Respiratory disorders secondary to work in hog confinement barns
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Respiratory Disorders Secondary to Work in Hog Confinement Barns. Susanna Von Essen M.D., M.P.H. University of Nebraska Medical Center. Hog Confinement Facilities. Worker Health. There is a lot of evidence that workers have a variety of health risks

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Respiratory Disorders Secondary to Work in Hog Confinement Barns

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Respiratory Disorders Secondary to Work in Hog Confinement Barns

Susanna Von Essen M.D., M.P.H.

University of Nebraska Medical Center

Hog Confinement Facilities

Worker Health

  • There is a lot of evidence that workers have a variety of health risks

  • Main problems identified include respiratory disorders, musculoskeletal problems, hearing loss

    • Work-related infectious disease less common

Why Does Worker Health Matter?

  • Impact on people’s lives

  • Impact on productivity of a farming operation

  • Worker’s compensation claims costs

  • Health insurance costs

Features of the Environment that Affect Worker Health

  • Hog dust

    • Feed particles

    • Fecal matter

    • Bacteria, fungi

      • Endotoxin, peptidoglycan (?), mycotoxins (?)

    • Hair, skin particles

    • Insect parts

Features of the Environment that Affect Worker Health

  • Gases

    • 138 have been identified, only a few linked to worker health problems

      • Ammonia

      • Hydrogen sulfide

      • Carbon monoxide

      • Methane

      • Carbon dioxide

Features of the Environment that Affect the Human Airways

  • What correlates with a cross-shift drop in lung function (FEV1):

    • Total dust > 2.5 mg/m3

    • Ammonia > 7.0 ppm

    • Endotoxin > 0.1 mcg/m3 or 100 EU/m3

      • Reynolds et al, Am J Ind Med 29:33, 1996

Kelleys first paper summarized

Get slide

Holness paper summarized

Pulmonary Function in Workers with Airway Disease Symptoms

  • Spirometry often normal despite cough, chest tightness, shortness of breath on exertion

    • Some workers will have mild airway obstruction

  • See a cross-shift decline in FEV1

    • Is associated with elevated dust, ammonia levels

    • This predicts accelerated loss of lung function

    • It is unclear if this can result in severe airway obstruction

Case history: Doug J.

  • 40 yo swine confinement facility manager with 15 years of work experience who complains of cough, chest tightness and shortness of breath with exertion when he is working.

  • Life-long nonsmoker, no history of asthma

Doug J.: Summary

  • This picture is most consistent with the asthma-like syndrome

  • Management of this problem:

    • Wear a respirator

    • Improve air quality in the barns

    • Inhalers

    • Consider changing professions (this man is now a teacher and his symptoms have persisted to some degree)

Asthma-like Syndrome

  • Cough, chest tightness, shortness of breath on exertion, work-related wheezing

  • Symptoms more common if exposed least 2 hours per day for at least 6 years but can be seen within weeks or months of starting work

  • May also have symptoms at night, daytime symptoms when away from work

  • Better after days or weeks away from work

Asthma-like Syndrome

  • Chest X-ray normal

  • Spirometry may show mild (5-18% below normal) airway obstruction but is often within normal limits

    • Will see a >10% cross- shift drop in FEV1

    • This predicts accelerated lung function loss

    • Normal lung diffusion capacity

Asthma-like Syndrome

  • Bronchoalveolar lavage shows an increase in neutrophils, macrophages, lymphocytes but not eosinophils,

  • Therefore, this is not occupational asthma

Unanswered Questions about the Asthma-like Syndrome

  • Does it lead to moderate or severe airway obstruction?

    • Only anecdotal information available

    • Prospective, population-based studies needed

    • In my experience, this outcome is uncommon unless the worker also smokes cigarettes

      • Hog barn, tobacco effects are additive

    • Little is known about the worker exposed 40+ hours per week

Symptoms of asthma present before work in hog confinement

Moderate, reversible airway obstruction on spirometry

Hog Farmer with Asthma

Asthma in Swine Confinement Workers

  • Asthma is an inflammatory disorder with reversible airway obstruction, often with allergy to specific antigens

    • 5-10% of the population is asthmatic

    • Asthma is not more common in farmers

  • Serologic evidence of sensitization to pig proteins is common but does not correlate with respiratory complaints

Asthma in Swine Confinement Workers

  • Persons with pre-existing asthma are likely to have more difficulty with their disease as a result of the exposure to dust and ammonia

  • Work in this environment contributes to exacerbations of asthma

  • Compliance with medication, respiratory protection important

The Venn diagram

Complaints of nasal, eye and throat irritation in hog confinement workers are very common

Mucous Membrane Irritation Syndrome


  • Acute bronchitis: most clinicians describe it as being an acute illness associated with cough productive of sputum.

  • Appears to be work-associated in some swine confinement workers.

  • Unanswered question: do repeated episodes of acute bronchitis cause chronic bronchitis?


