Asthma is characterized by airflow obstruction, bronchial hyper-responsiveness, and chronic inflammation of the airways. These responses cause wheezing, shortness of breath, coughing, and tightness in the chest.
The two most common types of asthma are allergic and nonallergic. The type of asthma depends on the triggers and environments that cause symptoms.
Allergic or Atopic Asthma
Allergic asthma, also referred to as atopic asthma, is caused by exposure to allergens such as pollen, mold, pet dander, and so on. These allergy triggers—pollen, for example—may not be present at all times, so asthmatic symptoms vary depending on the season and the environment.
Allergic asthma activates the body’s immune system, which protects the body from harmful foreign substances and microbes. When the body comes into contact with a foreign substance, it releases antibodies to react with or destroy the substance. However, sometimes the antibody release involves the overproduction of an antibody called immunoglobulin E, causing a release of chemical mediators such as leukotriene, prostaglandin, and histamine, which can result in the contractions of airway muscles that characterize an asthma attack.
Nonallergic asthma is triggered by nonallergenic substances such as wood smoke, grain dust, tobacco smoke, fresh paint, cleaners, perfumes, and so on. Symptoms are similar to those of allergic asthma. Repeated exposure to these nonallergenic substances causes the release of chemical mediators (described above) that can cause airway constriction.
Occupational asthma, the type of asthma most commonly associated with agriculture, is typically caused by exposure to a substance in the workplace that enters the lungs and activates the immune defense mechanism. The management of occupational asthma symptoms is impacted by exposure to allergens. Agricultural workers on farms and at grain elevators and food processing plants are at an increased risk of occupational asthma.
Examples of Causes or Aggravators of Occupational Asthma
Agricultural producers are exposed to a wide variety of allergens than can cause asthma or aggravate existing asthma. Additional risk factors for the development of asthma include genetics, gender, allergies, and environmental factors (such as tobacco smoke, mold, and so on).
Some of the triggering agents associated with asthma in agriculture include the following:
Grain dust: Grain dust is commonly found in barns, flour mills, and grain-storage facilities. Asthma resulting from grain dust occurs when a person is sensitized to the grain dust or a dust component.
Bacteria and fungi: Airborne bacteria and fungi (mushroom spores, mold, and so on) residing in agricultural structures can get into the lungs of an agricultural producer. Some of the cellular components of these bacterial and fungal microorganisms can cause an immune response that can result in an asthma attack.
Insects: Mites can be found in most homes and agricultural settings. These extremely small insects feed off organic material and may trigger asthma attacks for some people. Storage mites can be found in storage areas of organic products; dust mites are located wherever there is dust; and red spider mites are located in certain greenhouse crops. Cockroaches and their droppings can also trigger asthma attacks in some people, so it is necessary to clean areas attractive to cockroaches at least every two to three days.
Pesticides: Some of the pesticides used to get rid of pests have been associated with agricultural asthma.
Animal products: Potential allergens from animals include substances that contain proteins, such as dander, saliva, urine, and feces. The breakdown of urea and ammonium excretions can cause a release of ammonia in the environment that can be a respiratory irritant. Feathers and wool can also trigger asthmatic reactions.
- Tobacco leaves
Chemicals: Chemical irritants include polyvinyl chloride vapor and amprolium hydrochloride.
Wood smoke: Burning wood releases a mixture of harmful gases that can cause asthma attacks.
Other Types of Asthma
Other types of asthma include the following:
Viral-induced asthma: Viral respiratory infections, such as the common cold, can trigger an asthma attack.
Nocturnal asthma: Nocturnal asthma refers to asthma that worsens during the night—typically between two and four o'clock in the morning—either due to sinus infection or from the presence of an allergen such as dust mites or pet dander. Often gastrointestinal reflux (heartburn) is worse at night and may trigger an attack.
Reactive Airways Dysfunction Syndrome (RADS): RADS occurs after exposure to high concentrations of airborne irritants, such as chlorine. Asthmatic symptoms develop within 24 hours and may continue for several months or longer. Symptoms may recur with further exposure to high concentrations of the irritant.
Exercise and air temperature (especially cold air) can also trigger a person’s allergic or nonallergic asthma.
Reducing Your Risk of an Asthma Attack
Anyone with symptoms of asthma should have a primary medical care provider. Those with persistent symptoms may need to use a daily controller medicine, usually one that is inhaled, to reduce the chance of a flare-up. In addition, people with asthma should also always have a rescue inhaler available for acute symptoms.
The following actions can reduce allergens on your farm or ranch and limit your exposure to allergens:
- Store grain at recommended moisture-content levels to reduce mold growth.
- Properly ventilate animal-housing areas to reduce the accumulation of ammonia and other gases.
- Frequently remove animal waste to reduce the buildup of ammonia and decrease your exposure to urine and fecal allergens.
- Identify dust hazards at your farm or ranch and reduce exposure by cleaning these areas. Limit your time in dusty areas.
- When cleaning a barn or stable, wet down areas to avoid dust from becoming airborne.
- If you are a farm manager, provide appropriate personal protective equipment (PPE) for your employees.
- Wash your work clothes in hot water at least once per week.
- To protect against dust, bacteria, fungi, insects, and animal products when cleaning, spraying, harvesting, handling grain, or working in an animal-confinement building, wear an N-95 or N-100 disposable particulate respirator that is properly fitted and approved by the National Institute of Occupational Safety and Health (NIOSH).
Double Strap Respirator
(Particulate Respirator. Source: Pennsylvania State University. Agricultural Safety and Health)
- For more information about respiratory illnesses associated with agriculture, click here to link to the article "Respiratory Illnesses Associated with Agriculture."
- For more information about the hazards of grain dust, click here to link to the article "Grain Dust Explosions."
- For more information about PPE and respiratory protection, click here to link to the article "Respiratory Protection on the Farm and Ranch."
Linda M. Fetzer, Pennsylvania State University – firstname.lastname@example.org
Asthma. (2005) Candian Centre for Occupational Health and Safety. Retrieved from http://www.ccohs.ca/oshanswers/diseases/asthma.html.
Asthma. (2012). Centers for Disease Control and Prevention. Retrieved from http://www.cdc.gov/asthma/faqs.htm.
Schenker, M.B.(2005) Farming and asthma. Occupational and Environmental Medicine. Retrieved from http://oem.bmj.com/content/62/4/211.1.full.