Rapporteur: Peter S. Thorne, Ph.D.
Participants: Kelley J. Donham, D.V.M., The University of Iowa
James Dosman, M.D., University of Saskatchewan
Paul Jagielo, M.D., The University of Iowa
James A. Merchant, M.D., Dr.P.H., The University of Iowa
Peter S. Thorne, Ph.D., The University of Iowa
Susanna von Essen, M.D., University of Nebraska
Agriculture has historically been an occupation with notable health and safety hazards. In the late 1960s and early 1970s, swine production came "indoors" in the United States. This led to the first description of health hazards to people working in these facilities in 1977. Since then, more than 25 studies have been conducted on swine worker health in the United States and Europe. It appears that more workers are going to spend longer hours in animal confinement buildings. This will likely lead to increased exposure and greater risk of adverse health effects.
1. Health risks for persons working inside swine confinement production facilities.
A. Types of problems and symptoms.
The principal health risks for swine workers result from a wide range of hazards. Chemical, biological (non-infectious), and infectious hazards have received considerable attention. In addition, noise, trauma, fires, explosions, electrocutions, thermal stress, poisonings, and drownings are important causes of morbidity and mortality. Often overlooked are emotional stress, chronic pain, and fatigue, which can lead to significant impairment and put the worker at additional risk. Most of these are readily understood and preventive measures are established and available, but often not implemented. Respiratory disease in swine confinement workers receives even less preventive attention.
Inhalation exposures are common and lead to significant morbidity among swine farmers. There are confined space entry hazards in swine farming and related deaths from hydrogen sulfide are not uncommon. Respiratory problems associated with this environment include upper respiratory tract, airways disease, interstitial, and mixed airways and interstitial lung diseases. Lung disease in swine confinement consists of acute and long-term lung insults that may lead to chronic declines in lung function.
Frequent upper respiratory tract problems include sinusitis and rhinitis. Sinusitis is often chronic in confinement workers. They complain of a stuffy head, difficulty in breathing through the nose, headache, and "popping ears."
Bronchitis is the most common complaint of workers, effecting as many as 70 percent of exposed persons. This is an inflammatory-induced irritation of the airways. It may lead to chronic bronchitis, a condition with chronic cough and phlegm production. This condition effects about 25 percent of swine producers in confinement.
Occupational asthma includes periodic airways obstruction, chest tightness, wheezing, and dyspnea, but does not occur on first exposure. Occupational asthma is associated with repeated exposure to the work environment. Nonallergic occupational asthma, or reactive airways disease, is common (20 percent) of current swine workers. This condition may lead to chronic obstructive pulmonary disease, which is a permanent, possibly disabling condition.
Organic dust toxic syndrome (ODTS) results in a flu-like spectrum of symptoms with headache, joint and muscle pain, arthralgia and myalgia, fever, fatigue and weakness, and irritation of the airways and the cells lining the small sacs of the lung. Thirty-three percent of swine producers have reported episodes of ODTS.
A chronic or subacute condition (a variant of ODTS) more frequently seen in swine workers is marked by chronic fatigue and possibly persistent mild pulmonary infiltrates. This may represent a similar syndrome caused by simultaneous exposures to bioaerosols and irritant gases.
Acute respiratory distress syndrome (ARDS) or pulmonary edema can result in swine workers from acute or chronic exposure to hydrogen sulfide. There have been at least 19 acute deaths in workers resulting from sudden exposure.
It is recognized that several of these conditions may occur in an individual swine worker and they may occur at the same time. It is likely that an individual worker may have signs and symptoms of an asthma-like condition, bronchitis, and episodes of ODTS.
B. Time for symptom development.
As little as a two-hour daily exposure may initiate acute symptoms, and six or more years of exposure increases the risk for chronic symptoms. For individuals with underlying pulmonary disease, e.g., asthma, only a few minutes may be sufficient exposure time for symptoms to develop. It is believed that if these individuals elect to work in swine production at all, they will leave this occupation in the first three months of employment.
C. People at higher risk.
There is evidence to suggest that individuals with symptoms or a history of respiratory, heart, allergic disease, or smoking are at greater risk. Exposures to irritant particles and gases in swine farming may encourage early selection out of the occupation when compared to grain farming or cotton dust exposure environments.
D. Early signs of impending health problems.
There is sufficient evidence that acute cross-shift change in lung function is predictive of longitudinal lung function decrements. Additionally, at least two studies have shown that lowered baseline pulmonary function is associated with declines in pulmonary function over a work period.
The following are warning signs of impending health problems:
E. Reversibility of damages or health problems.
It is likely that some of the lung problems experienced by swine workers do cause irreversible damage. However, there are unpublished anecdotal cases observed that some acute lung illnesses are probably reversible. It should be realized that reversible health problems should still be prevented.
F. When to quit.
The major concern for work restriction in swine confinement workers are, periodic acute airways obstruction, progressive decline in lung function, and episodes of reactive airway disease. Some respiratory conditions have a significant risk for disability or may be life threatening. Conditions for advising restriction from working in swine confinement facilities follow.
Asthma: Asthma marked by severe airways obstruction, chest tightness, wheeze, or dyspnea is grounds for restriction from exposure and work in swine confinement buildings.
Asthma-like Syndrome: It is likely that use of respiratory protection for those activities that are most hazardous and general operational improvements to reduce exposures to bioaerosols and irritant vapors will allow continued work in swine production.
Chronic Bronchitis: It may be acceptable for the farmer to continue work in swine confinement with chronic bronchitis.
