Working in the primary metal industries can be a hazardous occupation. The making and shaping of iron, steel, aluminum, and other metals involves heat, pressure, the movement of molten metals, and other activities that can expose workers to numerous physical and chemical hazards. Heat, noise, radiation, vibration, airborne particles, space restrictions, hazards from falling objects, electrical shock, and molten metal are just a few examples of hazards that workers may be exposed to. And this is just the tip of the iceberg when it comes to potential hazards during the production of metals and metal casting.
This blog will review some of the more common hazards encountered during smelting and casting applications, as well as other activities associated with the primary metal industries.
In the United States, recordable injury and illness rates are higher for the primary metal industries than many other industries including oil and gas extraction, mining, and construction. In 2020, the incidence rate for primary metals was 3.9 incidents per 100 full-time employees, compared to 2.9 for all industries.[1]
The primary metal industries experienced over 14,000 recordable injuries and illnesses, in 2020. Over 9,000 of these incidents resulted in days away from work, job restrictions, or job transfer.[2]
Aluminum foundries experienced an incidence rate of 8.4, the highest among primary metals industries, and the 13th highest incident rate of any NAICS code. Iron foundries had an incident rate of 7.3 and steel foundries 6.7.[3]
What are Some of the Potential Hazards for Workers in Molten Metal Industries?
There are many potential hazards within the molten metal industries, including:
- Airborne chemical hazards – Chemicals in the workplace that workers are exposed to by inhalation.
- Noise – In smelting and casting, noise levels may quickly reach levels that may be hazardous and make it necessary to implement controls.
- Eye hazards and radiation – During smelting and casting activities there may be a risk of flying particles, sparks, and optical radiation.
- Falling objects – Due to the overhead hazards there is a real risk of being struck by falling objects or hitting your head on other objects.
- Heat and molten metal – Heat and molten metal are present throughout the metal production and casting process. Depending on how close workers are to the melt or furnace, additional protection including protective clothing may be needed to reduce exposure to radiant heat and molten metal splash.
What Production Processes are Involved in Heavy Manufacturing that Involves Molten Metals?
Before we get into the specific hazards, let’s take a high-level look at some of the production processes and associated hazards.
For steelmaking, the basic steps in the production process are coke production, iron making, steel making, refining, and casting. The hazards can include
- Potential respiratory hazards from metal dust and fume, combustion gases, and various contaminants generated during the coking process.
- Noise hazards from furnace operation and other activities, foreign body eye injuries as well as heat stress and radiant heat from molten iron and steel.
The basic steps of the aluminum production process are alumina production, anode production, aluminum smelting, and casting. The hazards can include:
- Potential respiratory hazards from alumina dust, fluorides, sulfur dioxide, and other contaminants that are generated during the smelting and anode production process.
- Noise hazards from furnace operation and other activities, foreign body eye injuries as well as well heat stress, and radiant heat from molten aluminum.
Foundry processes can vary depending on the metals and alloys used, and the type and size of castings produced. In general, the primary steps include mold and core making, melting and casting, shake-out/knock-out, and finishing and fettling. The hazards can include:
- Heat stress and radiant heat from the handling and pouring of molten metals.
- Inhalation of respirable crystalline silica, metal fume, and gases and vapors from fluxes, binders, release agents, and other additives.
- Noise hazards.
Noise Hazards and Hearing Protection Options
Exposure to loud noise is one of the most widespread hazards for people working in manufacturing industries, including primary metal production. Occupational noise exposure is the second most common risk factor in the workplace, and the most commonly reported occupational illness in many countries.[4]
Unlike many other workplace injuries or illnesses, the symptoms of overexposure to noise are often unnoticed until significant exposure has occurred and permanent damage to the hearing system has been done. There is no blood or visible damage and seldom any pain to warn people that there is a problem. In addition, damage to the hearing system occurs slowly over time and the early warning signs are easy to miss.[5]
It is estimated that 430 million people worldwide have disabling hearing loss, and on average, about 16% of adult-onset hearing loss is due to occupational exposure.[6] The global cost of unaddressed hearing loss is estimated at $980 billion/year, and noise is now being acknowledged as an important public health issue and a top environmental risk faced by the world today.[7]
Noise exposure levels during smelting and casting applications can vary widely and are influenced by the specific industry and equipment, surrounding environment, and processes used. Where hearing protection is chosen as a control measure, there is a broad range of products to consider.
Hearing protection covers a wide variety of style, design, and functionality, and range from simple disposable foam plugs to the more sophisticated communication headsets with built-in Bluetooth functionality for two-way communication.
Some earmuffs can be attached to industrial safety helmets or the rigid headtop of a powered and supplied air respirator system while others can be worn over the head or behind the head.
In primary metals and foundry industries where heat can be a major factor, earplugs are often preferred as earmuffs can get a little warm.
Respiratory Hazards and Respiratory Protection Choices
Smelting and casting applications can produce a wide variety of airborne contaminants which if inhaled in significant quantities, may lead to a number of acute and chronic health effects. There are many different airborne chemical hazards that may be present within the primary metals industry. These can include particulates such as metal dust and fume, silica, and polycyclic aromatic hydrocarbons, as well as gases and vapors such as Hydrogen Fluoride, Carbon Monoxide, Phenol, and formaldehyde. The potential health effects are wide and varied as well, and may include eye and respiratory irritation, occupational asthma, silicosis, COPD, and cancer.
When other controls are not effective or feasible, or when implementing other controls, respiratory protection can be used to help reduce worker exposure to airborne contaminants. A wide variety of respirator options are available for smelting and casting applications including filtering facepiece respirators, half and full facepiece elastomeric respirators, powered air-purifying respirators, and supplied air respirator systems. Certain powered and supplied air respirator systems feature integrated protection that combines respiratory protection, head protection, and eye and face protection.
