Reduction of exposure to laboratory animal allergens in the workplace

Evidence is now accumulating that the prevalence of allergy to laboratory animals is related to the intensity of exposure to animal allergens. Whilst airborne animal allergen concentrations may be influenced by the litter type, cage design and stock density, the effectiveness of methods to reduce personal exposure has not been objectively assessed.

Air samples were collected at 2 L/min and 180 L/min onto polytetrafluoroethylene (PTFE) filters and the rat urinary aeroallergen (RUA) and mouse urinary aeroallergen (MUA) concentrations were measured by radioallergosorbent test (RAST) inhibition.

When 545 mice (11.l mice/m3) were housed in ventilated cages (Thoren Maximiser cage system) operated at positive pressure to the environment, the static MUA concentration (n = 24, median = 0.10 microg/m3) was reduced sevenfold when compared with conventional cage systems (n = 12, median =0.67 microg/m3, P< 0.001). MUA could be further reduced if the ventilated cage system was operated at lower pressure; static samples (n = 1) collected at 180 L/min at negative, ambient and positive pressure registered < 0.003, 0.02 and 0.28 microg/m3, respectively. During cleaning out, the intensity of personal exposure to RUA was apparently reduced twofold when soiled litter was removed by vacuum (n = 17, median = 22.87 microg/m3) when compared with tipping (n = 18, median = 38.15 microg/m3), P = 0.002) although the task took twice as long to perform. The RUA exposure associated with handling rats was'reduced 25-fold when performed in a ventilated cabinet (n = 21, median = 2.67 microg/m3) compared with handling of rats on an open bench (n = 17, median = 54.39 microg/m3, P = 0.0001).

Effective reduction of exposure to animal allergens can now be achieved by the use of ventilated systems both for housing and handling rats and mice providing safety equipment is used correctly. The vacuum removal of soiled litter during the task of cleaning out was less efficient and additional respiratory protection is therefore recommended for this procedure.