Introduction
Silo-filler's illness is a term used to describe the harm caused by silo gas exposure. Inhaling even a small amount can cause significant, permanent, or deadly lung harm. Nitrogen dioxide reacts with water in the lungs to produce highly corrosive nitric acid. High nitrogen dioxide concentrations might render a person unconscious for 2 to 3 minutes.
Inhaling oxides of nitrogen (NOx) can result in sudden mortality, pulmonary edema, and bronchiolitis obliterans. Major exposure can also cause methemoglobinemia. Nitrogen dioxide attaches to hemoglobin with high affinity, producing nitrosyl hemoglobin that is easily oxidized to methemoglobin. Methemoglobin causes a leftward shift in the oxygen dissociation curve, impairing oxygen delivery and exacerbating the already present hypoxia.
What Is Silo-Filler's Disease?
Silo gas (a mixture of nitrogen dioxide (NO2) and carbon dioxide (CO2)) occurs after a few hours to three weeks of adding fresh plant material to a silo. Carbon dioxide (CO2) is also produced throughout the process, but usually not in lethal quantities. Carbon dioxide is a higher problem in a controlled environment (sealed silos).
This is a concern in traditional, non-airtight silos. However, it is also produced in horizontal silos and silage bags. NO2 is created from nitrates in maize or hay, which are transformed into nitrites and oxygen by anaerobic fermentation, resulting in NO2. The fumes range from yellow to reddish brown, and the NO2 odor resembles household bleach. Gas forms within a few hours of the silo being filled reaches a peak 1 to 5 days later, and can produce dangerous levels for 2 to 6 weeks.
How Is Silo Filler's Disease Diagnosed?
Patients in the acute phases of silo filler's disease will exhibit moderate to severe respiratory distress. Systemic hypotension, severe hemoconcentration, methemoglobinemia, and severe metabolic acidosis may all be present. Leukocytosis is typical. Pulmonary function tests indicate decreased vital capacity, increased airway resistance, poor gas transfer, and hypoxemia. Because the initial stage of illness may be modest, individuals may seek medical attention for the first time after a recurrence, which can occur two to six weeks after NOx exposure.
Cough, tachypnea, dyspnea, a high temperature, tachycardia, cyanosis, and other respiratory symptoms are currently caused by bronchiolitis obliterans. Small, distinct nodules, with or without confluence, will be visible on the chest radiograph. Silo filler's disease can be confused with a variety of disorders caused by moldy hay or grain, such as hypersensitivity pneumonitis or toxic organic dust syndrome (TODS). When working around a silo, mold exposure is most common when uncapping the silo and removing moldy silage from the top silo layers after the harvest season. Thus, the timing differs from that of the silo filler's sickness.
A complete medical and occupational history is essential for accurate diagnosis. In addition to remembering exposure to a recently filled silo, which is most prevalent in late summer or the beginning of fall, a patient may recollect seeing NOx near the silo or having the previously stated transitory symptoms. Because exposure to silo gas could have happened hours to weeks before the start of severe respiratory symptoms, the patient might not associate the symptoms with silo gas. Prompt diagnosis and treatment of individuals with acute symptoms are critical to preventing death and, in the case of an initial illness, reducing the likelihood of relapse.
How Is Silo Filler's Disease Treated?
Any symptomatic patient who has been exposed to NOx must be cautiously examined by a physician for 48 hours due to the risk of abrupt pulmonary edema. These patients are usually hospitalized. In some circumstances, patients may be able to stay at home, but they should be advised to contact their doctor promptly if they experience respiratory distress.
To reduce the risk of bronchiolitis obliterans, people with pulmonary edema or respiratory discomfort should be put on steroids for at least eight weeks. People experiencing bronchiolitis obliterans for the first time should also be treated with steroids. Patients may need intense supportive care, such as oxygen, bronchodilators, or ventilatory assistance.
Antibiotics may be required for a subsequent respiratory infection. NOx reactions vary depending on the concentration of gas inhaled and the duration of exposure. Ocular irritation and a temporary upper respiratory tract syndrome apparent as cough, potentially accompanied by dyspnea, weariness, nausea, cyanosis, and vertigo, are caused by relatively mild NOx exposure.
Symptoms may be sufficiently severe to prompt employees to leave the silo. When reactions to NOx are mild, workers may remain in the silo, increasing the likelihood of a severe reaction. Although symptoms may remain for one to two weeks, chest radiographs, pulmonary function tests, and blood gases are normal, indicating complete recovery.
How Is Silo Filler's Disease Prevented?
Silo filler's illness is an avoidable occupational hazard that correct work procedures can avoid. Farmers must properly comprehend the risks connected with newly filled silos. After filling out the silo, no one should enter it for at least two weeks. To prevent NOx from pouring down the chute, keep all silo doors locked during and after filling. The door that connects the silo room and the barn should remain closed.
Animals and kids should be maintained away from the silo and adjacent feed room throughout the filling process and for two weeks after that. A few days before entering the silo for the first time, use a rope to pull the filling aperture open from the ground rather than the chute. The blower should be turned on for at least half an hour before entering, and other forms of ventilation should be used to their full potential. Detector tubes that measure NO2 concentrations are relatively priced and, when used correctly, reliable.
Conclusion
Silo filler's disease is a dangerous respiratory disorder induced by inhaling nitrogen dioxide from freshly filled silos. Acute symptoms can be moderate or severe, with the possibility of developing chronic pulmonary illness in some cases. Prednisone is an effective therapy, and preventative strategies include good ventilation and awareness. Despite long-standing awareness of the disease, ongoing efforts are required to safeguard farm workers from this avoidable condition.
