Indoor Air Quality in Pig Buildings: Why is it Important and How is it Managed?

 Air quality is an assessment of how many contaminants (particulates, vapours) are present in addition of the various gases constituting normal, clean air. The more contaminants present in the air, the lower the air quality is. The main contaminants in swine buildings are dust, hydrogen sulphide, ammonia, carbon dioxide, various micro-organisms and other gases. The air of swine confinement buildings is highly contaminated with bacteria, yeast and moulds at a level up to 1,200 times higher than so called "normal air".

For each contaminant, there are some exposure limits to be maintained in the barn to ensure worker health and safety. Carbon dioxide concentration may exceed 4,000 ppm under winter conditions but will normally be lower than 1,000 ppm in summer time. The same trend can be observed with ammonia. Its concentration can be between 20 and 30 ppm under winter conditions, but it is much lower during the summer. Under normal barn management when the pits are emptied frequently, the concentration of hydrogen sulphide, methane and other gases will be very low from a human safety perspective. Hydrogen sulphide is mainly released when pig manure that has been stored under anaerobic conditions and is agitated in any way. A proper personal respirator should be worn whenever someone needs to enter an enclosed area where hydrogen sulphide or other gases may have accumulated. Methane will be produced when liquid manure kept in storage for a long time is maintained in anaerobic conditions.

Generally speaking, dust particles having an aerodynamic diameter larger than 0.5 micrometers (1 micrometer is 1 million times smaller than a meter) are defined as inhalable dust because they can be inhaled by the upper respiratory tract of a person. A large portion of those particles will stay trapped in the nose or the throat. Respirable dust particles that have an aerodynamic diameter between 0.5 and 5.0 micrometers will travel deeper into a person's respiratory system. Being so small, those particles can transport micro-organisms or gas molecules very deep into the lungs and have a combined impact as lungs are exposed to more than one contaminant type. Therefore, reducing large dust particles in the air will not always reduce the amount of airborne small particles. Wearing a two-strap disposable mask is the best way of protecting yourself against pig dust and the long-term effect it might have on your lung functions. In the case where a pig producer is willing to invest some dollars to improve air quality in the barn, the oil sprinkling technique is certainly the most promising solution and is worth considering. See your physician on a regular basis to verify your personal capabilities of dealing with a barn environment exposure and keep him/her informed of your working situation.

Relative humidity, although not a contaminant in itself, is a very easily measured component in the air that can be used to determine if there are other potential contaminants.

Overall, more research is needed to investigate the impact of the contaminants present in pig barns. Exposure limits have been defined for single contaminants and very little information is available on the synergy of those contaminants together.