Head Protection Considerations for Falling Objects
Metal production and foundries contain many risks from falling objects, or accidental impacts when working around or beneath objects or equipment.
Because of this, there is generally a mandatory industrial safety helmet or hard hat policy at most worksites. For workers who may be in close proximity to furnaces, molten metal, or other radiant heat sources, head protection designed to withstand higher heat loads may be necessary.
Due to the risk of injury from falling objects and other exposures, head protection is normally required for smelting and casting applications. Hard hats are available in a wide variety of colors, with attachments and accessories to help provide additional protection, including helmet covers and neck covers. It is important to select head protection PPE that is appropriate for the hazard and working conditions and meets appropriate performance standards.
Risks of Eye Injuries and Eye Protection Selection Information
The eye is a critical organ that many of us easily overlook when it comes to protection. Prevent Blindness America estimates that “eye injuries of all types occur at a rate of more than 2,000 per day. Of these, 10% to 20% will be disabling because of temporary vision loss”[8] It is estimated that 90% of these injuries were preventable in that the worker was either not wearing eye protection or not wearing the appropriate kind of protection for the tasks being performed. The source of these hazards can be ultraviolet, visible, and infrared radiation from molten metal and the melting process, contact with solid, liquid, or gaseous materials and foreign bodies, and mechanical impact from molten metal, slag, and high-velocity particles to the eyes and face. According to the US Bureau of Labor Statistics, approximately 31% of all eye injuries in the US are due to impact from flying objects or particles, and approximately 26% are due to foreign bodies in the eye.[9]
Exposure to ultraviolet radiation can lead to dry eyes, itchy eyes, and photokeratitis which is an inflammation of the cornea often referred to as “arc eye”.
These adverse health effects occur very quickly – after only milliseconds of exposure. Damage is immediate and accumulative and can lead to cataracts, lens damage, and blindness upon long-term overexposure. Chronic overexposure to UV radiation can also lead to malignant melanoma, a form of cancer.
Potential short-term symptoms from intense visible light are spot blindness, bloodshot eyes, and headache. Red eyes or bloodshot eyes occur when the blood vessels on the surface of the eye expand. Sometimes a blood vessel can leak and cause bleeding on the surface of the eye and leave a red patch.
These health effects from visible light overexposure take some time to happen – normally seconds to hours, and damage can be immediate and accumulative. Long-term overexposure may lead to problems with the macula, impaired vision at night, and permanent retina damage.
Overexposure to infrared radiation can also cause problems. Adverse health effects can include dry eyes, tearing eyes, and headaches. Prolonged exposure to infrared radiation can heat the lens of the eye and produce cataracts over the long term.
Health effects from IR radiation can take a long time to happen – usually years. Damage is accumulative and can lead to retinal damage and cataracts.
Foreign body eye injuries are also a concern during smelting and casting activities. Imagine you have been working hard for an hour grinding castings in a foundry. You take off your eye and face protection and wipe your brow on the sleeve of your shirt – which just happens to be covered in metal dust, grinding particles, and swarf, as well as abrasive particles, grains, and splinters – and these are accidentally rubbed into your eye.
Particles can also fall into the eyes from hair, clothing, or even items of PPE.
Gases, vapors, mists, and fine suspended dust in the air can cause irritation, inflammation, and other damage. Liquids can be splashed, sprayed, or get into the eye.
Corneal scratches caused by metal particles can cause serious eye injury. The eye can become inflamed, painful, and teary in reaction to the foreign object. Medical attention may be required to remove the foreign object, to wash out the eye, assess the damage, and apply treatment as required.
When it comes to mechanical hazards they are typically from sparks and molten metal, or high-speed particles resulting from finishing molds, surface preparation, removing sprues, and surface finishing. Another important consideration is the hazards associated with jumping tools and fragmenting discs.
Penetrating and blunt force injuries are often traumatic and painful. In most cases, they also require immediate medical attention. These injuries often lead to lost work time which will impact productivity.
Other health effects to the eyes and face may include impact trauma and lacerations from flying particles and burns from hot slag or particles.
There is a wide variety of eye and face protection PPE available. Everything from safety glasses and goggles, safety glasses with a foam gasket, clear and tinted faceshields, and headtops with powered and supplied air respirator systems. It is important to select products that are appropriate for the hazard and working conditions and meet appropriate performance standards. No personal protective equipment does any good if it is not being worn.
The time wearing the equipment, and wearing the equipment correctly, is imperative. PPE needs to be worn 100% of the time when exposed to hazards to be effective. There are also additional risks with smelting and casting including working at height and confined space entry. For more information about how to select the right PPE for your smelting and casting application needs, please do not hesitate to contact our 3M health and safety specialists today.
[1] U.S Bureau of Labor and Statistics 2020, https://www.bls.gov/iif/soii-data.htm
[2] U.S. Bureau of Labor and Statistics 2020, https://www.bls.gov/iif/soii-data.htm
[3] U.S. Bureau of Labor and Statistics 2020, https://www.bls.gov/iif/soii-data.htm
[4] World Report on Hearing, 2021, https://www.who.int/publications/i/item/world-report-on-hearing
[5] World Report on Hearing, 2021, https://www.who.int/publications/i/item/world-report-on-hearing
[6] World Report on Hearing, 2021, https://www.who.int/publications/i/item/world-report-on-hearing
[7] U.S. Bureau of Labor Statistics, Workplace Injuries Involving Eyes, 2008, https://www.bls.gov/opub/mlr/cwc/workplace-injuries-involving-the-eyes-2008.pdf
[8] Prevent Blindess America, https://preventblindness.org/wp-content/uploads/2011/12/FS14_SightSavers.pdf