Understanding Metalworking Fluids: Types, Risks, and Control Measures
Learn about the four categories of metalworking fluids, including their risks and control measures.
What are Metalworking Fluids?
Metalworking fluids (MWFs) refer to fluids used during grinding and machining and include four classes of MWFs: straight oil, soluble oil, semisynthetic, and synthetic MWFs. MWFs serve to prolong the life of the tool, carry away metal debris that results from cutting and grinding, protect the part being produced, and carry heat away from the ground or cut surface.
Occupational exposures to MWFs are a concern and need to be controlled. Repeated inhalation of MWF mists can cause respiratory illnesses and asthma, leading to non-reversible lung damage. Additionally, contact with skin can cause various skin diseases, most notably allergic dermatitis.
Types of MWFs
MWFs are grouped into four categories. The first category is “straight” oil (neat oil) MWFs. These oils are solvent-refined petroleum oils, animal, marine, vegetable oils, or synthetic oils that are not diluted with water. The straight oils may or may not contain additives that may include corrosion inhibitors, emulsifiers, buffers, and extreme pressure additives.
The next class are the soluble oils (emulsifiable oils), which are between 30 to 85 percent severely refined lubricant base oil with emulsifiers and may also contain additives. Soluble oils also contain a small percentage of water.
The semisynthetic class contains less of a percentage of the severely refined lubricant base oil (5-30%) and contains a higher percentage of emulsifiers and up to 50 percent water.
The final category is synthetic MWFs, which contain no petroleum oils and are diluted with 10-40 parts of water.
Occupational Exposure
Occupational exposures to MWFs occur either by inhaling mists and aerosols or from direct skin contact. Besides the MWF aerosols and the added additives or biocides, exposure risk can include metals and alloys from the parts ground or machined. Additionally, background contaminants in the work area and bacterial or fungal contamination in the water component of MWFs pose a risk.
The National Institute of Occupational Safety and Health (NIOSH) has established a Recommended Exposure Limit (REL) of 0.5 milligrams per cubic meter (mg/m3) for an eight-hour time-weighted average exposure. The REL applies to all categories of MWF. In addition to NIOSH, the Occupational Safety and Health Administration has established a Permissible Exposure Limit (PEL) of 5 mg/m3, which only applies to mineral oil-based MWFs. The NIOSH REL is based on regular and recent reviews of health hazard data and is the occupational exposure limit referred to for best practices.
During machining operations, the risk of Inhalation exposures is greater depending upon how close the worker is to the machine, whether there is an enclosure or splash guard, and whether the machine is operating at a high speed and making deep cuts. Other factors contributing to exposures during machining or grinding are whether there is exhaust ventilation installed to capture mists and aerosols near the point of generation and whether the exhaust system has been poorly designed or maintained. Additionally, improper machine maintenance can result in excessive fluid application or contamination of the oil with machine tramp oils.
In addition to inhalation, skin contact is a major concern with respect to exposure. Exposures occur when there are not enclosures or guards to protect from splashes during machine operation, and from handling parts, tools, or equipment without personal protective equipment (gloves and aprons), or prolonged contact with clothing contaminated with oil.
Health Effects
The NIOSH REL was established to address non-malignant respiratory disease. MWF concentrations above the REL in nine out of ten studies have been shown to cause respiratory conditions, including hypersensitivity pneumonitis (HP) which produces flu-like symptoms, acute airway irritation, chronic bronchitis, impaired lung function, and asthma. Cases of HP have been linked to water-based or diluted oils, and microbial contamination is believed to be the most likely cause. Three recent studies have shown that the risk of developing asthma is elevated and up to three times greater for workers exposed to synthetic MWFs than for workers who are not exposed.
A variety of skin diseases can result from direct skin contact with MWFs. The following factors contribute to the development of disease:
The MWF category and additives used
The duration of the skin contact
An existing skin abrasion or cut
Individual susceptibility
Inadequate or infrequent skin cleansing following contact
The use of irritating soaps or detergents
High or low humidity, hot or cold temperatures
Wearing MWF-soaked clothing or handling soaked rags.
The general cleanliness of the surrounding work area
Lack of controls i.e., machine enclosures, exhaust ventilation, personal protective equipment (gloves, sleeves, aprons)
The most reported skin diseases are irritant contact dermatitis or allergic contact dermatitis. The latter type of dermatitis is caused by an immune response to a substance that the body has become sensitized to. Dermatitis causes skin lesions and discomfort from burning and itching. Dermatitis is common with contact with soluble, semisynthetic, and synthetic MWFs.
