How do you get contact dermatitis in metalworking operations

How can you prevent it?

Over time MWFs can get contaminated:Normally synthetic fluids are clear, Semi-synthetics are transparent to milky, soluble oil is milky white with no free oil layer

Watch out for these danger signs:- fluid grey or black, yellow or brown; smells bad, a “locker room” smell; dye fading

– floating matter on the fluid

– Tramp oil floating on surface – if the sump is completely covered with oil and the machinist cannot swish the oil out of the way for more than 5 to 8 seconds before the sump is covered again, there is too much tramp oil present. (Major cause of dermatitis!)

– Excessive foam

Bacteria, fungi have contaminated the fluid. Throw away fluid, clean sump properly, replace fluid

Remove as much as possible with a skimmer or pump it off. Check that the filtration system and oil skimmer are working properly.

Skim or pump the surface oil to remove it.

Check fluid concentration, level of fluid, drain and clean

Machinery/tools/parts can also become corroded and rusted or part of the machinery could burn due to excessive heat build-up. All these could lead to contamination of MWFs.

Replace the corroded parts/ burnt part(s) and the MWFs

Preventing respiratory illnesses from MWFsTo reduce damage to workers’ lungs, employers should isolate and ventilate each machine well

Conditions that could lead to respiratory problems are:


* a heavy concentration of machines in a small area; inadequate or poorly designed enclosures and mist collectors; poor general ventilation of the shop and insufficient fresh air; high mist concentrations

* isolate machines and provide proper local extraction ventilation for the machine itself and improve general ventilation on the factory floor.

What is the responsibility of employers?Employers should seek advice from MWF suppliers to ensure that correct fluids are selected for the job and that MWF dispensers are properly maintained and serviced (this includes replacement of old MWFs). Employers must also ensure effective control measures are in place and correct personal protective equipment provided to employees. They should train employees to recognise any signs of MWF exposure and report these to the supervisors or the Company Occupational Medicine Practitioner.

Acknowledgement of Sources

U.S Department of Labor, Occupational Safety and Health Administration (OSHA).
Health and Safety Executive, UK.
National Institute for Occupational Safety and Health (NIOSH).
All photographs, courtesy of Professor Stuart Batterman, Department of Environmental Health Sciences, University of Michigan, USA.

Yogan Gounden, Centre For Occupational And Environmental Health, University of Natal 031-260 4523/4507