What Are the Health Risks of Bacteria-Contaminated Metalworking Fluid?
Metalworking fluid serves to lubricate, cool, suppress, protect, and carry away chips from the zone of action. However, water-miscible fluids often contain the nutrients necessary for bacterial growth. Poor concentration, pH, filtration, circulation, or housekeeping practices can encourage the proliferation of bacteria in the fluid. Contaminated coolant is a significant concern and not only gives off an unpleasant odor but can also present direct contact, splash, contaminated surface, and mist exposure hazards.
Adverse health effects such as dermatitis, skin absorption, eye irritation, and lung infection can occur from the exposure.
Why Does Bacteria Grow in Metalworking Fluid?
Water-miscible coolant constantly accumulates certain materials from the machining process. These include tramp oil, metal fines, dirt, organic matter, and substandard makeup water. The above-mentioned materials may combine with the contents of the sumps and piping to encourage the development and proliferation of microorganisms.
Standing pockets and chip beds provide an excellent breeding ground for massive populations of microbes. Tramp oil in the fluid can be a source of nutrients and reduce the oxygen content at the fluid’s surface, encouraging the growth of certain bacteria. Once the contamination has infested the sump and circulation system, the treatment of the fluid may not penetrate the film and debris, which harbors the microflora.
Skin Exposure and Dermatitis
Direct contact with contaminated fluid occurs when a worker comes into contact with wet parts, reaches into a machine, cleans a machine, or wears contaminated clothes. Dermatitis develops as a result of working with metalworking fluid. The following are the symptoms of dermatitis: redness and itchiness, croaky and rough skin, and acne or blisters.
It is not always easy to distinguish irritant contact dermatitis from allergic contact dermatitis because both conditions have similar symptoms. The damaged skin can be re-irritated even by minor exposure to the coolant. The above symptoms are caused mainly by the coolant concentration, alkalinity, additives, tramp oil, metal fines, and bacteria, and one should not assume that bacterial infestation is the only cause of dermatitis.
Can Contaminated Coolant Mist Harm the Lungs?
The machining process generates mist and/or aerosol from the metalworking fluid. In this regard, it is not surprising that bacteria or toxins accompany the fluid, which a worker breathes in during the machining process. Some of the symptoms observed in the lungs and airways are coughing, wheezing, sore throat, runny nose, more phlegm, chest tightness, and shortness of breath. Exposures to airborne agents can irritate the airways, leading to exacerbation of an existing lung disease or triggering new diseases such as occupational asthma and chronic bronchitis.
Hypersensitivity pneumonitis (HP) is a severe but rare lung disease triggered by repeated inhalation of certain microorganisms from contaminated water-miscible working fluid. HP presents with flu-like symptoms such as coughing, fever, chills, muscle cramps, tiredness, and shortness of breath. Late-stage HP brings about permanent lung damage. It is critical that workers obtain proper medical attention if they experience any of these symptoms after exposure.
“Bacteria-contaminated metalworking fluid is not just a coolant-quality problem. Once microbial growth becomes established, workers may be exposed through skin contact and airborne mist. Consistent monitoring, proper system cleaning, and proactive microbial control are far more effective than waiting for odor or employee symptoms to reveal a problem.”–Jason Gardiner, CEO
Odor Is a Warning, Not a Complete Test
A rancid or locker-room odor usually warns of uncontrolled microbes, but other factors may contribute to offensive odors. The fluid in the sump may have become out of control long before the strong odor develops, and the strong odor may emanate from masking agents in the product. Other indications that the fluid may be out of control include gray or black fluid, floating growth, abnormal foaming, pH shifts, plugged fluid lines, corrosion, poor fluid breakup, and employee complaints. Odor should not be the sole criterion in determining whether or not the fluid is in control.
The change in appearance should be a reason for closer scrutiny of the fluid or the process. A simple corrective treatment may not suffice if the system is heavily contaminated. Corrective treatments should be guided by the supplier’s recommendation. If a small amount of microbes infests the fluid, it may be controlled by a properly selected and applied treatment. However, if the contamination is severe, it might require a complete sump cleaning and recharging before the fluid can be used again. Treatments should always be compatible with the coolant and should be applied as recommended by the manufacturer since excessive biocides may be an irritant to the eyes and skin and cause sensitization.