Other skin diseases, including folliculitis (hair follicle infection), oil acne, and keratosis (rough, scaly skin patches), are linked to contact with straight oil MWFs.
Controlling Exposures to MWFs
The machine tool industry has undergone major changes in recent decades, leading to significant exposure reductions. The changes made have included the increased use of synthetic MWFs, which have increased tool and cut speeds which reduce machining time. Technological advances have also been made, leading to the development of machines with partial enclosures and the installation of local exhaust ventilation. During the 1970s and 80s, industries began installing air cleaners (mist collectors) and improving the recirculation of air and filtration.
Recommendations for Controlling Exposures
NIOSH recommends developing and implementing a comprehensive health and safety program to control exposures to MWFs. For programs to succeed, management must have a strong commitment and include worker involvement. The four main components recommended are safety and health training, worksite analysis, hazard prevention and control, and medical monitoring of exposed workers.
Worker training programs should teach workers to identify potential exposure hazards in their work areas and the adverse health effects of MWF exposure.
Worksite analysis refers to monitoring work practices and assessing personal exposures (air sampling) to assess the effectiveness of controls.
Hazard reduction can be achieved by the proper selection of MWF, i.e., using the most non-irritating, non-sensitizing fluids, regular fluid maintenance, isolation of the operation, and installation of exhaust ventilation.
With respect to PPE, workers should be trained in the proper use and care of protective equipment. If personal exposure assessment indicates that respiratory protection is needed, a respiratory protection program must be established in accordance with the OSHA Respiratory Protection standard (29 CFR 1910.134).
For more in-depth information about MWFs and controlling exposures, consult NIOSH publication 98-116, Occupational Exposure to Metalworking Fluids
Mary Dunlap is a Certified Industrial Hygienist and has been with Cornerstone Environmental, Health and Safety since 2016. When she is not working, you can find Mary enjoying the outdoors.
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Controlling Occupational Exposures
The role of an industrial hygienist is to recognize potential exposure hazards, evaluate exposures, provide input for the development of controls, and finally evaluate control methods for effectiveness in reducing exposures.
When controls are warranted, the process begins with a risk assessment to characterize the problem. The hygienist can provide assistance in identifying and characterizing the hazard, the emissions and sources, worker involvement with the sources and how air movement occurs.
Control measures can be grouped into three categories: administrative, engineered, and personal protective equipment. When considering controls, there are five fundamental assumptions to bear in mind:
All hazards can be controlled (to some degree).
There are different approaches for control.
Sometimes, more than one control method is needed.
Some control methods are more cost-effective than others.
Controls may not always be completely effective in limiting the exposure hazard.
Administrative controls place part of the burden of control on the worker and are often not completely effective when used as a single approach. Examples of administrative controls include rotating workers, providing best practice training for performing job tasks, improving personal hygiene, and implementing housekeeping programs.
When considering options, it is necessary to evaluate the sources of exposure, the way in which it can affect the worker, and the route of entry. Typical routes may include unprotected exposure to noise, skin contact or inhalation of vapors and aerosols. The controls considered should be matched with the employee, the process or task, and be cost-effective. In some cases, there are regulatory requirements for controls such as the OSHA (Occupational Safety and Health Administration) requirement for exhaust ventilation for abrasive blasting (1910.94).
Worker rotation is frequently used to reduce the amount of time a worker is exposed to a hazard. A common example is rotating workers performing jobs in high-noise areas. Another example is to move workers every few hours who perform highly repetitive job tasks to reduce musculoskeletal strain.
Training in good work practices can significantly reduce exposures. For example, coaching proper body postures such as how to stand and position the head while welding or reinforcing the need to face forward to work and pivot feet instead of twisting the body.
Good housekeeping and personal hygiene are also important components of administratively controlling exposures. Settled dust becomes a secondary source of exposure with increased air movement, traffic activity and vibration produced by equipment. Frequent cleaning helps to prevent dust accumulating on surfaces.
Training and reinforcing the need for personal hygiene, such as frequently washing hands and avoiding hand to mouth contact while working can reduce the risk of exposure by ingestion. Several standards contained in OSHA 1910 Subpart Z for toxic and hazardous substances mandate personal hygiene practices. Administrative controls are usually used in conjunction with engineered controls.
