SAFE USE OF NICKEL IN THE WORKPLACE
Last Revised: 5/1997
8. CONTROL MEASURES 8.1 ENGINEERING CONTROLS
8.1.1 EXHAUST VENTILATION
8.1.2 DILUTION VENTILATION
8.2 ADMINISTRATIVE CONTROLS
8.3 WORK PRACTICE CONTROLS
8.4 PERSONAL PROTECTIVE EQUIPMENT (PPE)
8.4.1 RESPIRATORS
8.4.1.1 RESPIRATOR SELECTION
8.5 REFERENCES
Whenever conditions suggest high exposures or monitoring indicates a potential for an overexposure, measures to control exposures should be taken. Control options fall into four categories:
- engineering controls,
- administrative controls,
- work practice controls, and
- personal protective equipment (PPE).
Typically, engineering, administrative, and work practice controls are preferred over PPE when feasible. Since regulatory authorities may differ in their definition of "feasible" controls, employers should contact their respective authority for specific guidelines. Feasibility issues fall into two categories: technological feasibility and economic feasibility. Technological feasibility can generally be determined by examining the use of the technology in similar industries or for similar processes. Independent studies available from regulatory agencies, trade associations, other industry support groups, or reported in journals or other publications can also shed light on the issue. Determination of economic feasibility may require that a facility- or company-specific impact evaluation be made. Employers should be aware that regulatory authorities may already have determined that feasible engineering controls to achieve the OEL are available for particular industries or types of operation.
Three categories of engineering controls are generally considered - substitution, enclosure, and exhaust ventilation. Substitution may involve replacing the actual contaminant or replacing the source of the contaminant with one that produces lower concentrations. One consideration in substitution is to avoid introducing a new hazard when replacing the original hazard. Enclosure can mean either enclosing the source or the exposed individual. The source may also be remotely located so that little or no exposure results. Of the three engineering controls, however, ventilation is the most relevant to this document and, hence, is discussed in greater detail below.
Local exhaust ventilation provides contaminant capture or dispersion at or near the source. This form of ventilation can range from the very simple, i.e. the use of fans, to the more complex, such as the use of an exhaust hood positioned at the source. In all instances, the goal is to blow or draw the contaminant away from the breathing zones of the workers. Examples of local exhaust ventilation include:
- exhaust fans positioned over furnaces,
- exhaust hoods for points of transfer on dusty operations,
- slot hoods for electroplating tanks,
- ventilated metal spraying booths,
- downdraft tables for finishing (grinding) of cast iron pieces, and
- portable exhaust hoods for welding operations.
Ventilation design is a complex and expensive process that needs to be undertaken by suitably trained engineers who are familiar not only with industrial ventilation design but also with methods used to control exposures and protect worker health. The designer should consider: (1) the regulations that govern the release of the workplace contaminant to the surrounding environment, and (2) the process operation, including any materials used and the frequency with which they are handled. Particular attention should be paid to packaging processes involving fine materials. With respect to process operations, it is less expensive and more effective to use specialized and dedicated equipment introduced at the design stage than to retro-fit such equipment to an existing facility.
Dilution ventilation relies on adequate circulation of fresh air in the room to dilute the contaminant concentration. This type of ventilation has a number of limitations:
- workers close to the air contaminant's source may be exposed to high, localized concentrations of the contaminant,
- dilution ventilation systems are affected by weather conditions (doors or windows are kept open or closed depending on the temperature) and the movement of objects and people in a room, and
- if the rate of contaminant generation increases, the dilution supplied may be inadequate.
Given these limitations, such systems are usually not recommended for contaminants that are highly or moderately toxic.
Administrative controls reduce the exposure duration of individuals, thereby reducing the employee's overall exposure. Two alternatives are employee rotation and work shift modification. There are, however, drawbacks to these controls including:
- it may not be feasible to rotate employees with sufficient frequency to comply with the exposure limit (more frequently than every two hours is generally considered to be infeasible),
- the workers may not be versatile enough to perform different jobs, and
- greater management involvement is required.
