Adapted in part from an unpublished article by Simon Pickvance.
The iron and steel industry is a “heavy industry”: in addition to the safety hazards inherent in giant plants, massive equipment and movement of large masses of materials, workers are exposed to the heat of molten metal and slag at temperatures up to 1,800°C, toxic or corrosive substances, respirable air-borne contaminants and noise. Spurred by trade unions, economic pressures for greater efficiency and governmental regulations, the industry has made great strides in the introduction of newer equipment and improved processes which afford greater safety and better control of physical and chemical hazards. Workplace fatalities and lost-time accidents have been significantly reduced, but are still a significant problem (ILO 1992). Steel making remains a dangerous trade in which the potential hazards cannot always be designed out. Accordingly, this presents a formidable challenge to everyday plant management. It calls for ongoing research, continuous monitoring, responsible supervision and updated education and training of workers on all levels.
Musculoskeletal injuries are common in steel making. Despite the introduction of mechanization and assistive devices, manual handling of large, bulky and/or heavy objects remains a frequent necessity. Constant attention to housekeeping is necessary to reduce the number of slips and falls. Furnace bricklayers have been shown to be at highest risk of work-related upper arm and low back problems. The introduction of ergonomics into the design of equipment and controls (e.g., crane drivers’ cabs) based on study of the physical and mental requirements of the job, coupled with such innovations as job rotation and team working, are recent developments aimed at enhancing the safety, well-being and performance of steel workers.
Steel making is one of the noisiest industries, although hearing conservation programs are decreasing the risk of hearing loss. The major sources include fume extraction systems, vacuum systems using steam ejectors, electrical transformers and the arc process in electrical arc furnaces, rolling mills and the large fans used for ventilation. At least half of noise-exposed workers will be handicapped by noise-induced hearing loss after as little as 10 or 15 years on the job. Hearing conservation programmes, described in detail elsewhere in this Encyclopaedia, include periodic noise and hearing assessments, noise control engineering and maintenance of machines and equipment, personal protection, and worker education and training
Causes of hearing loss other than noise include burns to the eardrum from particles of slag, scale or molten metal, perforation of the drum from intense impulse noise and trauma from falling or moving objects. A survey of compensation claims filed by Canadian steelworkers revealed that half of those with occupational hearing loss also had tinnitus (McShane, Hyde and Alberti 1988).
Potentially hazardous vibration is created by oscillating mechanical movements, most often when machine movements have not been balanced, when operating shop floor machines and when using such portable tools as pneumatic drills and hammers, saws and grindstones. Damage to vertebral discs, low back pain and degeneration of the spine have been attributed to whole body vibration in a number of studies of overhead crane operators (Pauline et al. 1988).
Whole body vibration can cause a variety of symptoms (e.g., motion sickness, blurring and loss of visual acuity) which may lead to accidents. Hand-arm vibration has been associated with carpal tunnel syndrome, degenerative joint changes and Reynaud’s phenomenon in the finger tips (“white finger disease”), which may cause permanent disability. A study of chippers and grinders showed that they were more than twice as likely to develop Dupuytren’s contracture than a comparison group of workers (Thomas and Clarke 1992).
Heat exposure is a problem throughout the iron and steel industry, especially in plants located in hot climates. Recent research has shown that, contrary to previous belief, the highest exposures occur during forging, when workers are monitoring hot steel continuously, rather than during melting, when, although temperatures are higher, they are intermittent and their effects are limited by the intense heating of the exposed skin and by the use of eye protection (Lydahl and Philipson 1984). The danger of heat stress is reduced by adequate fluid intake, adequate ventilation, the use of heat shields and protective clothing, and periodic breaks for rest or work at a cooler task.
Lasers have a wide range of applications in steel making and may cause retinal damage at power levels far below those required to have effects on the skin. Laser operators can be protected by sharp focus of the beam and the use of protective goggles, but other workers may be injured when they unknowingly step into the beam or when it is inadvertently reflected at them.
Radioactive nuclides are employed in many measuring devices. Exposures can usually be controlled by posting of warning signs and appropriate shielding. Much more dangerous, however, is the accidental or careless inclusion of radioactive materials in the scrap steel being recycled. To prevent this, many plants are using sensitive radiation detectors to monitor all scrap before it is introduced into the processing.
Steel workers may be exposed to a wide range of pollutants depending on the particular process, the materials involved and the effectiveness of monitoring and control measures. Adverse effects are determined by the physical state and propensities of the pollutant involved, the intensity and duration of the exposure, the extent of accumulation in the body and the sensitivity of the individual to its effects. Some effects are immediate while others may take years and even decades to develop. Changes in processes and equipment, along with improvement of measures to keep exposures below toxic levels, have reduced the risks to the workers. However, these have also introduced new combinations of pollutants and there is always the danger of accidents, fires and explosions.
Dust and fumes
Emissions of fumes and particulates are a major potential problem for employees working with molten metals, making and handling coke, and charging and tapping furnaces. They are also troublesome to workers assigned to equipment maintenance, duct cleaning and refractory wrecking operations. Health effects are related to the size of the particles (i.e., the proportion that are respirable) and the metals and aerosols that may be adsorbed on their surfaces. There is evidence that exposure to irritant dust and fumes may also make steelworkers more susceptible to reversible narrowing of the airways (asthma) which, over time, may become permanent (Johnson et al. 1985).
Exposures to silica, with resultant silicosis, once quite common among workers in such jobs as furnace maintenance in melting shops and blast furnaces, have been lowered through the use of other materials for furnace linings as well as automation, which has reduced the number of workers in these processes.
