This means that some parts of their lung tissue are permanently affected reducing respiration capacity. Unfortunately, this process is irreversible. A compilation of studies from Australia, Finland, Denmark, Sweden, Scotland, the USA and Canada indicate very high levels of occupational respiratory problems in farm workers. It is even worse in pig barns. It is characterized by increased coughing and phegm production.
Cells lining the airways produce excess mucus to intercept and expel dust.
Bronchitis symptoms usually occur in workers exposed for 2 or more hours a day to dusty barns. When symptoms last at least three months per year, for at least three years. Some producers suffer from airway obstruction, which may or may not accompany chronic bronchitis. The overproduction of mucus in the airways tends to reduce the airflow passage and contribute to shortness of breath. However, most farmers develop these symptoms without having any pre-existing allergies.