text: One major difficulty surely is the**reliable description of exposures at work**. Workers might have had 
  **several occupations during their working life, or changed work tasks in the same occupation**due 
  to organisational and technological developments, and they might also have changed the specialisation 
  in this occupation; also the**level of prevention measures differs**between sectors and countries. Of 
  course, all this influences the exposure patterns. 
  
  **EU-OSHA**applied in its study on ‘Costs and benefits’ estimates, attributable fractions (AF) based on the 
  evaluation of literature and statistics. The AF vary between 1% for all respiratory diseases, 3.2% for 
  neoplasm and 12.4% for circulatory diseases up to more than 90% for mesothelioma and 100% for 
  pneumoconiosis.212 For mental diseases the estimated AF is 17.4 % for males and 20.7 for females.213 
  
  There are very clear connections between specific lung diseases (e.g. pneumoconiosis) and work 
  because**such exposures are often restricted to workplaces**, as outside work there is practically no 
  exposure; many of these diseases are recognised as occupational diseases. Much less clear are the 
  attributions of work to cardiovascular, mental, other respiratory diseases like asthma or COPD, and 
  digestive diseases. 