Asbestos, once used extensively for thermal and noise insulation, is now encountered only in maintenance and construction activities when formerly installed asbestos materials are disturbed and generate airborne fibres. The long term effects of asbestos exposure, described in detail in other sections of this Encyclopaedia, include asbestosis, mesothelioma and other cancers. A recent cross-sectional study found pleural pathology in 20 out of 900 steelworkers (2%), much of which was diagnosed as restrictive lung disease characteristic of asbestosis (Kronenberg et al. 1991).
Emissions generated in steel making may contain heavy metals (e.g., lead, chromium, zinc, nickel and manganese) in the form of fumes, particulates, and adsorbates on inert dust particles. They are often present in scrap steel streams and are also introduced in the manufacture of special types of steel products. Research carried out on workers melting manganese alloys has shown impaired physical and mental performance and other symptoms of manganism at exposure levels significantly below the limits currently allowable in most countries (Wennberg et al. 1991). Short-term exposure to high levels of zinc and other vaporized metals may cause “metal fume fever”, which is characterized by fever, chills, nausea, respiratory difficulty and fatigue. Details of the other toxic effects produced by heavy metals are found elsewhere in this Encyclopaedia.
Acid mists from pickling areas can cause skin, eye and respiratory irritation. Exposure to hydrochloric and sulphuric acid mists from pickling baths have also been associated in one study with a nearly twofold increase in laryngeal cancer (Steenland et al. 1988).
The predominant source of sulphur emissions in steel making is the use of high-sulphur fossil fuels and blast furnace slag. Hydrogen sulphide has a characteristic unpleasant odour and short-term effects of relatively low-level exposures include dryness and irritation of nasal passages and the upper respiratory tract, coughing, shortness of breath and pneumonia. Longer exposures to low levels may cause eye irritation, while permanent eye damage may be produced by higher levels of exposure. At higher levels, there may also be a temporary loss of smell which can delude workers into believing that they are no longer being exposed.
Oil mists generated in the cold rolling of steel can produce irritation of skin, mucous membranes and upper respiratory tract, nausea, vomiting and headache. One study reported cases of lipoid pneumonia in rolling mill workers who had longer exposures (Cullen et al. 1981).
Polycyclic aromatic hydrocarbons
PAHs are produced in most combustion processes; in steelworks, coke making is the major source. When coal is partially burnt to produce coke, a large number of volatile compounds are distilled off as coal tar pitch volatiles, including PAHs. These may be present as vapours, aerosols or adsorbates on fine particulates. Short-term exposures may cause irritation of the skin and mucous membranes, dizziness, headache and nausea, while long-term exposure has been associated with carcinogenesis. Studies have shown that coke-oven workers have a lung cancer mortality rate twice that of the general population. Those most exposed to coal tar pitch volatiles are at the highest risk. These included workers on the oven topside and workers with the longest period of exposure (IARC 1984; Constantino, Redmond and Bearden 1995). Engineering controls have reduced the numbers of workers at risk in some countries.
Over 1,000 chemicals are used or encountered in steel making: as raw materials or as contaminants in scrap and/or in fuels; as additives in special processes; as refractories; and as hydraulic fluids and solvents used in plant operation and maintenance. Coke making produces by-products such as tar, benzene and ammonia; others are generated in the different steel-making processes. All may potentially be toxic, depending on the nature of the chemicals, the type, the level and duration of the exposures, their reactivity with other chemicals and the susceptibility of the exposed worker. Accidental heavy exposures to fumes containing sulphur dioxide and nitrogen oxides have caused cases of chemical pneumonitis. Vanadium and other alloy additions may cause chemical pneumonitis. Carbon monoxide, which is released in all combustion processes, can be hazardous when maintenance of equipment and its controls are substandard. Benzene, along with toluene and xylene, is present in coke-oven gas and causes respiratory and central nervous system symptoms on acute exposure; long-term exposures may lead to bone marrow damage, aplastic anaemia and leukaemia.
High levels of work stress are found in the steel industry. Exposures to radiant heat and noise are compounded by the need for constant vigilance to avoid accidents and potentially hazardous exposures. Since many processes are in continuous operation, shift work is a necessity; its impact on well-being and on workers’ essential social support are detailed elsewhere in this Encyclopaedia. Finally, there is the potent stressor of potential job loss resulting from automation and changes in processes, plant relocation and downsizing of the workforce.
Protecting steel workers against potential toxicity requires allocation of adequate resources for a continuing, comprehensive and coordinated programme that should include the following elements:
- assessment of all raw materials and fuels and, when possible, substitution of safer products for those known to be hazardous
- effective controls for the storage and safe handling of raw materials, products, by-products and wastes
- continuous monitoring of workers’ personal occupational environment and ambient air quality, with biological monitoring when required, and periodic medical surveillance of workers to detect more subtle health effects and verify fitness for their jobs
- engineering systems to control potential exposures (e.g., equipment enclosures and adequate exhaust and ventilation systems) supplemented by personal protective equipment (e.g., shields, gloves, safety glasses and goggles, hearing protectors, respirators, foot and body protection, etc.) when engineering controls do not suffice
- application of ergonomic principles to design of equipment, machine controls and tools and analysis of job structure and content as a guide to interventions that may prevent injury and enhance workers’ well-being
- maintenance of readily available, up-to-date information about potential hazards, which must be disseminated among workers and supervisors as part of an ongoing worker education and training programme
- installation and maintenance of systems for the storage and retrieval of the voluminous health and safety data, as well as for the analysis and reporting of records of inspection findings, accidents and worker injury and disease.