Knowledge of general exposure conditions within the workplace is another element of a good worker protection program. Workplace surveillance entails understanding applicable legislative/regulatory occupational exposure limits and implementing an air monitoring program that allows for the comparison of worker exposures to these limits. It is necessary for the employer to keep abreast of current recommended and mandated exposure limits regarding nickel and its compounds and to ensure that workplace exposures comply with these limits.
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 recordkeeping.
Specific requirements for each of these components may differ from country to country. Employers should consult the appropriate government agency and/or code for detailed procedures on establishing an air monitoring program. Air monitoring is not an end in itself but should be considered part of an overall program of risk assessment and management. It is necessary to evaluate monitoring results and decide whether any action is required to modify the sampling procedures or working environment.
When monitoring, it is important that the sampling strategy be flexibly designed to account for differences in worker and job variability. This means that different sampling strategies may need to be employed in different areas of a plant. It is also important to note that while either personal or static sampling devices may be used (provided that regional regulations do not stipulate a particular method), personal sampling is best suited to evaluating worker exposure while static sampling is a preferred tool for data collection for engineering controls. In all cases, the employees’ support should be sought by explaining the reason for sampling and asking for their participation.
Recently, the search for a more rational, health- related aerosol sampling has resulted in the development of an inhalable sampler at the Institute of Occupational Medicine. This sampler takes into consideration the efficiency of inhalation of the human head and the deposition of particles in the nasopharyngeal, thoracic and alveolar regions of the respiratory tract.
Side-by-side comparisons of the inhalable sampler to “total” aerosol samplers (such as the 37 mm sampler) have shown the inhalable sampler to consistently measure 2-3 times more aerosol than the “total” sampler. The observed biases tended to be greater for workplaces where aerosols are coarser.
As noted above, 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. Research projects currently underway are designed to provide new methods and means for collecting biologically-meaningful aerosol fractions. In fact, the American Conference of Governmental Industrial Hygienists (ACGIH) set its 1998 Threshold Limit Value (TLV) recommendations for nickel compounds based upon the “inhalable” particulate fraction. Countries that use the ACGIH TLVs to set their own Occupational Exposure Limits will be likely to make the appropriate changes. In the interim, it may be prudent to begin a program of evaluating the use of an inhalable dust fraction sampler, obtain measurements of particle size distribution, and to determine nickel species in samples when reasonably practicable.
Good industrial hygiene practice requires that an employer provide the sampled employees (and those unsampled employees whose exposures they are deemed to represent) with their personal sampling results and an explanation of their meaning. Group results should also be shared with the workforce. Where the results of sampling “representative” individual(s) are made available to other workers, consideration should be given to withholding personal identifiers. Exposure recordkeeping requirements may vary from country to country; hence, it is advisable to consult with the appropriate authority for details on possible mandatory requirements. Like health data, exposure monitoring data should be subject to rigorous quality control.