Don’t Let Silo Gas Stop You Dead

By Jane Fyksen
Thursday, September 6, 2007 5:37 PM CDT

Crops Editor

Corn silage is already coming off some fields. Whole-plant moisture is dropping fast. Producers will be filling silo in force. Cheryl Skjolaas, UW-Madison farm safety advocate is issuing warnings about deadly silo gas and grain dusts and respiratory problems. Beware that nitrates could be an issue this year.

Silo gas forms shortly after green plant material is ensiled and starts fermenting. Oxygen combines with nitrates in the plants n which could be high in corn silage this year n and nitric oxide gas is released. This, in turn, combines with oxygen in the air to form nitrogen dioxide. This heavier-than-air toxic gas can seriously injure n or kill n both cattle and people.

Silo gas forms within a few hours of filling silo and for as long as three weeks after fresh plant material is added to conventional silos.

“Dry growing conditions may cause an increase in the nitrates in the plant material,” says Skjolaas. “Weeds and corn are naturally high in nitrates. Nitrate levels in corn are extremely high after a rain, following a dry period.” She reminds that harvesting corn plants high will help decrease the nitrate level.

“Silo-filler’s disease” is the term given to the injury resulting from exposure to silo gas. Inhaling even a small amount can cause serious, often permanent, lung injury. It can also be fatal.

Nitrogen dioxide combines with water in your lungs to form highly corrosive nitric acid. “High concentrations of nitrogen dioxide may make a person helpless in 2 to 3 minutes, “Skjolaas warns.

Symptoms include: Coughing, burning sensation, shortness of breath, chills, fever, headache, nausea or vomiting. “While a person may not immediately experience the symptoms from a mild exposure, in 3 to 30 hours, there is a slow, progressive inflammation of the lungs that results in fluid buildup in the lungs. This can be fatal,” she stresses.

She notes that a “unique characteristic” of this disease is that there may be a relapse in 2 to 6 weeks after the original episode. This relapse may be milder or more severe than the first.

Stay out of the silo for at least three weeks after filling. Be alert for bleach-like odor and/or yellowish-brown gas in or near the silo. Ventilate the silo room adequately for three weeks after filling by keeping windows and doors open. Keep the door from the silo room to the barn closed to prevent silo gas from reaching your cattle.

If you must enter the silo, to set up a silo unloader, for instance, do so immediately after the last load is in, she advises. “Do no wait several hours or overnight,” she adds. Also run the blower 15 to 20 minutes before entering and keep it running while you’re inside.

Keep a door open down to the silage surface and have someone keep in contact with you from the outside. If you experience throat irritation or coughing in the silo, get out immediately to fresh air. See your doctor immediately after exposure, because, as noted, symptoms often worsen.

Chronic respiratory problems preventable

“Grain dust” is nasty stuff n a mixture of particles of grain, soil, plant material, fungi, bacteria, residues of ag chemicals and the “excreta” of insects, rodents and birds. It’s not something you want to breathe. Preventing respiratory problems is as simple as slipping on a dust mask.

Skjolaas reminds growers to wear one especially this time of year when they’re cleaning out their bins in preparation for the ’07 crops. (Spoiled grain is especially contaminated with dust and bacteria.)

Dusts can affect you in a variety of ways and can also cause gastrointestinal problems, skin rashes and eye irritations. “Individuals may react quite differently to the same dust,” says Skjolaas. “Each person’s work history, health status and smoking history is unique. Thus, some people may be quite sensitive to the dust, while others may be able to withstand several exposures prior to becoming sensitized.” That doesn’t mean, though, that you should work unprotected in dusty areas until problems develop.

Skjolaas highlights the various respiratory problems caused by grain dust:

- Inflammation of air passages (upper airways or acute bronchitis) - Symptoms include stuffy nose, runny nose, sore throat, cough, spitting up phlegm and labored breathing. “These common reactions are bothersome but cause no permanent damage,” she notes.

- Asthma (often called “grain asthma” or “barn allergy”) n Symptoms include wheezing, labored breathing and cough. Asthma can be an immediate response to grain dust or may be delayed for several hours or may recur successive nights following exposure.

- Chronic obstructive pulmonary disease (chronic bronchitis or airway obstruction) n Symptoms include recurring cough, phlegm production for two or more years, labored breathing and wheezing. Prolonged exposure to grain dust can lead to permanent lung damage. Cigarette smokers experience these same symptoms, and smokers who handle grain often get these respiratory symptoms sooner, or at a younger age, than nonsmokers.

- Toxic organic dust syndrome or TODS (also sometimes called “grain fever”) n Symptoms are flu-like, including chills, flushed face, muscle pain, general body discomfort. TODS follows heavy exposure to grain dusts. Symptoms occur for “new workers” four to six hours after exposure. Other people who’ve been around dust before can come down with TODS a day or two later (“such as on a Monday following a weekend at home,” notes Skjolaas). TODS also can occur after exposure to confinement housing dust and moldy hay.

- Farmer’s lung n Symptoms are flu-like including cough, fever and chills, labored breathing, muscle pain and general discomfort. Farmer’s lung is caused by dust from moldy hay, silage and grain. Symptoms start four to eight hours after exposure. Even small amounts of dust can cause illness after a person becomes sensitized, notes Skjolaas. Farmer’s lung can cause permanent lung damage n and death.

Skjolaas reminds producers to wear masks, and provide their employees with them, too. One-strap disposable dust masks aren’t nearly as effective as two-strap models, that fit better and allow less “air leakage,” says reports. She warns that a simple dust mask won’t protect against fumigants or high concentrations of carbon dioxide resulting from deterioration of wet grain. If carbon dioxide is suspected, don’t enter the area. If you can’t adequately ventilate, measure the oxygen concentration before going in. Don’t enter if it’s less than 19.5 percent, according to Skjolaas. Always follow confined space entry procedures before going into a grain bin.

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