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Farmer's Lung: The Risks and How to Reduce Them

Farmer's Lung: The Risks and How to Reduce Them

Farmers Lung is an allergic disease caused by inhaling allergy-causing dust found in some agricultural operations. A few real-life examples of its impact:

A 38 year-old man was feeding out wrapped bales of hay in the winter. The man stuffed the waste plastic wrap behind the seat in the cab of the tractor as he fed the bales. The wrapper had not properly sealed the plastic resulting in mould under the plastic. As a result, he now has weakness and shortness of breath and 50% lung capacity.

A 66 year-old dairy farmer experienced shortness of breath starting in his 40s. He has fibroses in the lungs, is on oxygen full time, and has been recommended to undergo a lung transplant.

A 22 year-old male with pre-existing asthma was harvesting corn. He was overcome with sudden respiratory failure and died due to exposure to mouldy corn.

All of these farmers inhaled dust containing mould spores that caused permanent, irreversible lung damage.

Watch for These Symptoms

Symptoms of Farmer's Lung can occur as soon as four to eight hours after exposure to dusts and mould spores. They may include headache, irritating cough, and shortness of breath upon physical exertion as well as *:

Symptoms can persist for up to two weeks without further exposure. Depending on the degree and frequency of exposure, symptoms may increase in severity and can become debilitating and long-term. After multiple exposures, it takes less of the dusts and mould spores to set off the reaction in the lung. Smoking can make the condition worse.

The presence of Farmer's Lung is mostly observed after the harvest season when symptoms have set in. It peaks during late winter and early spring.

Treatment includes steroids and oxygen therapy. However, these do not heal damaged lungs although they help sufferers cope with the condition. Farmers with severe damage to their lungs from Farmer's Lung are put on a waiting list for a lung transplant. 

The Risks and How to Reduce Them

Moulds tend to grow in stored hay, grain, or silage when moisture content is high (30 percent) and storage areas are poorly ventilated. People can be exposed to harmful dusts and moulds if they are:

  • feeding or working with hay, grain or silage
  • working in dusty fields or buildings
  • working in silos or grain bins
  • working around animal feathers, hair, fur or droppings

Here are some recommendations for eliminating or reducing exposure to dusts and mould spores:

  • Maximize ventilation in dusty areas
  • Ensure adequate ventilation in barns, grain bins and silos by using fans or roof vents
  • Maintain ventilation systems for optimum performance
  • Avoid dusty work in enclosed spaces
  • Dry wet materials before processing
  • Wet dried or dusty material before cleaning
  • Replace dirty air filters in the tractor
  • Consider respiratory protections if the above measures are not feasible or effective in reducing exposure to dusts and mould spores

Take every precaution possible to prevent yourself and others on your farm from breathing in dusts and mould spores. Enjoy healthy lungs for the rest of your days!

For more information on respirators, consult our Agricultural Topic Fact Sheets:

Respirator Fit

Properly Cleaning and Storing Respirators


Canadian Centre for Occupational Health and Safety (2016, November 2). OSH Answers Fact Sheet: Farmer's Lung

Dales, R. E., & Munt, P. W. (1982). Farmer's Lung Disease. Canadian family physician Medecin de famille canadien, 28, 1817-1820

Farm Safety Association. (1990, March). Farmer's Lung: It takes your breath away!. Fact Sheet No. F-014.