A Safer Fluid Management Program
Better microbial control starts with keeping the recommended concentration and pH within the manufacturer’s range and eliminating tramp oil, debris, and other sources of microbial nutrition. Efforts should also be made to keep the sump free of standing pockets of fluid, to minimize stagnant zones, and to maintain the coolant system to prevent blockages in the pipes. Thorough documentation of test results should also be made, noting any changes in the fluid and identifying areas where corrective measures can be taken. Enclosures and local exhaust ventilation can also help by reducing the formation of mist at the source. Workers should also wear appropriate safety equipment, wash hands with gentle soap, avoid wearing harsh industrial clothes, and be trained not to use harsh solvents or other industrial cleaners.
OSHA recommends routinely testing water-miscible metalworking fluids for microbial content, concentration, pH, tramp oil, and suspended solids and taking corrective measures when the test results show values outside acceptable ranges.
When Should Employee Symptoms Be Investigated?
New rash, recurrent eye or throat irritation, persistent cough, wheezing or chest tightness, fever and chills, and shortness of breath are not ordinary workshop ailments. Employees should present any of these symptoms to the occupational health care facility for testing and treatment. A physician should evaluate unexplained symptoms, and if the symptoms disappear on their own when away from the workplace, they should return to work and report them again while away from the machining area.
Management should take notice of recurring employee symptoms and evaluate possible exposure to a harmful biological agent. A pattern of similar symptoms among multiple workers or clustering of symptoms around particular machines, shifts, or coolant systems may indicate a need to investigate potential exposure further.
Protecting Workers and Coolant Performance
Good bacterial control protects the sump as well as the operators’ safety, health, and productivity. The most effective way of achieving safe and efficient metalworking fluid is through monitoring, contamination control, proper mist control and system cleaning practices, and an appropriate program to control the microbial content of the fluid based on the type of coolant and the system. Contact the professionals at Big Sky Decon if you’re interested in learning more about the health risks of bacteria-contaminated metalworking fluid and how to avoid these encounters.
What Do Buyers Ask About Metalworking-Fluid Control?
Q: Does foul-smelling coolant always contain harmful bacteria?
A: A foul odor often accompanies uncontrolled microbial content. However, it does not necessarily mean that the fluid contains harmful bacteria. It only means that the fluid contains high organic material, which supports the bacteria’s growth. Further tests should be conducted to determine the level of contamination, pH, concentration, tramp oil, and solids. The shop should evaluate the fluid’s filtration and circulation systems.
Q: Can contaminated metalworking fluid be treated without replacing it?
A: Depending on the level of contamination, the shop can treat the fluid without replacing it. In the event of early or minor infestation, an appropriate corrective treatment, together with a change of conditions that promote bacterial growth, may help. Sometimes, a thorough cleaning and recharging of the sump are necessary to remove biofilms, which harbor the bacteria, from the sump and the machine. It is, therefore, essential to analyze the fluid to determine the level of contamination to guide the next steps of either treating or replacing the fluid.
Q: How often should a shop test its coolant for bacteria?
A: The frequency with which the shop should test the coolant depends on several factors, such as the type of fluid, the size of the sump, and the production rate. Usually, the shop should consider the manufacturer’s recommendation. The recommended testing schedule enables the shop to evaluate the trend in test results to make better decisions regarding the fluid. The shop should also test the fluid more when the test results change significantly or when a worker reports symptoms that may result from exposure to contaminated coolant.
Q: Is adding more biocide the best way to solve bacterial contamination?
A: No, adding more biocide is not the best way to solve the problem. The biocide should be compatible with the fluid. The manufacturer should, therefore, be consulted to recommend the best biocide that is suitable for the fluid, type of bacteria, level of contamination, operating conditions, and any other relevant factors. The excessive use of biocide can cause adverse effects to the skin and eyes and may cause irritation. Other measures that the shop can use to control microbial growth include removing tramp oil and other materials that promote the growth of bacteria, ensuring that the system is free from blockages, and minimizing exposure to biologically active agents.