Silo-Filler's Disease: One Health System's Experience and an Update of the Literature.

Silo-filler's disease, a life-threatening condition from exposure to silage gas in recently filled silos, has been known for over 5 decades now. However, farm workers remain exposed to this preventable condition. We describe the index presentations and subsequent changes among 19 patients managed within our health system over a 61-year period and highlight the need for ongoing education on minimizing exposure to silo gas.

Nitrogen dioxide (silo gas) poisoning in dairy cattle.

Toxic silo gases are a potential danger to livestock housed in close proximity to roughage silos. These gases, such as nitrogen dioxide (NO2), may be produced during the early stages of (maize and grass) silage making. In humans, inhalation of these gases causes a condition known as 'Silo Filler's Disease' (SFD), which is a recognized occupational hazard for workers in upright forage silos in many countries. NO2 accumulates on top of silage, is inhaled by workers, and reacts with water on the airway surfaces to form nitrous acid, which damages the lung and causes pulmonary oedema, bronchiolitis, and death in severe cases. On a dairy farm, a cloud of reddish-brown NO2 gas (which is heavier than air) was noticed to escape from underneath the plastic sheet of a horizontal maize bunker and to enter a cubicle house for dairy cows 1 day after ensiling. Eleven cows became dyspnoeic, 3 of which subsequently died. A combination of weather conditions, an insufficient sand load on the maize bunker, the utilization of a lactobacillus starter culture, and the close proximity of the silo to the cubicle house may have caused the incident.

An assessment of gases in oxygen-deficient hay silos and the effects of forced ventilation.

Many modern tower silos used in the agricultural industry for hay and grain storage are oxygen-limiting by design. Forced-air ventilation using a forage blower is a method commonly used to decrease concentrations of toxic and asphyxiant gases and to increase the O2 content within a silo headspace prior to worker entry. This article describes the methods used to measure gas concentrations and the results obtained from a pilot study by the Washington Fatality Assessment and Control Evaluation (FACE) program of two oxygen-limiting forage tower silos in eastern Washington State. The silos were monitored for oxygen (O2), nitrogen dioxide (NO2), and carbon dioxide (CO2). Measured O2 concentrations were low in all areas of the headspaces monitored for both silos. After beginning forced-air ventilation, O2 concentrations within the silo headspace returned to ambient levels within 8 to 20 min. Nitrogen dioxide levels exceeded the Washington Industrial Safety and Health Act (WISHA) short-term exposure limit (STEL) in the silo that was filled six days earlier (silo 2), but not in the silo that was filled four days earlier (silo 1). The NO2 concentration in silo 2 decreased to below the WISHA STEL within 15 min of starting ventilation but began to rise shortly after ventilation was stopped. Carbon dioxide, which was only measured in silo 1, was detected at 2% within the headspace of this silo. The carbon dioxide concentration decreased to <1% within 3 min of starting ventilation.

[Accidental poisoning with silo gas]. / Przypadkowe zatrucie gazem silosowym.

Eight cases of poisoning in workers cleaning silo are presented. Silo gas, produced during fermentation of vegetable material, contains very toxic nitrogen oxides. In this group three workers died within silo, four patients were hospitalized (one of them with acute toxic pulmonary oedema, two with sings of pneumonia, one had only transient decrease of consciousness) and recovered without detectable sequelae. One patient, in general good condition, refused hospitalization and recovered.

Lung (agricultural/rural).

Industrialization of farming, animal raising, and forestry has added chemical and mechanical hazards that need to be recognized and prevented. Lung disease among farmworkers can result from a wide variety of hazardous exposures, which include organic dusts, allergens, chemicals, toxic gases, and infectious agents. In addition to nonspecific symptoms of mucous membrane irritation, farmworkers can experience occupational asthma or bronchitis, organic dust toxic syndrome, hypersensitivity pneumonitis, silo filler's disease (toxic hemorrhagic pulmonary edema), and neuromuscular respiratory failure. At risk are farmworkers and those involved in the processing, stocking, transportation, handling, and inspection of unprocessed agricultural, animal, and forestry products; veterinarians; gardeners; game, river, and forest keepers; persons involved in building, supplying, or servicing farm operations; and residents of rural communities. Worker education on the risks of environmental exposures, adherence to safety regulations, and increased knowledge of the cause and prevention of environmental diseases will reduce their prevalence and their adverse human and animal health and socioeconomic effects.

