Where workers are known to be exposed to nickel in the air, it is necessary to conduct air monitoring in order to determine whether worker exposures fall within permissible limits. A successful air monitoring program begins with a good understanding of the physical layout and processes of the workplace. Before any monitoring is undertaken, a visual survey of the site should be conducted in order to identify potential areas of significant exposure. Material Safety Data Sheets (MSDS) should also be reviewed and discussed with employees as another means of identifying potential problem areas. Only when these initial surveys have been completed and analyzed should the employer embark on an air monitoring program.
Characterization of exposure is a complex task that is best done by trained personnel. For facilities that lack the appropriate staff, certified occupational hygiene consultants are the suggested alternative. Governmental organizations may provide assistance on air monitoring or advice on where to obtain skilled help.
The components of an air monitoring program are:
- development of a sampling strategy,
- purchase or rental of sampling equipment and supplies,
- calibration of equipment,
- sample collection,
- sample analysis,
- calculation of exposure concentrations,
- determination of compliance status,
- notification of employees of the results, and
- documentation and record-keeping.
Specific requirements for each of these components may differ from country to country; therefore, employers should consult the appropriate government agency or code for detailed procedures.
Air monitoring is not an end in itself but should be considered part of an overall program of risk assessment and management. Upon completion of an air monitoring survey, it is necessary to evaluate the results and decide whether any action is required to modify the sampling procedures or working environment.
Current nickel standards generally differentiate only between water-soluble and insoluble compounds and nickel carbonyl. Thus, the application of air monitoring techniques that collect total dust samples in combination with analyses that distinguish between compound solubilities has been sufficient to determine compliance. Recent work, however, indicates that health effects associated with nickel exposures may be dependent upon a number of factors, including chemical form (speciation), particle size, and solubility within biological fluids (as opposed to water) (see Section 5). Therefore, it is recommended that each worksite be characterized with regard to the individual nickel species present in the air and to the distribution of particle sizes in the aerosols.
New sampling instruments have been developed that measure inhalable aerosol (Mark and Vincent, 1986). The performance of these devices closely matches the human inhalation curves, adopted by the International Standards Organisation (ISO, 1984), the Comité Européen Normalisation (CEN, 1993) and the American Conference of Governmental Industrial Hygienists (ACGIH, 1993-94). The ACGIH replaced the traditional ‘total’ aerosol concept with a new sampling convention based on human inhalability in their 1998 TLV recommendations for nickel. It should be noted that side-by-side comparisons of the inhalable sampler to “total” aerosol samplers (such as the 37 mm sampler) have shown that the inhalable sampler consistently measures 2-3 times more nickel aerosol than the ‘total’ sampler. (Tsai et al., 1995; Tsai et al., 1996a and 1996b).6 Consequently, when epidemiological data based upon “total” measurements form the basis of a hazard identification conversions of the results will have to be performed to establish new guidelines for using “inhalable” measures (i.e., the “total” values will have to be increased to account for the greater efficiency of the “inhalable” sampler).
(6) More information on this research is available from NiPERA.
The components of an air sampling program are briefly discussed below.
Calculating Exposure Results