Many people associate farming with fresh air and a healthy, robust environment in which to work and live. However, much of the air that farmers breathe is dirty and sometimes lethal. Farmer’s Lung and Organic Dust Toxicity Syndrome (ODTS) are names given to two farm occupational diseases caused by inhaling airborne mold spores. Mold spores are produced by microorganisms which grow in baled hay, stored grain or silage with a high moisture content (30 percent). They become active when temperatures reach 70°F in poorly ventilated areas. Farmers most often suffer from these diseases in winter and early spring because the molds have had time to develop in closed storage areas.

Heavy concentrations of mold spores appear as a dry, white or grey powder in grain or forage. When the feed is moved, billions of these microscopic-sized particles become airborne and attach themselves to dust. These particles pass through the body’s natural filtering mechanisms (nose, hair, and throat mucous) and accumulate in the lungs where they can cause an allergic type of pneumonia. Repeated attacks can lead to scarring of lung tissue, which impairs its function. Such tissue damage is permanent.

Exposure to mold spores may produce the following symptoms: First, there is a delayed reaction of three to eight hours during which the patient may develop shortness of breath; tightness in the chest; fatigue; a dry, unproductive cough; muscle ache, headache, chills and fever. The most serious stage of the reaction may last approximately 12 to 48 hours, but some effects are likely to linger for up to two weeks.

Acute exposure symptoms eventually disappear with no apparent lasting effect, particularly with first- time or mild exposures. Occasional mild symptoms are most often dismissed as bouts of flu or other illness. The result is that the diseases are often not properly diagnosed until the symptoms have become severe and constant.

There are several management practices that can either help prevent the growth of mold spores or limit the damage they can cause. Using mold inhibitors, baling hay, ensiling crops, and harvesting and storing grains at the recommended moisture content limits mold spore growth. It also maximizes the quality of your feedstuffs.


Converting to mechanical or automated feeding or feed-handling systems can reduce the amount of airborne mold spores or can reduce human exposure. Wetting down materials before use may help keep spore distribution to a minimum.

Respiratory protection is the last line of defense against Farmer’s Lung and ODTS. The proper type respirator can protect those who have not contracted the diseases or help prevent the diseases from getting worse. Particulate respirators are available at your local pharmacy or from your agricultural chemical supplier. These are approved for protection against dust, such as asbestos, and they provide inexpensive protection against mold spores. More expensive and sophisticated respiratory devices may be required occasionally.

Commonly available disposable respirators for nuisance dusts are not effective against the tiny mold spores. Farmer’s Lung and ODTS are two of the most serious health hazards found on most farms. Yet, through good management practices and respiratory protection, you can completely avoid these diseases. Don’t wait until you are permanently impaired before you take action. PD

Excerpts from Penn State University Extension website

Dennis Murphy