Although exposure to specific forms of nickel differs among using and producing industries, the main exposure routes of toxicological relevance – inhalation and, to a lesser extent, skin contact – are the same in both industries.
The wide range of occupations with direct exposure to nickel via these routes of exposure are summarized below within 13 different industrial sectors. These sectors are:
- refining, main part of the refining processes;
- last stage refining, handling of primary nickel;
- alloy production, melting and foundry techniques;
- alloy production, powder metallurgy;
- batteries, nickel metal as feedstock;
- batteries, unknown type of nickel species as feedstock;
- nickel catalysts, nickel metal as feedstock;
- nickel catalyst, unknown type of nickel species as feedstock;
- nickel in the production of chemicals;
- contact with coins;
- contact with tools and other nickel releasing surfaces;
- use of batteries; and
- use of catalysts.
The first two sectors correspond to the nickel- producing industry, while the rest belong to the nickel-using industry.
Current exposures for all the industry sectors noted above are summarized in Table 3-1. Current data–generally acquired over the past 10 to 20 years, but occasionally representing data recorded since the late 1970s–typically represent actual measurements derived from standard procedures of ‘total’ aerosol sampling (e.g., through methods developed by the UK’s Health and Safety Executive or the US’ National Institute of Occupational Safety and Health). The data for this table come from a variety of sources including:
- published, peer-reviewed literature,
- company or agency reports in general circulation,
- company or agency internal reports not in general circulation but accessible through those organizations,
- company or agency databases and log-books obtainable through direct personal contacts, and
- follow-up through direct personal contacts (where appropriate and feasible) to fill gaps in information relevant to the evaluation.
From this table, it can be seen that exposures in the nickel-producing sectors have generally been reduced over time so that they now tend to be lower than in the using sectors, although there are some exceptions. For example, average exposures in primary nickel refining tend to be relatively low (around 0.07 mg Ni/m3), whereas average exposures in chemical blending and nickel catalyst production average 0.3-0.5 mg Ni/m3.
It is also clear from Table 3-1 and the footnotes to this table that the range of exposures in any given industry sector can vary widely. Workers employed in some jobs and activities in a sector with generally low exposures could well be exposed for days, weeks, or even years to levels of nickel aerosols well above those of some workers employed in another sector which experiences generally high exposures. Thus, it is unwise to regard occupational exposures within sectors as uniform among jobs, among workers within jobs, or within workers from day to day, without gathering further data on the particular industry sector of concern.
While it is clear that certain forms of nickel tend to predominate in different industry sectors (e.g., soluble nickel in plating), it appears that in no industry sector are workers exposed purely to one form of nickel. Hence, an understanding of the health effects of individual nickel species cannot be obtained from human data alone. Animal and human data, in conjunction with mechanistic studies, need to be considered as part of the weight-of-evidence required for determining species- specific occupational exposure limits. In addition, although little is currently known about the effects of particle size relative to speciation, it should be borne in mind that the size of the nickel particles to which workers are exposed is likely to play an important role in the biological effects of different nickel species. To the extent that such data are available, they are discussed in this document.