Although they are more expensive to implement, engineered controls are the most effective since they offer greater cost savings over time. Examples of engineered controls include source modification, substitution, process change, isolation, and ventilation. The development and installation of engineering controls is usually the responsibility of a facilities engineering department and maintenance staff.
Source modification refers to changing an emission source to make it less hazardous. An example of source modification is wetting dust particles released in a foundry shakeout operation to reduce dispersion. Another example may be to reduce temperatures to lower the level of chemical off-gassing and vaporization.
Modifying a process to reduce the hazard is another type of engineered control. An example of this would be to dip rather than to spray paint parts. Automation would also be an example of changing the process. A good example is robotic welding to replace manual welding.
Substitution refers to changing to a different material, type of equipment, or process to reduce the hazard. Examples include substituting a solvent having a low occupational exposure limit (OEL) and higher vapor pressure to a different solvent having no established OEL, or a lower OEL and less volatility.
Isolation refers to separating employees from hazardous processes, equipment, or environments. Isolation can be achieved by placing barriers around equipment or materials, such as the use of ventilated flammable cabinets or placing enclosures around high-noise sources. Isolation separates employees from hazards. Examples are control rooms, isolation booths and supplied air islands.
Ventilation is frequently used as a method to control emissions near the source or to dilute emissions to levels that are acceptable. Local exhaust ventilation (LEV) attempts to eliminate emissions to the work room air. LEV controls are designed to capture, control, or eliminate emissions using control structures such as hoods, exhausted enclosures, ductwork, air cleaners, fans, and exhaust stacks.
General exhaust ventilation relies on fresh air dilution, either by open doors, windows or make-up air provided by air intakes and ventilation systems. For constant emission sources, effective dilution relies on good air mixing and constant air flow.
In addition to engineered solutions, regular and preventative maintenance is an important part of preventing uncontrolled and unexpected exposures. Insufficient maintenance could result in a catastrophic failure such as a rupture failure, increasing leaks from flanges, seals, access doors, and breakdowns of equipment.
Personal protective equipment (PPE) should always be used as the last option for control when other methods of control are not feasible or effective enough to reduce exposure to safe levels. Relying solely on earplugs or respirators places the burden of control on the worker and the protection is only as good as how properly the PPE is fit, worn, and maintained.
There are many different options to help keep workers safety, contact us to evaluate exposure concerns in your facility.
Mary Dunlap is a Certified Industrial Hygienist and has been with Cornerstone Environmental, Health and Safety since 2016. When she is not working, you can find Mary enjoying the outdoors.
Source: Case Studies: Sixty Practical Approaches of OH&S Control Principals. D. Jeff Burton, MS, PE (former CIH (Certified Industrial Hygienist), CSP)
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Industrial Hygiene Services Prevent Health Hazards for the Plastics Industry
The U.S. plastics industry employed just under one million workers in 2020 and continues to grow and expand. Leading the way in production and employment are Texas, Ohio, and California. In addition to environmental and safety issues, health hazards associated with the production of plastic products are a concern and should be recognized.
Man manufacturing upvc frame
Types and Characteristics of Commonly Used Plastics
The major types of plastic are classified as thermosets, elastomers, and thermoplastics. Thermosets are heated and require a curing agent which results in a permanent form that cannot be reground and reused. Elastomers can return to the original shape and size after deformation but are not formed by the same process as rubber. Thermoplastic polymers (resins) are widely used because they can be re-ground and re-molded; thereby eliminating waste and reducing production costs.
The most common thermoplastic polymers in use include:
Polyethylene
Polypropylene
Polyvinyl chloride (PVC)
Polystyrene
Acrylonitrile-butadiene- styrene (ABS)
Styrene acrylonitrile
Styrene-butadiene copolymers
Prior to molding, thermoplastic resins are mostly inert and present a low health risk except for any unreacted residual monomers, or molecules that bond together to form the polymer structure. A striking example of the effects of overexposure to resin dusts occurred in the 1970s when several workers who handled PVC resins were diagnosed with angiosarcoma, a rare liver disease. A significant reduction in exposure that lowered the risk for the development of disease was achieved when controls were applied to reduce the amount of unreacted monomer present in PVC resins. The levels went from as high as 1 percent to 0.001 percent.
