REDUCTION OF EXPOSURE TO LABORATORY-ANIMAL ALLERGENS IN THE WORKPLACE

Objectives Evidence is now accumulating that the prevalence of allergy to laboratory animals is related to the intensity of exposure to anim al allergens. Whilst airborne animal allergen concentrations may be in fluenced by the litter type, cage design and stock density, the effect iveness of methods to reduce personal exposure has not been objectivel y assessed. Methods Air samples were collected at 2 L/min and 180 L/mi n onto polytetrafluoroethylene (PTFE) filters and the rat urinary aero allergen (RUA) and mouse urinary aeroallergen (MUA) concentrations wer e measured by radioallergosorbent test (RAST) inhibition. Results When 545 mice (11.1 mice/m(3)) were housed in ventilated cages (Thoren Max imiser cage system) operated at positive pressure to the environment, the static MUA concentration (n = 24, median = 0.10 mu g/m(3)) was red uced sevenfold when compared with conventional cage systems (n = 12, m edian = 0.67 mu g/m(3), P < 0.001). MUA could be further reduced if th e ventilated cage system was operated at lower pressure, static sample s (n = 1) collected at 180 L/min at negative, ambient and positive pre ssure registered < 0.003, 0.02 and 0.28 mu g/m(3), respectively. Durin g cleaning out, the intensity of personal exposure to RUA was apparent ly reduced twofold when soiled litter was removed by vacuum (n = 17, m edian = 22.87 mu g/m(3)) when compared with tipping (n = 18, median = 38.15 mu g/m(3), P = 0.002) although the task took twice as long to pe rform. The RUA exposure associated with handling rats was reduced 25-f old when performed in a ventilated cabinet (n = 21, median = 2.67 mu g /m(3)) compared with handling of rats on an open bench (n = 17, median = 54.39 mu g/m(3), P = 0.0001). Conclusions Effective reduction of ex posure to animal allergens can now be achieved by the use of ventilate d systems both for housing and handling rats and mice providing safety equipment is used correctly, The vacuum removal of soiled litter duri ng the task of cleaning out was less efficient and additional respirat ory protection is therefore recommended for this procedure.