title: Nickel skin levels in different occupations and an estimate of the threshold for reacting to a single open application of nickel in nickel-allergic subjects.
abstract: BACKGROUND
  Nickel is a frequent allergen throughout the world. However, the extent to which nickel is relevant as an occupational contact allergen as opposed to being simply a reflection of jewellery exposure has been unclear. Some thresholds for cutaneous nickel exposure to induce a dermatitis reaction in nickel-allergic individuals have been defined. Over recent years it has become possible to measure accurately the quantity of nickel on the skin of individuals in a number of occupations.
  
  
  OBJECTIVE
  To measure the quantities of nickel on the skin of the fingers in workers employed in occupations for which nickel has been suspected as a contact allergen. To define the threshold for a dermatitis reaction after the single application of a quantity of nickel to the skin of nickel-allergic individuals when read at 2days.
  
  
  METHODS
  We employed the 'finger immersion' technique for sample collection and induction coupled plasma mass spectrometry for the nickel measurement. Nickel platers, cashiers, sales assistants, caterers, healthcare assistants, office workers, dental nurses and hairdressers were studied (five in each group except for seven cashiers). A correction was made for the fact that the finger immersion method underestimates the amount of nickel on the fingertip. The threshold for reactivity to a single application of nickel was studied by the application of various concentrations of nickel (μgcm(-2) ) [0·05 (two subjects), 0·5 (two subjects), 2·5 (three subjects), 5·0 (21 subjects), 15 (19 subjects), 30 (19 subjects) and 45 (18 subjects)] in 21 subjects overall using Finn chambers on forearm skin. The reading was made at 2days and reactions were graded using the International Contact Dermatitis Research Group classification.
  
  
  RESULTS
  Nickel levels on the fingers of platers, cashiers, sales assistants, caterers, and even office staff, were at or above the 0·035μgcm(-2) level at which 22% of nickel-allergic subjects will react (after applying a correction). The single open application of nickel study demonstrated a dose-response relationship, with no subjects reacting to ≤ 2·5μgcm(-2) , but increasing numbers reacting at the higher concentrations as follows: six of 21 (28%) at 5·0μgcm(-2) , six of 19 (31%) at 15μgcm(-2) , seven of 19 (37%) at 30μgcm(-2) and 11 of 18 (61%) at 45μgcm(-2) .
  
  
  CONCLUSIONS
  This study confirms that nickel levels on the skin in coin handling occupations and some others are sufficient to induce an allergic contact dermatitis in some nickel-allergic subjects. A single application of 5μgcm(-2) when read at 2days induced a dermatitis reaction in six of 21 nickel-allergic subjects.
authors.affiliation: Department of Dermatology, Royal Hallamshire Hospital, Sheffield S10 2JF, U.K. Department of Analytical Chemistry, University of Sheffield, Sheffield S3 7HF, UK. david.gawkrodger@sth.nhs.uk
authors.forename: D J
authors.initials: DJ
authors.lastname: Gawkrodger
authors.forename: C W
authors.initials: CW
authors.lastname: McLeod
authors.forename: K
authors.initials: K
authors.lastname: Dobson
mesh_terms: D017449:Dermatitis, Allergic Contact / Q000209:etiology*; D009783:Dermatitis, Occupational / Q000209:etiology*; D004305:Dose-Response Relationship, Drug; D005385:Fingers; D006801:Humans; D013058:Mass Spectrometry; D009532:Nickel / Q000633:toxicity*; D009717:Numismatics; D016273:Occupational Exposure / Q000009:adverse effects; D010328:Patch Tests / Q000379:methods; D012016:Reference Values; D012867:Skin / Q000737:chemistry*
chemical_list: D009532:Nickel