  • WHO definition for chronic bronchitis: daily sputum production for at least 3 months of the year for at least 2 years

    • May or may not be associated with airway obstruction measured by spirometry

    • There is no evidence that this progresses to severe disease unless the worker also smokes

Evaluation of a Worker with Respiratory Complaints

  • A detailed work history should be taken

    • Other jobs/exposures including hobbies

    • Factors that exacerbate or improve symptoms

    • Use of respirators

  • Lung disease history

    • Must ask about smoking, pre-existing asthma, COPD, other lung disease

Evaluation of a Worker with Respiratory Complaints

  • Physical examination

    • Usually normal – rarely hear wheezing

  • Spirometry

    • Easily performed using a portable spirometer

    • Also useful as part of pre-placement exam

  • Chest x-ray

    • Should be done if history suggests other diagnoses, such as lung cancer, heart failure

Management of the Asthma-like Syndrome and Other Airway Disorders

  • Improve indoor air quality

    • Choosing a waste management system that minimizes ammonia, dust from manure

    • Frequent pressure washing, flushing or pumping of manure pit contents

    • Adding fat to feed, choosing a feed and delivery system that minimizes dust

    • Monitoring ammonia levels, air flow

    • Consider using an oil mist to control dust

  • Medications

Assessment of Indoor Air Quality

Assessment of Indoor Air Quality

  • Ammonia is simple to measure

  • Measuring total dust and endotoxin requires industrial hygiene expertise

  • CO2 >1500 ppm is a surrogate measure of poor air quality

    • CO2 is easier to quantify

    • It may be difficult to bring CO2 lower than 3000 in cold weather


  • 2-strap disposable respirator

    • Considered most comfortable by workers

    • Removes about 75% of dust

    • Costs about $2

  • Half-face mask respirator with disposable filters for dust, ammonia

    • Costs about $20


  • Rated by worker protection factor (WPF)

  • Many are difficult to wear for persons with severe lung disease because they must breathe against resistance

  • Difficult to wear if worker suffers from claustrophobia

  • ~1/3 of workers wear them in the hog barn

WPF = 16

WPF = 19


Powered-air Purifying Helmet

  • WPF = 30

  • No resistance

  • Cost ~$500

Other Respiratory/Systemic Disorders Associated with Hog Confinement

  • Poisoning by pit gases

  • Influenza

  • Organic dust toxic syndrome

  • Carbon monoxide poisoning

  • Latex Allergy (?)

Death After Poisoning by Pit Gases

  • Often involves multiple fatalities because rescue is attempted without proper procedures or use of appropriate safety equipment

  • The safety program for the farm should include a plan for rescue should a worker be overcome by pit gases

Causes of Death After Poisoning by Pit Gases

  • Toxicity from exposure to hydrogen sulfide

  • Asphyxiation secondary to displacement of oxygen by gases

    • The air normally has 21% oxygen, 19.5% is the minimum level for safe entry

  • Disabling of worker,  drowning or aspiration of manure  pneumonia, acute lung injury

Hydrogen Sulfide Poisoning

  • Hydrogen sulfide is heavier than air

    • Levels highest just above the floor, in gutters, in the air space above the pit contents and in holding tanks

  • High levels most common in hot weather and after pit is agitated

  • OSHA standard for confined space entry should be followed if pit or tank is entered

Hydrogen Sulfide Poisoning

  • Levels greater than 700 ppm are likely to be fatal to humans

    • Binds to cytochrome oxidase system, blocking cell metabolism

    • The human olfactory system is overwhelmed at 50 ppm

      • “rotten egg” smell of hydrogen sulfide will not be detected when levels are high

NIOSH Recommendations for Manure Pit Entry

  • All manure pits should be ventilated with explosion-proof equipment

    • Methane and hydrogen sulfide can be explosive

  • The atmosphere within the pit should be tested before entry

    • A positive-pressure, self-contained breathing apparatus (SCBA) should be used if oxygen levels low or hydrogen sulfide levels high

Swine influenza can infect humans

It is a variant of Influenza A

It is not known how often this occurs


Organic Dust Toxic Syndrome

  • ODTS is a systemic illness experienced after exposure to large quantities of organic dust by inhalation

  • Seen after work in swine confinement barns, after cleaning grain bins, unloading silos

  • Exposure to endotoxin is the cause

Organic Dust Toxic Syndrome

  • Symptoms begin 4-12 hours after heavy organic dust exposure

    • Consist of headache, myalgias, fatigue, fever, occasionally also cough

    • Often confused with influenza

  • Treatment is aspirin or acetaminophen for fever, rest

  • May predispose to cough, bronchitis

Released by power washing equipment or heaters that are improperly vented

Carbon Monoxide Poisoning

Worker Health Program to Prevent Occupational Respiratory Illness

  • Pre-placement assessment

    • Pulmonary disease history and spirometry

  • Monitoring of respiratory symptoms on a yearly basis by questionnaire

    • Spirometry, medical assessment if symptoms develop

  • Monitoring of air quality in the hog barns

    • Ammonia, carbon dioxide

  • Routine use of respirators

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