2. Containing worker health risks.
Worker health risks can be significantly reduced through a comprehensive program of environmental monitoring and control by use of management practices, engineering controls, judicial use of personal protective equipment, and health surveillance. However, such programs are exceedingly rare in today's swine industry.
Special attention should be given to pregnant women who work in swine confinement facilities. Aside from increased susceptibility to carbon monoxide and potentially other gas and vapor exposures, pregnant women may be at increased risk for spontaneous abortion if they work in swine barns. More exposure control and surveillance is appropriate for this group of workers.
Noise induced hearing loss is a problem in this occupation since the sound pressure levels of squealing sows in swine barns routinely exceeds 100 dBA. The simplest approach to prevention of noise induced hearing loss in this environment is through the proper use of protective devices such as ear plugs or semi-aural caps.
3. Extrapolating risks associated with working inside swine confinement facilities to exterior environments.
There is limited utility in attempting to extrapolate occupational health risks from inside swine facilities to community health risks outside swine production. Although there is discharge of airborne particulates and vapors from the swine barns to the outside environment, the aerosols differ considerably in composition and concentration of specific agents.
4. Evidence to indicate changes in the intensity and duration of worker exposures affects the health of swine confinement workers.
The intensity and duration of exposure is expected to differ between large-scale swine production facilities, contract grower operations, and owner-operator facilities. The duration of exposure is variable. Automation tends to decrease exposure time while work at large facilities and operations with farrowing and nursery grower units tends to increase exposure duration. Across the industry, time spent inside swine barns is likely to increase with the movement toward large-scale swine production. The benefits of lower exposure concentrations may be entirely offset by the longer exposure times.
5. What is the impact of the proliferation of large-scale confinement production facilities on the above issues?
Exposures and related occupational risks will increase with proliferating large facilities. This is mainly due to longer exposure periods. Increased risk does not have to happen if proper controls are implemented. Health and environmental surveillance by the Occupational Safety and Health Administration (OSHA) will increase as large-scale swine production expands. A shift toward large-scale swine production has the potential to greatly improve health and safety and with it come some significant cost benefits. There is a need for large-scale swine producers to have model surveillance programs they can implement.
A second important potential impact of the proliferation of large-scale swine production facilities is the impact on public health. It is believed that these facilities will draw laborers from outside the surrounding communities, including immigrant or migrant laborers, and this will have an important impact on social services and health services in these communities.
6. Elements of a complete occupational health program.
Elements include an education and training component; an agricultural hygiene program geared toward recognition, evaluation and control; a health surveillance program; an emergency preparedness program; and an employee assistance program, and the staff to oversee such a program.
7. Insurance reductions for compliance with an occupational health program.
Insurance reductions for providing a safer work environment can result in a significant cost savings. When combined with health care cost savings, reduced worker compensation costs, lower worker compensation coverage rates, lower absenteeism, and lower worker turnover, these can result in a net savings for the producer. State and National Pork Producers Council organizations could promote a "good standards occupational health and safety program" that insurance companies would support and provide strong incentives for.
8. Safe and economically achievable limit values for dusts and gases.
There are no U.S. federally mandated permissible exposure levels for dusts or gases specifically for swine confinement facilities. It is widely held that general industry standards for many individual toxicants are not protective for the complex mixture of inhalation exposures in the swine environment.
9. Effective and economically achievable methods of environmental assessment for dusts and gases.
Effective and economically achievable methods of environmental assessment for dusts and gases have been developed by the National Institute for Occupational Safety and Health (NIOSH). Personal noise dosimeters are commercially available for determination of noise exposure.
10. Effective protocol and delivery system for assessment.
There currently is a paucity of agricultural hygiene and laboratory services available to aid swine production facilities in exposure assessment and few producers have the capability to perform these functions in-house. A network of regional hospitals and clinics has been organized in Iowa to provide occupational services to farmers and such networks could disseminate information concerning environmental assessments. There is a need for NIOSH or perhaps a university-based agricultural research center to issue current intelligence bulletins addressing medical management, environmental measurement options, and environmental and administrative controls.
11. Requirements of OSHA or other regulations and liabilities to employers for worker health in livestock production.
This issue should be referred to legal experts who are aware of federal and state laws pertaining to the strict legal definition of agriculture; Department of Labor and OSHA jurisdiction in agriculture; the workers compensation responsibilities of agricultural employers; protection of workers that are employed less than 100 days, providing bartered labor, or are extended family members; and personal injury law in agriculture. In addition, contract law is an important element because many smaller producers function as independent contractors who own the swine facilities on their property but do not own the hogs. Liability and responsibility under these circumstances may differ from one contract to the next.
12. Additional issues.
There is a need for increased education of primary health care providers in identification, treatment and prevention of lung disease and other injuries in swine production workers. There are many important research questions that need to be addressed in order to improve worker health and the environmental impact of swine production. Occupational health research in agriculture has traditionally been underfunded compared to other industrial sectors.
A long-term prospective study is the highest research need. Although these are expensive and time consuming studies, they are the best way to confirm answers to many of the questions that presently need confirmation or more complete answers. Questions of particular concern are the long-term health outcomes of workers, economic impact, and insurance incentives for effective health programs. A follow-up study of previously studied worker cohorts also has a high priority to help answer some of the most important questions listed above.
Treatment regimes including environmental exposure controls, personal protection, and the effectiveness of medical management plans are critically needed. We must be able to appropriately and ethically manage affected individuals in the work force for their own benefit and that of the livestock industry.