5.2 Exposure Assessment5.2.1 Humans

5.2 Exposure Assessment
5.2.1 Humans
In considering the potential for inhalation exposure for humans, background levels of ammonia gas in community ambient air tend to be low. Greater variability in ambient levels of ammonia gas are expected near non-point and point sources.
5.2.2 Vegetation
Close to sources, vegetation exposures to NH3 and NH4+ (NHy) can be expected to occur. NHy is deposited rapidly within the first 4 to 5 km from sources. While vegetation exposures to NHy can be expected at greater distances from sources, they are of considerable less importance than that occurring closer to the sources.
5.2.3 Materials
The implication of material effects from exposure to ammonia is difficult to separate from the effect of other air pollutants. However in urban environments with important industrial point sources of ammonia, the role of multi-pollutant – including ammonia – exposures may be an issue where material damage is occurring.
5.3
Toxicity Assessment
5.3.1
Human Health
5.3.1.1
Potential Health Effects of Exposure
Two different types of potential health effects are relevant for ammonia: acute non-cancer effects that result from short-term exposure; and chronic non-cancer effects that result from long-term (chronic) exposures. The specific conditions of ammonia exposure to animals and/or man corresponding to these types of effects vary and were further discussed in Section 4.
In general, acute health effects reported in animals following short-term inhalation of ammonia may include oral, nasal and eye irritation; respiratory tract irritation; decreased respiratory rate; increased respiratory depth; reduced body weight; and lethargy. The acute effects of ammonia inhalation by humans are similar to those reported in animal studies and include oral, nasal and eye irritation; respiratory tract irritation; and increased respiratory depth.
The health effects following chronic exposure of animals to ammonia via inhalation may include nasal irritation; inflammatory response in lungs; reduced olfactory acuity; and lethargy. Animal studies have also demonstrated that ammonia exposure reduces immune response and increases susceptibility to bacterial infection of the respiratory tract. Chronic effects reported in humans include reduction in pulmonary function; cough; phlegm; wheeze; and dyspnea.