title: Construction of job-exposure matrices for the Nordic Occupational Cancer Study (NOCCA).
abstract: BACKGROUND
  The Nordic Occupational Cancer study (NOCCA) is a cohort study based on employed populations in one or more censuses in Denmark, Finland, Iceland, Norway and Sweden. The large size of the cohort allows us to study rare cancers and to identify even small risks by occupation and by specific occupational exposures. This paper describes principles and experiences of the construction of job-exposure matrices (JEMs), an instrument to transform the history of occupational titles into quantitative estimates of exposure to potential carcinogenic substances.
  
  
  METHODS
  For each Nordic country, a national JEM was constructed by a team of experts on the basis of the Finnish matrix (FINJEM) that has been used in similar national studies since the mid-1990s.
  
  
  RESULTS
  The structure of the Nordic JEMs is three-dimensional (over 300 occupations, over 20 agents, 4 periods covering 1945-1994). Exposure is characterised by estimates of the prevalence and level of exposure. Important differences between the Nordic countries were observed for several exposures.
  
  
  CONCLUSIONS
  The selection of priority agent-occupation combinations and the adoption of general principles in the beginning of the work were necessary because of the high number of estimates to be evaluated (over 50 000/country). The selective modification of an existing JEM for use in other countries was a feasible, albeit challenging task, because exposure data and information about the use of chemicals in the past was scanty. As compared to the use of FINJEM for all Nordic countries, the modification process will probably increase the validity of dose-response and risk estimates of occupational cancer which is to be expected soon as the main outcome of the NOCCA project.
authors.affiliation: Finnish Institute of Occupational Health, Topeliuksenkatu 41aA, 00250 Helsinki, Finland. Timo.Kauppinen@ttl.fi
authors.forename: Timo
authors.initials: T
authors.lastname: Kauppinen
authors.forename: Pirjo
authors.initials: P
authors.lastname: Heikkilä
authors.forename: Nils
authors.initials: N
authors.lastname: Plato
authors.forename: Torill
authors.initials: T
authors.lastname: Woldbaek
authors.forename: Kaare
authors.initials: K
authors.lastname: Lenvik
authors.forename: Johnni
authors.initials: J
authors.lastname: Hansen
authors.forename: Vidir
authors.initials: V
authors.lastname: Kristjansson
authors.forename: Eero
authors.initials: E
authors.lastname: Pukkala
mesh_terms: D016021:Epidemiologic Studies; D006801:Humans; D009369:Neoplasms / Q000453:epidemiology*; D009784:Occupational Diseases / Q000453:epidemiology*; D016273:Occupational Exposure / Q000032:analysis*; D011379:Prognosis; D012537:Scandinavian and Nordic Countries / Q000453:epidemiology