Number of rats

Figure 7.4. Effect of reducing stock density. Rat urinary aeroallergen concentrations measured when the stock density was reduced from 3 (1 to no rats m3 (60 to no rats). The measurements made on cleaning-out days are shown as open circles. The geometric mean (GM) is indicated. (Gordon, S. et al., Br. J. Ind. Med., 49:416-422, 1992. Reproduced with permission.)17

brushing and the use of portable vacuum cleaners, should be avoided, as they can create high amounts of airborne particles contaminated with allergen. The use of power-washing systems, using high-pressure water, can generate contaminated aerosols and should be avoided where possible. Where power washing is used, appropriate personal protective equipment should be worn.

The contaminated outputs from animal work must be controlled. There should be procedures to control exposure to allergen in the handling of contaminated documents and in the disposal and handling of animal carcasses and tissues, animal waste and bedding, and contaminated personal protective equipment. Measures should be implemented to minimize the need for documents in animal holding and handling areas, such as using computers with washable-plastic-covered keyboards for documentation, connected to printers outside of the animal department. Clean documents can be created in a scanning (but not photocopying) process. If documents need to be retained (and archived), then measures should be taken to minimize spread of allergen from the facility. Contaminated records and archives are an important potential source of allergen exposure because they provide a mechanism by which workers with serious LAA can be inadvertently exposed

Procedures should be implemented to reduce exposure to allergen during the laundry of reusable protective clothing. The risk to laundry workers, who may not be aware of animal allergen risks, should be considered. Soluble laundry bags that can be sealed in the animal facility and dissolve during the laundering process are available.

Cage cleaning has the potential to expose workers to high aeroallergen levels.15 Care must be taken to reduce allergen spread from this source at all points of handling. Dedicated equipment that minimizes contact with soiled bedding should be provided in the cage-washing area. Several commercially available systems have been described. Common to all of these is that cages are emptied into closed transport systems that deliver bedding to different types of sealed containers. Vacuum cleaning systems that are designed not to generate local contaminated exhaust have been used, and result in low levels of allergen during floor cleaning.56 However, these measures will not necessarily contribute to reductions in personal exposure if they do not enable efficient completion of the task.69

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