Nickel sulphate in Blackfast 181
Firstly it should be pointed out that the research, which forms the basis of the new classification, carried out by the Rapporteur (Danish Environmental Protection Agency) was based purely on exposure in those industries that are major users of Nickel, i.e. nickel producing industries and nickel plating industries.
The category 1 carcinogenic classification of certain water soluble nickel compounds is linked only to inhalation (not by ingestion or dermal exposure). This means the issue is only relevant to occupational health in nickel-producing and certain nickel-using industries.
A cocktail of compounds exists in nickel refining situations and therefore the exact role of water soluble nickel compounds such as nickel sulphate or chloride, in terms of their contribution to cancer risk, has been unclear.
The recent risk assessment on Nickel, carried out by The Danish Environmental Protection Agency on which the EU classification is based, found as follows:
Respiratory exposure to nickel sulphate occurs only in an occupational exposure context, by inhalation of aerosols containing nickel sulphate, by definition an aerosol is an assemblage of small particles, solid or liquid, suspended in air.
Aerosols would commonly be created from a tank of liquid by bubbling air through it. As the air bubbles rise to the surface and break, small droplets of the solution are released into the air. Large drops fall back into the tank or deposit on surfaces nearby. Smaller droplets become airborne and drift into the general plant air where the workers can inhale them. Small droplets rapidly lose their water by evaporation, leaving behind solid particles made up of crystals of nickel salts and the other components of the bath. Blackfast 181 is not agitated and therefore should not be capable of producing aerosols.
Even if we assume the blacking process to be similar to electroplating and capable of producing aerosols it must be noted that Nickel Sulphate, in the average plating bath, is generally maintained in the concentration range of 150- 300 g/l. Blackfast 181, as supplied, contains less than 50g/l and diluted to working strength (25%) less than 11g/l.
The data available on groups of nickel species in workrooms indicated that nickel species are not uniform among electroplating shops. Nevertheless an estimate was made for a typical and a worst-case nickel speciation, but the validity of the estimated data remains unknown. TERA (1999) reviewed the toxicology of soluble nickel salts and on basis of the data on occupational exposure provided by NIPERA (1996) it was concluded that the median exposure by inhalation of soluble nickel salts was about 20 µg/m3 in electroplating operations.
We should therefore be able to conclude that Blackfast 181, if capable of producing aerosols, would produce, as an absolute maximum, half the amount of inhalable nickel that a plating bath would i.e. 10µg/m3. This equates to 0.01mg/m3.