Odour & Ammonia (2)

The ammonia gas emitted from hen sheds will deposit locally, within a few metres of the sheds. This is often referred to as "dry deposition". However, it can also rise in the atmosphere where it may dissolve in rain drops and fall to earth (described as "wet deposition") or it can combine with acid pollutants in the atmosphere, such as nitric and sulphuric acid, to form "ammonium" as fine particulate matter ("aerosol form"). (4) In its wet and aerosol forms the ammonia can be transported much greater distances. Research in Wales has shown (5) that over a 12 month period significant quantities of ammonia were detected 2.8 km upwind from an intensive poultry unit, emphasising the mobility of ammonia in these forms.

This redistribution of the ammonia provides another source of nitrogen to the ecosystem. These levels are comparatively small but are extremely damaging to ecosystems which have developed in areas where there is only a low concentration of nutrients available, such as mountainous regions, moorland, bogs and the ground flora in woodlands (7). The loss of these ecosystems will impact on the animals and birds that feed on them, thereby reducing biodiversity.

The aerosol form is harmful to humans because the particles are small enough (less than 2.5 microns) to penetrate deep into the lungs. Particulate matter has particularly negative impacts on cardiovascular and respiratory health, contributing to various chronic conditions such as heart attacks, cerebrovascular disease, chronic obstructive pulmonary disease (COPD), asthma and lung cancer (4,6).