Other sources of exposure can occur when the additives are combined with the resins to produce specific properties for the end product. Ideally, this occurs in a closed-looped system that exhausts the dust and minimizes exposure. In smaller operations, this is often not the case.
Additives are added to modify the properties of resins, aid in the molding process, and provide color. Common additives include flame retardants, antioxidants, blowing agents, optical brighteners, antistatic agents, UV light absorbers, fillers, solvents, curing agents, and reinforcements. Nearly 2,500 different chemicals are used in the production of additives. Additive compounds that commonly pose risks include:
Phthalates in plasticizers
Antimony, boron, bromine compounds in flame retardants
Hydrochlorofluorocarbons (HCFCs) and azodicarbonamide in blowing agents
Toxic heavy metal compounds (lead, cadmium, and chromium) in colorants
Thermal degradation products from organic colorants that are used as alternatives to metal compound colorants
Hazards During the Molding Process
The next phase where hazards exist is during the molding process, when the mold is released, and during purging and maintenance. Purging is performed whenever there is a resin or color change, or maintenance is needed on equipment. During purging, higher than usual molding temperatures are needed to clear the equipment of residue, and smoke is produced that may contain thermal degradation products from the resin and additives.
To protect workers, it is necessary to provide adequate exhaust ventilation in and around molding lines. If ventilation controls are inadequate in controlling dust levels during mixing, mists and vapors during mold release, or smoke generated during purging, occupational exposures should be assessed.
Sampling Strategy
The starting point for designing a good strategy for sampling is to review Safety Data Sheet (SDS) information for the resin and additives used in the process to determine regulated components and thermal degradation products. Some examples of constituents that are commonly assessed during personal sampling include the following:
Butane- contained in n, and acrolein in polypropylene resins
Hydrogen chloride in PVC resins
Styrene contained in polystyrene
Phenols and butadiene contained in ABS resins
Nuisance dust
When results from sampling are available, it can be determined if exposures have exceeded occupational exposure limits (OELs) established by the Occupational Safety and Health Administration (OSHA), the American Conference of Governmental Industrial Hygienists (ACGIH), and the National Institute of Occupational Health and Safety (NIOSH). If exposures exceed OELs, the proper respiratory protection can be provided to the workers in accordance with the OSHA Respiratory Protection standard but should be used only as a stopgap before control measures can be implemented and tested for effectiveness.
Noise Exposure
Another health hazard to consider in the plastics industry is noise exposure. It is common for noise exposures to exceed the OSHA Action Level (AL), which is 85 “A”-weighted decibels (85 dB(A) for hearing conservation.
In a typical operation, there is a high density of noise sources such as motors, fans, hydraulic pumps, and other equipment. Depending upon the size of the operation, exposures can even exceed the Permissible Exposure Limit (PEL) of 90 dB(A), and when that occurs, engineering and/or administrative controls are needed to reduce exposures.
Personal noise exposures are easily assessed utilizing calibrated noise dosimeters that record and average sound levels throughout the work period. The data logged is then used to determine the 8-hour time-weighted average exposure which can then be compared with the AL and PEL.
Further Information
Cornerstone serves clients that produce plastic products or packaging used by the food and beverage industry, health and beauty products, and a variety of consumer goods. Our Health and Safety department can perform a Personal Exposure Assessment to observe operations, job tasks, and work practices for air, noise, and ergonomic safety. Our experts provide reports of risks, prioritize areas for changes, and recommend control measures. Contact Cornerstone at info@corner-enviro.com or on our website for more information.
Mary Dunlap CIH, is a Senior Industrial Health and Safety Specialist and Certified Industrial Hygienist. She works with Cornerstone’s clients to develop exposure assessment strategies tailored for their work environments. She regularly performs ergonomic assessments using a variety of OHA and NIOSH tools to rate severity of risk for work related to musculoskeletal disorders.
References:
Recognition of Health Hazards in Industries – Second Edition, William A. Burgess
The Hazards of Plastic Injection Molding and Recommended Engineering Safety Controls – Sentry Air Systems
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The Value of Ergonomics for your Business
By Mary Dunlap, CIH Ergonomics, defined simply, is fitting a job to a person to reduce the risk of strains and injury to muscles, tendons, and ligaments, also known as musculoskeletal disorders (MSDs). The human costs are the best reason for preventing MSDs, but the financial burden to businesses cannot be underestimated. A 2018 survey of days away from work from the U.S. Bureau of Labor Statistics determined that 30 percent of cases were due to MSDs and that MSD cases require 38 percent more lost time days than typical injuries and illnesses. The direct costs associated with a sprain, strain, or hernia type injury can cost a business between $28,000 and $32,000 for medical treatment to resolve the injury. However, the medical costs are only part of the story and do not include indirect costs such as work stoppage, overtime, training of new employees, legal costs, and increased insurance premiums.
