Nickel, chromium and cobalt in consumer products: revisiting safe levels in the new millennium

Abstract

The transition metals nickel (Ni), chromium (Cr) and cobalt (Co) are common causes of allergic contact dermatitis (ACD). Given the high frequency with which these allergens can be associated with hand eczema in those responsible for domestic work, it has been suggested that contamination of household consumer products with these metals may be of relevance to the causation/chronicity of hand dermatitis. Dose-response studies using 48 h occlusive patch test conditions in sensitized individuals show that !90% of sensitized patients fail to react below 1 p.p.m., even on irritated skin. Assessment under more realistic exposure conditions has shown that in the presence of irritants and/ or following repeated exposures, such individuals rarely react to levels below 10 p.p.m. On the basis of this information, it was recommended a decade ago that household (and other consumer) products should not contain more than 5 p.p.m. of each of Ni, Cr or Co and that, for an even greater degree of protection, the ultimate target level should be 1 p.p.m. The data generated since the original recommendations were made serve to reinforce the validity of these recommendations. Indeed, it is our view that typically the level of each of these transition metals should not normally exceed 1 p.p.m. Then, where consumer products meet this guideline fully, modern quantitative risk assessment shows clearly that elicitation of ACD is highly improbable, and the chance of the induction of sensitization is even lower. Some 10 years ago, the possibility that traces of the allergenic transition metals, nickel (Ni), chromium (Cr) and cobalt (Co), present as contaminants in household products might give rise to allergic contact dermatitis (ACD) was raised (1, 2) and then extensively reviewed (3). At that time, it was concluded that the risk of the induction of sensitization was negligible and the risk of elicitation in presensitized individuals was acceptably low, as long as the level of contamination was kept to very low levels: 'It is recommended that, for consumer products, current good practice which ensures Ni, Co and Cr contamination is less than 5 p.p.m. of each metal is an acceptable standard. To minimize the risk for very sensitive individuals (4), and when and where standardized analytical techniques permit, it is recommended that the ultimate target should be not more than 1 p.p.m. of each metal in consumer products.'Since that publication, several new pieces of information have become available. Firstly, an interlaboratory study in Italy of housewives' eczema showed no relationship of this disease to transition metal allergy (5, 6). In addition, new dose-response data which aid our understanding of elicitation thresholds in sensitized individuals have been published and have further information on the levels of product contamination with additional commentary on the possibility that trace levels of Ni, Cr and Co might play a role in ACD (and in particular in the chronicity of some hand eczemas) has been presented. Finally, now there are sop...

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A Critical Role for Thymic Stromal Lymphopoietin in Nickel-Induced Allergy in Mice

“…Therefore, we attempted to establish a model for more severe Ni allergy using adjuvants, because some patients present with erosion and infection of lesions in the skin and oral mucosa, suggesting that the development of metal allergy may be exacerbated by other factors, such as bacterial infection. Although Ni is the most frequent cause of metal allergy (2,5), the precise mechanisms underlying Ni-specific reactions remain unknown. In a previous report (20) using an Ni allergy model, we demonstrated that the activation of DCs through p38MAPK/MKK6 is involved in the induction of Ni allergy.…”

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