Chest
Volume 117, Issue 5, May 2000, Pages 1488-1495
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Occupational and Environmental Lung Disease
Longitudinal Changes in Bronchial Responsiveness Associated With Swine Confinement Dust Exposure

https://doi.org/10.1378/chest.117.5.1488Get rights and content

Study objectives

Acute exposure to the air in swine confinement units causes bronchial hyperresponsiveness and inflammation of the airways. This study was performed to assess the longitudinal development of bronchial responsiveness in pig farmers and to establish exposure-response relationships.

Methods

A cohort of 171 pig farmers was followed over a 3-year period. Bronchial responsiveness was assessed by a histamine provocation test. Long-term average exposure to inhalable dust and endotoxin was determined by personal monitoring in summer and winter, using data on farm characteristics and activities. Time-weighted average (TWA) personal exposure to ammonia was measured. Data on farm characteristics were gathered in the same period.

Results

Mean increase in responsiveness was 2.52 doubling concentrations of histamine for a 10% decrease in FEV1 and 1.36 doubling concentrations for a 20% decrease in FEV1. Long-term average exposure to dust was 2.63 mg/m3 and to endotoxin was 105 ng/m3. TWA exposure to ammonia was 1.60 mg/m3. After adjusting for age and smoking behavior, long-term average exposure to inhalable dust was associated with increases in bronchial responsiveness expressed as steps for provocative concentration causing 10% fall in FEV1. TWA exposure to ammonia, use of wood shavings as bedding, and automated dry feeding were associated with increases in responsiveness expressed as steps for provocative concentration causing a 20% fall in FEV1.

Conclusions

Exposure to dust and ammonia in pig farms contributes to chronic inflammation of the airways and should be reduced.

Section snippets

Study Population

In 1990, a questionnaire survey was administered to 1,504 pig farmers.14 To be able to study exposure-response relations, a study population was formed with sufficient contrast in respiratory morbidity, and therefore presumably also in exposure. In 1991, 200 randomly selected subjects from among the respondents with one or more chronic respiratory symptoms (chronic cough, chronic phlegm, shortness of breath, ever wheezing, frequent wheezing, chest tightness/asthma) and 199 randomly selected

Personal Characteristics

Mean age of the 171 farmers was 39.6 years at the start of the observation period (Table 1). Mean number of years worked in pig farming was 16.7. There were small differences in age (41.6 vs 37.6) and number of years worked as pig farmer (18.1 vs 15.4) between symptomatic and asymptomatic farmers at the start of the observation period. Five participants were no longer active as pig farmers in 1995; three of them stopped partly because of respiratory problems. Percentage of cigarette smokers was

Discussion

In this 3-year follow-up of 171 pig farmers, we found a sharp increase in bronchial responsiveness. Long-term average exposure to inhalable dust was associated with increases in bronchial responsiveness expressed as concentration steps for PC10. TWA exposure to ammonia, use of wood shavings as bedding, and automated dry feeding were associated with increases in responsiveness expressed as concentration steps for PC20.

Log-transformed exposure with base 2 was used in analysis. This means that the

ACKNOWLEDGMENT

The authors thank Liesbeth Preller, Rudolf Gerrits, Martin van't Hof, Hans Verboom, Irma van de Heuvel, Gerrie Pletting, Ans Janssen, and the cohort members and the lung departments of the Maas and Elkerliek hospitals.

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