16. A proposed Livestock Burden Index (LBI) for airborne pollutants in livestock buildings

The air in livestock operations contains considerable amounts of various airborne gaseous and particulate components. Inhaled airborne pollutants such as ammonia, dust or dust-related endotoxins can promote infectious and non-infectious diseases in the respiratory tract. Control measures to prevent such harmful accumulations are based mainly on recommended threshold limit values (TLVs). Such individually applied TLVs do not consider the interactions of all airborne pollutants on the respiratory tract. This is particularly true when the concentrations of airborne pollutants fall just below the exposure limits. Nevertheless, in such cases synergistic effects can be expected. To compensate for this limitation we propose a Livestock Burden Index (LBI) for airborne pollutants in pig and chicken housing. Published TLVs from behavioural and dose-response relationship studies were combined in a single formula to calculate the LBI, which considers airborne pollutants such as ammonia, inhalable dust, respirable dust and inhalable endotoxins. The calculated index indicates the magnitude of the pollutant burden in the air. The corresponding level of danger is expressed in five subjective descriptors ranging from slight to extreme. To demonstrate the applicability and the practicality of the LBI, it was retrospectively calculated for measured air quality factors in 48 German conventional livestock buildings. The survey shows that there are serious or extreme problems with the indoor air quality in 22% of all pig buildings and in 25% of all chicken buildings with potential detrimental effects on health and welfare. These values were compared with calculated LBI categories based on field data from Australian piggeries. Despite its preliminary model character the proposed LBI offers the possibility of incorporating further parameters or correction factors if the results of field investigations show that this is necessary. Future field investigations must be undertaken to demonstrate the general suitability of the LBI and its validity.