What are the benefits of ergonomics programs?
In addition to keeping workers healthy, there are many added benefits to implementing an ergonomics program that ultimately can make a business more profitable and attractive to potential business partners, highly qualified new employees, and outside investors, including:
Reduced costs associated with treating MSDs
Reduction in lost workdays and the length of long-term absences
Lower employee turnover and costs associated with replacing an employee
Higher employee engagement and focus on work quality
Increased productivity and efficiency
Reduced costs for correcting defects
Creating a safety record that is attractive to lenders and outside investors
When ergonomics is regarded as an important part of the operational process, employee engagement is enhanced, as is productivity and work quality. When an employer places value on the ability to perform the job comfortably and efficiently, employees feel respected. From this respect, workers are much more likely to be engaged in their work. With this engagement, comes regard for the quality of work they produce and a willingness to participate in improving processes and performing the work more efficiently. It has been estimated that even a simple improvement can result in a one-percent increase in quality and a five-percent increase in productivity. As attention to detail increases, the defect rate goes down and, with that, the costs for correcting the defects. Safety and sustainability have become very important aspects of how companies operate and are key environmental, social, and governance (ESG) indicators that lenders and investors consider when assessing business performance, assigning corporate credit ratings, and considering new investment opportunities. It is common practice for investors and lenders to request disclosure of injury rates. The top 29 companies that have earned safety culture awards have been found to consistently outperform the S&P 500 stock index.
What are the risks of workplace injuries?
The major risk factors for musculoskeletal disorders are:
forceful exertions involving with lifting, lowering, carrying, pushing, and pulling
repetitive movements, encountered when job cycles are less than 30 seconds long and when the cycle is repeated two or more times in a minute
awkward postures that result from poor equipment or the workspace design, not having the right tool to perform a job, and lack of worker awareness of how to properly move and position their body when performing a task.
Of these factors, the Occupational Safety and Health Administration (OSHA) has estimated that 25 percent of non-fatal occupational injuries result from forceful exertions primarily associated with material handling. The costs associated with treating MSDs can be significant when an injury occurs. Such injuries often result in multiple trips to a doctor or clinic, physical therapy appointments, and even surgery. In addition to treating the injury, lost workdays and sometimes long-term absences create staffing issues which increase overtime costs and losses in production. Additionally, job duties sometimes require modification to accommodate an employee who has been injured. When job tasks remain at risk for injury, there are not only lost workdays directly related to injuries but often there is also an increase in “casual absenteeism”. When strains or injuries are common, workers simply do not want to do the job. As dissatisfaction increases, so does the rate of employee turnover and the costs for replacing an employee. On average, it costs a business 20-50 percent of an employee’s salary to find and train a new employee replacement.
What is included in an ergonomics program?
Ergonomics programs and tools can make a big difference in the comfort, safety, and well-being of workers as well as add money to your bottom line? Actions can range from the simple to the complex and may include:
Implementing a daily stretching program for employees
Frequently rotating workers that perform repetitive jobs during a shift
Providing work surfaces that are the right height for the job
Reducing reach distances for parts or tools
Providing the right tools and equipment such as lift assist devices
Designing new workstations and equipment to best fit workers and their job tasks.
Coach and train employees how to properly position their bodies when lifting and performing tasks to avoid strains and injuries.
Further information
Cornerstone’s Health and Safety department can perform a Worksite Analysis to observe operations, job tasks, and work practices for ergonomic safety. As a Certified Industrial Hygienist, I can provide reports of risks, prioritize areas for changes, and recommend control measures. Contact Cornerstone at info@corner-enviro.com or on our website for more information. Mary Dunlap, CIH, is a Senior Industrial Health and Safety Specialist and Certified Industrial Hygienist. She works with Cornerstone’s clients to develop exposure assessment strategies tailored for their work environments. She regularly performs ergonomic assessments using a variety of OSHA and NIOSH tools to rate severity of risk for work related to musculoskeletal disorders.