Air Quality, Health Effects and Management of Ammonia Emissions from Fertilizers

Emissions of ammonia have been demonstrated to play a role in the formation of airborne fine particulate matter, by reacting with gaseous emissions of sulphur dioxide and oxides of nitrogen. Agriculture emits ammonia to the atmosphere, and atmospheric processes can transport the particulate form of ammonium long distances. Fertilizer use-related emissions have been estimated to comprise 10–35 % of all agricultural emissions. The potential contributions of ammonia emissions from agriculture to the formation of particulate matter, and to its harmfulness, are questions being addressed by current research. Recent expert reviews have concluded that exposure to airborne particulate matter air pollution contributes to human mortality. Epidemiological evidence suggests that exposures as short as a few hours to a few weeks are associated with small but significant increases in cardiovascular disease-related mortality, and that the size of the effect increases with longer-term exposures. Plausible biological mechanisms for inhaled particulate matter triggering physiological responses in the cardiovascular system have been described, though much remains uncertain. The specific constituents of particulate matter causing the responses have not been identified with certainty, and thus a direct link between emissions from fertilizer use and human health risks has not been demonstrated. Ammonia emissions from fertilizer can be controlled through the choice of source, rate, timing and placement. Key practices already in use to minimize emissions include placement in soil of any fertilizer with potential to release ammonia, and, for urea specifically, use of urease inhibitors, coatings or formulations to slow release. Even though the reduction in risk to human health is not currently well-known enough to be predictable, the evidence is sufficient to warrant recommendations for continued increase in the use of practices designed to reduce ammonia emissions, and for increased research efforts to develop such practices further.