Modifications in shift patterns are never easy. Effective exposure reduction by these techniques also requires that a constant contaminant level be present. For intermittent processes or where production rates vary between shifts, the differing levels of activity cause fluctuations in contaminant concentrations that may make average exposures difficult to quantify or predict. Because of these limitations, administrative controls should be considered secondary to engineering controls and other work practices that may be more effective in controlling exposures.
Work practice controls are procedures that serve to limit employee exposures. The effectiveness in reducing exposures thus relies heavily on worker training and the use of standard operating procedures. Some examples of good work practices are the routine use of available local exhaust ventilation, the use of wetting agents to reduce dust levels, and observing good housekeeping and personal hygiene practices. Housekeeping practices should include routine cleanup of the work area, particularly for dusty processes. However, the clean up activities themselves should not raise dust that may increase exposures. For example, dry sweeping may need to be prohibited and replaced by vacuum cleaning systems fitted with appropriate filters.
Good personal hygiene is important in all jobs and should be encouraged. Employees should be encouraged to change contaminated clothing in order to reduce the risk of contact dermatitis and of inhalation of nickel-bearing dust from contaminated clothing. If necessary, changes of work clothing and shower facilities should be made available. In areas where moisture, exposure to solvents, or wet working increases skin irritation and, thus, the possibility of developing nickel sensitization, appropriate protective clothing should be provided.
Particular attention should be given to the selection and maintenance of gloves. Some latex gloves can cause their own form of allergic contact dermatitis called latex glove contact urticaria (LGCU). LGCU can be avoided by wearing gloves made from polyvinyl chloride or synthetic rubber or by wearing cotton or plastic undergloves (Turjanmaa and Reunala, 1991). Once gloves or gauntlets impervious to soluble salts, their solutions, and/or powders have been selected, they should be washed and tested for leaks daily and replaced whenever found to be faulty.
Because smoking is the most common cause of respiratory cancer, it should be discouraged, if not banned. Appropriate educational materials and smoking cessation programs can play an important role in reducing cigarette smoking. In the interest of good hygiene, the consumption of beverages or food in nickel exposure areas should be discouraged, with attempts to confine such activity to designated eating areas. Some regulatory bodies have already mandated such practices. Hence, in EU countries, smoking, eating, and drinking are prohibited in areas where there is a risk of contamination by carcinogens.
8.4 PERSONAL PROTECTIVE EQUIPMENT (PPE)
PPE ordinarily is the last control option considered. Situations where use of PPE may be recommended include:
- while engineering controls are being installed,
- when current engineering controls are insufficient to reduce exposure to acceptable levels and administrative controls are not practical (the installation of additional feasible controls should be considered),
- when engineering and administrative controls are not feasible or practical or an emergency exists, and
- where intermittent, short-term exposures may not merit major engineering, e. g. in maintenance.
With respect to the latter situation, special attention should be paid to the use of PPE by maintenance personnel. Maintenance conditions typically differ from routine operations. For example, contaminant concentrations are frequently higher because of the very nature of the maintenance problem or because the ventilation system has been deactivated in order to allow the worker to perform the maintenance activity. Instituting certain work practice controls may be helpful in such circumstances, but additional personal protective equipment is frequently needed.
Emergency use of PPE requires additional planning and training. Special procedures for each potential emergency should be developed and practiced regularly.
Regardless of the situation in which PPE is used, the effectiveness of PPE in controlling exposures ultimately depends upon the correct selection and use of the equipment. As recommendations on this use may vary from country to country, employers should contact their appropriate regulatory authority for guidance. Use of PPE should always occur under a properly administered program.
The main types of protective equipment in use for nickel exposures are those designed to provide respiratory protection.1 Of particular importance is the use of respirators. Respirators may be used as an exposure control measure under certain circumstances. An appropriate authority should be consulted for guidance on respirator use (see below). Respirator use in fire fighting and similar emergencies is beyond the scope of this document.
