An epidemiological survey of respiratory symptoms caused by inhaled organic farm dust was performed in 1982. An extensive questionnaire was mailed to farmers on 3,197 farms in the middle part of Sweden. 3,370 farmers from 72% of the farms replied. The inclusion criteria-age 15-65 and working more than 30 hourslweek with farming or farming forestry-were met by 2,174. A stratified sample of farmers were asked to attend an oral interview, which was conducted by physicians with special training in farmer's health problems; 389 farmers completed the interviews (77 % of those invited). On the same occasion, simple spirometry and a skin prick test were performed and blood samples were taken for determination of serum IgE and precipitating antibodies in serum using the double diffusion method.
Dust samples were collected from the breathing zone during normal handling of grain, hay, straw, or wood chips on 40 farms. The total count of microorganisms, the size distribution, and the number of colony-forming units on different culture media incubated at different temperatures were measured, and the main microorganisms were identified.
The design focused on effects caused by the inhalation of mold dust. Obstructive symptoms following inhalation of other organic dusts in the farm environment, such as from nonmoldy hay or grain were, however, also recorded.
It was found that 2% of the farmers had asthma, and an additional 4% had experienced symptoms of airway obstruction related to the inhalation of dust from the farm. A further 4% had experienced wheezing in the chest, but not with a clear association with the inhalation of dust from the work environment. Those with obstructive symptoms had, on average, a decreased lung function, increased serum IgE levels, and a higher prevalence of positive skin prick tests.
Six percent of the famers had experienced febrile reactions to the inhalation of mold dust according to the diagnosis made at the interview. The majority of farmers with febrile symptoms had had more than one attack. The attack usually lasted only a Lung Physiology Section, National Board of Occupational Safety and Health, Solna, Sweden (P.M.).