Assessing the Risks of Workers Exposed to Nickel

Any efforts to evaluate occupational health risks such as those identified above must start with good data collection. This includes not only monitoring workplace exposures (discussed in greater detail in the next section), but assessing the health of individual workers with the ultimate goal of keeping the worker healthy and reducing the overall risks in the work environment. It is not enough to periodically monitor workers, but programs must be implemented in ways that allow for the systematic collection of data that can be used in epidemiological studies and, subsequently, risk assessment. In some countries, implementation of a health surveillance program is obligatory. In such instances, any company-based surveillance program should be in compliance with the relevant local/national guidelines. Developing infrastructure and systems that support consistent data collection and storage requires effort, careful planning, and an adequate allocation of resources.

The general steps involved in the assessment of risks include:

  • Determining the population at risk.
  • Identifying the hazards.
  • Assessing exposures and health outcomes.
  • Developing data collection and management systems.
  • Training and benchmarking.

For purposes of risk assessment, records should be kept on most, if not all, workers employed in the nickel industry. This includes not only production workers, but office workers and support staff as well. Consideration should also be given to contractors, such as temporary workers or long-term maintenance crews employed at factories, as some of these workers may be employed in potentially high exposure jobs. Companies should assign a unique identifier to each individual.

It is also important to identify all potentially harmful substances in a workplace and to monitor and control exposures in order to manage the risk. All the nickel species present in an industrial setting should be identified, and a complete inventory of raw materials used, materials produced, by-products, and contaminants should be taken. Consideration should be given to monitoring these materials not only under normal operations, but also when short-term peak exposures occur (e.g., during maintenance). In addition, a record should be made of all procedures and equipment used (including control equipment such as local exhaust ventilation and respirators), changes in processes, and changes in feed materials. Complementing this description of the worksite should be a description of each worker’s employment history, both past and current.

With respect to exposures, two types of exposure data are required: those that pertain to the ambient environment (e.g., workplace air) and those that pertain to the internal environment of the worker (e.g., health surveillance). To be of use in risk assessment, each must be linked to the other. Health surveillance may be used to evaluate an individual’s health prior to, during, and at termination of employment. Occasionally, it also may be used during retirement. Considerable clinical skill and judgment are required to assess work- related health effects. Consultation with properly trained personnel is critical. Issues such as the invasiveness, sensitivity, and accuracy of testing procedures must be considered carefully, as should the rights of the workers. Laws regarding discriminatory practices in hiring and job placement should be strictly followed, as should laws regarding recordkeeping. Any health data gathered and recorded should be subject to rigorous quality control.

In structuring a health surveillance program, consideration ideally should be given to the following components:

  • Pre-placement assessment. Of particular importance is the identification of pre-existing medical conditions in target organs (notably the respiratory system and skin, but also reproductive and renal systems) that potentially might be affected by nickel and its compounds. A pre-placement assessment should typically include, but not necessarily be limited to: baseline health data, a detailed history of previous disease and occupational exposures, present or past history of allergies (particularly nickel-related) including asthma, identification of personal habits (most notably, smoking) and hobbies, a physical examination (which may include chest X-rays and other pulmonary tests), and evaluation of the ability of a worker to wear respiratory protection equipment.
  • Periodic assessment. Such an assessment generally consists of an update of the above, but may also include more extensive testing. Unless mandated more frequently by law, measurements of respiratory function and chest X-rays should be considered around every 5 years. Depending on the age, the smoking status, and the job task (nature and level of exposure), more frequent chest X-rays may be appropriate.

Skin patch testing is not recommended as a routine pre-employment procedure because there is a possibility that such test may sensitize the applicant. However, in special circumstances, such testing may be warranted for purposes of clinical diagnosis. Patch testing should only be undertaken by persons experienced in the use of the technique.

In many industrial health surveillance programs, workers may be monitored for markers of exposure in body fluids, with the intent of establishing a correlation between external exposure, internal exposure (as measured by the marker), and effect. However, in the case of nickel, a biological monitoring program should be implemented only after careful consideration of the facts and limitations of such a program. While of some value as a marker of exposure, nickel in urine, blood, and other tissues or fluids (with the exception of nickel carbonyl) has not been shown to be predictive of health risks. Given that biological monitoring reflects only the amount of solubilized nickel present in biological materials and not true body burden, its utility is questionable as an early warning device of potential health effects that are generally organ-specific, long-term, and accumulative in nature.

If implemented, a biological monitoring program should augment both environmental monitoring and industrial hygiene programs. It should never be implemented as a “stand alone” program. Given the above limitations, biological monitoring may have a place, but mainly in specific situations, e.g., where exposures are to soluble nickel compounds, fine nickel metal powders, or nickel carbonyl. It is less useful in situations where exposures are predominantly to insoluble compounds of larger particle size or where exposures are mixed. If biological monitoring is undertaken, urinary sampling is generally preferred over serum sampling because it is less invasive and easier to conduct.

It is preferable that any health surveillance program implemented be administered by qualified occupational health specialists. However, once a proper data collection system is in place, nonexpert staff, with appropriate training, can help to collect some of the data on a day-to-day basis.

Lastly, any surveillance program that is implemented should be evaluated to determime how well it is working. This entails establishing sound database management systems, filling recognized data gaps, and setting goals against which future evaluations can be made.