Inge Brosbøl Iversen

Exposure was assessed from the first registered employment year after 1976, which is the year of first registrations in DOC*X, and until the end of follow-up. We started follow-up in 1994 for those with a first year of employment before 1994. If the first year of employment was 1994 or later, follow-up started the year following the first year of employment, as we had no information on the month or day of employment. For the same reason, we also lagged all independent variables by 1 year.

We studied the total Danish working population, which allowed us to study these relatively rare diseases. Some patients with minor symptoms may not be referred to hospitals, but we do not expect the likelihood of referral to be associated with exposure status as healthcare in Denmark is universal with no user payment. All diagnoses were retrieved from the National Patient Register, which is used extensively for epidemiological research.

Discussion In the present study, we observed an increasing risk of HP, other ILDs and all ILDs with increasing cumulative exposure to organic dust and endotoxin, but not to wood dust. Risk of all three outcomes also increased with increasing recent organic dust and endotoxin exposure. No increased risk was observed for wood dust exposure.