Silo filler's disease in New York State.

Twenty new cases of Silo filler's disease (SFD) have been collected, documenting the incidence and clinical features of exposure to nitrogen oxides present in freshly filled silos. Cases of SFD were identified using a statewide computerized discharge diagnosis system. Fifteen of these were identified in the index period, allowing us to calculate an approximate annual incidence of 5.0 cases/100,000 silo-associated farm workers/yr in New York State. All cases occurred during harvest periods, with 80% in September and October. Corn silage was the gas source in 18 (90%). All cases involved young white men (mean age, 31.5 yr). The most common presenting feature was dyspnea. All victims entered a silo during the peak danger period, and only one used recommended ventilation techniques. Four cases ended in death (20% mortality). Silo filler's disease, although rare, is a potentially devastating disease involving otherwise young, healthy farm workers. It is readily prevented.

[Silo filler's syndrome]. / Siloentladersyndrom.

In 1975 an acute febrile bronchopulmonary illness after massive inhalation of fungal spores in silos was described as "pulmonary mycotoxicosis". Subsequently the disorder was referred to as "silo unloader's syndrome" or as a special form of "organic dust toxic syndrome" (ODTS). In this article the three cases of silo unloader's syndrome recognized by the Swiss National Accident Insurance Company (SUVA) between 1978 and 1989 as being an occupational disease are described. Two of the three patients with ODTS were wrongly diagnosed as suffering from allergic alveolitis and a change of occupation was proposed. Therefore, it is important to recognize ODTS in order to avoid unnecessary treatment and a change of occupation. ODTS can be prevented by technical measures such as prevention of mould formation and, in the case of exposure to fungal spores, use of an adequate breathing mask or a powered dust respirator helmet.

Agricultural disorders of the lung.

Agricultural workers are at risk for developing many respiratory tract disorders. Crop production disorders include chronic bronchitis, asthma, organic dust toxicity syndrome, chemical poisoning, farmer lung, and silo-filler disease. Livestock production disorders include toxic manure poisoning (dung lung) and several zoonoses. Radiographic manifestations can be classified into three patterns: (a) normal findings, characteristic of chronic bronchitis, asthma, or organic dust toxicity syndrome; (b) acute diffuse interstitial or alveolar pattern, characteristic of farmer lung, silo-filler disease, dung lung, and chemical poisoning; and (c) chronic interstitial pattern in the upper lobes (farmer lung) or lower lobes (silo-filler disease, paraquat poisoning). Differential diagnosis is aided by knowledge that most of these disorders have a seasonal presentation. Zoonoses generally exhibit focal areas of consolidation in the lung: The type of splenic calcification, presence of mediastinal or hilar adenopathy, and development of bronchiectasis are additional findings useful in differentiating these rare infections.

[Acute dyspnea, cough, headache]. / Akute Dyspnoe, Husten, Kopfschmerzen.

Six hours after work in an empty, non-ventilated silo a 27-year-old Yugoslav worker suffered acutely from cough, dyspnea and general weakness. He was admitted to the hospital with severe partial respiratory insufficiency, and after emergency intubation artificial respiration had to be installed. X-ray showed a severe symmetrical alveolo-interstitial opacity. The heart configuration was normal. History revealed that the neighbouring silo had been filled with green corn the day before. Both silos were connected by a common drain-wall. Furthermore, a yellowish discolouration of the new paint in the empty silo was noted. Based on these facts silo-filler's disease was diagnosed. The patient recovered rapidly under high doses of steroids. Lung function was normalized within nine days, and the patient was released from the hospital. Steroid therapy was continued for six weeks.

[Storage mite allergy. Routine tests]. / Formiddallergi. Rutinetesting.

Storage mites are sources of allergy among farmers and silo workers. Among 114 patients with allergic rhinitis we found four with a positive prick test to storage mites. This is not sufficient reason to include storage mites in a standard allergy prick test series.

Bronchoalveolar lavage findings in a patient with the organic dust toxic syndrome.

A previously healthy student developed the organic dust toxic syndrome after unloading a grain silo for one day. Bronchoalveolar lavage seven days later showed a total cell count six times normal with 70% lymphocytes. This suggests that the previously described acute neutrophil influx into the alveolar spaces in this syndrome is rapidly replaced by a lymphocyte dominated infiltration.