About eight percent (24 million) of Americans suffer from asthma.1 Asthma symptoms include shortness of breath, chest tightness, and coughing. The majority of asthma cases are caused by allergies to plant pollens and environmental dusts; somewhat less common are those produced by dust mites, insect parts, and animal dander.
Much research today involves the use of animals and work with laboratory research animals resulting in allergies is one of the most common health hazards faced each day. Allergic reactions, which are a result of immunological and biochemical mechanisms, are not perfectly understood. Therefore, laboratory animal allergy (LAA) remains a serious occupational hazard.
LAA begins with exposure to the allergens that are usually enzymes, proteins, or glycoproteins. Animal allergens are found in urine, saliva, dander, and fur of research species including rats, mice, cats, dogs, horses, and birds, among others. The exposure route is most often airborne allergens, but skin contact can also produce reactions referred to as contact dermatitis.
Rats are perhaps the most common research animal species. The major sources of rat allergen appear to be urine and saliva. Research has shown that handling rat litter can introduce a large amount of allergen, particularly smaller particles that can remain airborne for 15 to 35 minutes.2 Mice, which also produce a urinary protein, are another major source of allergen for animal lab workers.
Dogs and cats pose a significant risk of sensitization both in the laboratory and outside the work environment (because they are also kept as domestic pets). Cat allergens, produced in saliva and sebaceous glands of the skin, are unique in that they appear to be highly electrostatically charged and therefore tend to stick to surfaces, which then act as reservoirs holding and transferring allergens even in the absence of cats. One other major species worth mentioning is birds; exposure to which can cause rhinitis and hypersensitivity pneumonitis, a potentially serious pneumonia-like lung condition.
Most workers that develop allergies to lab animals do so within one to three years of first exposure.2 Persons with pre-existing allergic conditions such as hay fever are at greater risk of developing LAA.
Duration of exposure and allergen concentration are also important risk factors. Airborne allergen concentrations are directly proportional to the number of animals in the area and depend on the rate of production minus the rate of removal. This suggests that ventilation is central in limiting exposures. However, at least one study has shown that although ventilation is effective for lowering concentrations when allergen production is low (e.g. small numbers of animals), it might take up to 127 air changes per hour (ACH) to significantly reduce exposures when allergen production is very high, such as during cage cleaning or in densely populated areas.2
Experience shows that exposure concentrations are also definitely related to specific tasks. Cage-cleaning ranked at the top, followed by handling, and then surgery/euthanasia. Research has shown that airborne allergen concentration increased up to five times and small particles (less than 1 micron average diameter) increased three times in areas where cage cleaning was conducted. Sampling methods are available to measure airborne allergen concentrations as well as particle size. It is important to keep these facts in mind when developing your prevention program.
LAA usually begins with nasal symptoms like sneezing and a runny nose, itchy, watery eyes, and/or rashes. Skin conditions such as hives or rashes can develop with simple contact. Medically, these are referred to as contact dermatitis.
A more serious condition that might affect about 10 percent of workers is occupational asthma that can cause coughing, wheezing, and shortness of breath and lead to chronic symptoms that continue even after exposure is removed.
Preventive measures and allergen control
LAA is an important occupational health hazard and a difficult problem to solve. The first step is to develop a comprehensive prevention control plan for your facility. The National Institute of Occupational Safety and Health publication, Preventing Asthma in Animal Handlers, provides solid recommendations for your control program.3 Another excellent guidance document is the National Institute of Health’s Laboratory Animal Allergy Prevention Program.4
The recommendations in these publications can be grouped into two main categories: engineering controls that involve facility design and specialized equipment; and administrative controls that include employee screening, work protocols, and personal control measures.
Engineering controls are the most important and definitely the most expensive part of a good prevention control program. Facility design and ventilation are two major components. Since we know that aeroallergen loading is equal to allergen production (a function of the number of animals and, to a lesser degree, the species) minus the removal (a function of the ventilation controls) we should strive for the best ventilation systems we can. The ideal is likely a single-pass ventilation system where 100 percent of supply is exhausted, but this is very expensive.
If recirculation is necessary, use of high efficiency particulate air (HEPA) filtration is strongly recommended, which is also expensive both to install and maintain. The next best solution is the use of local exhaust ventilation, biological safety cabinets, specialty hoods, back-draft and down-draft workstations. These are designed and set up for specific tasks and are effective controls.
No matter what type or combination of ventilation you use, a final (as well as routine) test and balance of the system is needed to ensure optimum performance and that appropriate pressure gradients exist for maintaining air flow and isolating the controlled areas.
Following ventilation, state-of-the-art equipment for animal research facilities is paramount. Included here are filter-top cages, ventilated cage and rack systems, or individual ventilated cages, all with or without HEPA filtration. In addition, there are now automated systems for cage-emptying/changing, cage washing, and waste handling. As with ventilation, a major downside is the cost.
The things we can do administratively and procedurally include implementation of policies, and are referred to as administrative controls. One of the most important is a pre-placement screening evaluation of employees for risk factors such as symptoms or history of allergy or asthma, or specific allergy to animals (pets or laboratory). Pulmonary function measurement (e.g. spirometry) is also encouraged. Finally, regular health surveillance is recommended by both NIOSH and NIH.
Additional administrative controls to consider when developing your LAA prevention program are controlling access and isolating the animal handling areas. Only a minimum number of workers should be authorized entrance. Transport of animals should be well planned. Segregate the “clean” tasks from the “dirty” ones.
Choice of bedding material is also critical. For example, the NIH recommends using hypoallergenic corncob or recycled wood product and wetting the bedding prior to changing or dumping to minimize allergen concentrations.4
Education and training of employees is a large part of preventing LAA. Every worker must clearly understand the risks and possess awareness of allergy symptoms. Knowledge of prescribed work practices and proper use of equipment and personal protective gear such as gowns, gloves, head and foot coverings, and respirators are essential. The importance of good personal hygiene (e.g. hand washing) and prompt reporting of any development of symptoms cannot be stressed enough.
- Occupational Asthma. Dr. David Weissman. Centers for Disease Control and Prevention. December 2017. https:// tools.cdc.gov/medialibrary/index.aspx#/media/id/353830
- Occupational Health and Safety in the Care and Use of Research Animals. National Research Council. National Academy Press. Washington, D.C. 1997
- Preventing Asthma in Animal Handlers, National Institute of Occupational Safety and Health. Publication 97-116. January 1998. http://www.cdc.gov/niosh/docs/97-116/
- Laboratory Animal Allergy Prevention Program, National Institute of Health, Division of Safety. January 2003. http://www.ors.od.nih. gov/sr/dohs/Documents/LAAPP.pdf