![]() Patients in the acute stages of silo filler's disease will present with moderate to severe respiratory distress. The severity of the hazard rests partially in the high case fatality rate: 29 percent of cases cited in medical literature have been fatal. Other statistics on the frequency of agricultural NOx exposure are not available, but a number of deaths have been documented through the years. ![]() An unpublished survey in the late 1960's revealed that 4.2 percent of Wisconsin farm operators had developed symptoms of NOx inhalation when working in or near freshly filled silos. Lthough probably not common, the true scope of exposure to NOx is thought to be underestimated. The term, "silo filler’s disease," was established in 1956. This occurred when three men fell into a silo and were asphyxiated by a gas that was unknown at that time. The first recorded incidence of a death from SFD was in 1914. When farm workers enter the silo or are near its open hatches during the first 10 days after filling (without proper precautions), they may experience various degrees of silo filler’s disease. Hours after the organic material is stored, toxic and lethal levels of nitrogen dioxide, which is heavier than air, develop on top of the silage. It forms rapidly in farm silos that are filled with fresh organic material (e.g., corn, grains). Nitrogen dioxide is a reddish-brown gas that emits an odor similar to that of household bleach. Most symptomatic exposures are mild and self-limiting however, some cause sudden death from asphyxiation, pulmonary edema, or weeks later, bronchiolitis obliterans. More severe exposure can result in laryngeal spasm, bronchiolar spasm, reflex respiratory arrest, or asphyxia, leading to death. With an increase in concentration and duration, the exposed person additionally may experience cyanosis, vomiting, vertigo, and a loss of consciousness. Low concentrations of nitrogen dioxide cause cough, dyspnea, fatigue, and upper airway and ocular irritation. Methemoglobin results in a leftward shift of the oxygen disassociation curve, which impairs the oxygen delivery and compounds the already present hypoxia. Nitrogen dioxide binds to hemoglobin with great affinity, forming nitrosyl hemoglobin, which is readily oxidized to methemoglobin. Significant exposure can also result in methemoglobinemia. Inhalation of oxides of nitrogen (NOx) can cause sudden death, pulmonary edema, and/or bronchiolitis obliterans. ![]() Silo filler's disease (SFD) is an occupational pulmonary disease resulting from exposure to oxides of nitrogen. Report to the IDPH Division of Environmental Health:Ģ4-hour Disease Reporting Hotline: (For use outside of EH office hours) 80
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