1Although not specific to the nickel industry, the need for equipment to protect eyes, face, ears, head, and feet also may need to be considered, depending upon the task to be performed.
The first step in developing a program for the effective use of respirators is to establish a written policy, including the following:
- management and employee responsibilities,
- respirator selection,
- respirator fitting, including in some circumstances, fit-testing,
- employee instruction and training, including procedures for cleaning, inspection, maintenance, and storage,
- medical screening, and
- program evaluation.
Some jurisdictions have detailed rules for respirator use. The European Directive 88/656/EEC on the use of PPE governs the use of respirators in the EU. In the U. S., OSHA enforces Standard 1910.134 [29 Code of Federal Regulations (CFR) 1910.134] for respiratory protection of workers. In Canada, provincial government agencies have regional-specific requirements.
4 Although not specific to the nickel industry, the need for equipment to protect eyes, face, ears, head, and feet also may need to be considered, depending upon the task to be performed.
The criteria for selection should be clearly stated in the respiratory protection program. For nickel and nickel compounds, these should include such factors as the possible concentration of the contaminants present, the particle size(s) encountered, the toxicity of the chemicals, and the limitations of the respirators. The concentration of the contaminant will dictate whether a half-face, air purifying respirator is appropriate, or whether a higher level of protection, such as a supplied air respirator, is required. Once the employer has established that the hazardous conditions do not include oxygen deficiency, toxic gases, or atmospheres otherwise immediately dangerous to life and health, a determination of the protection needed should be calculated. The minimum protection factor needed is the ratio of the exposure concentration to the exposure limit. Any respirator tested should have a rated protection factor at least as large as this ratio (Table 5). Quantitative fit testing is required to ensure that the respirator performs as desired.
TABLE 5: PROTECTION FACTORS FOR RESPIRATORS USED FOR PARTICULATES
| Protection Factor | Respirator Type |
| 5 |
|
| 10 |
|
| 25 |
|
| 50 |
|
| 1,000 |
|
| 2,000 |
|
| 10,000 |
|
Source: National Institute for Occupational Safety and Health (1987).
Nickel and its compounds will generally be in particulate form such as dusts (solid particulate), mists (liquid condensation particulate), and fume (solid condensation particulate, usually as oxidized forms of nickel). Filters appropriate to each form are available as single-use respirators or in canisters and cartridges that attach directly to molded facepieces. In the case of powered, air-purifying respirators, the canisters are attached to the facepiece with a hose. The fit of a respirator with a molded facepiece is more readily determined than is the fit of a single-use respirator, but the latter is generally more comfortable.
High concentrations of the nickel compound may require the use of supplied air by either an airline or battery powered respirator or a self-contained breathing apparatus (SCBA). Airline respirators and battery powered respirators provide a continuous supply of air for long durations. The SCBAs, on the other hand, have a limited air supply (from 30 minutes to 4 hours), but allow for a greater degree of mobility and, because of the positive pressure, have a higher protection factor. Use of a SCBA requires significant training and a health assessment of the worker.
When selecting air purifying respirators, employers should consider assigning each employee his/her own respirator. Care and maintenance, thus, become a matter of personal importance, and the responsibility for the health of a worker is shared between employer and employee. Each employee should ensure that the respirator which is issued fits properly and, hence, provides the intended degree of protection. In some jurisdictions, respirator fit-testing is mandatory.
NIOSH. National Institute of Occupational Safety and Health. (1987). Guide to Industrial Respiratory Protection. DHHS (NIOSH) PB No. 87-116.
Turjanmaa, K. and Reunala, T. (1991). Contact urticaria to surgical and household rubber gloves. In: Menné, T. and Maibach, H. I., eds. Exogenous Dermatoses: Environmental Dermatitis. Boca Raton, Florida: CRC Press. pp. 317-326.
