Purpose of the Study
To investigate the levels of major indoor allergens in the settled dust and air in hospitals and determine the effects of regular vacuuming on allergen levels in hospital chairs.
House dust mite (Der p 1), cat (Fel d 1), dog (Can f 1), and cockroach (Bla g 2) allergen levels were measured in dust collected from 83 carpeted floors, 69 mattresses, and 42 upholstered chairs in 14 British hospitals. The hospitals included six private and eight public hospitals that provided both adult and pediatric care. Airborne samples were also collected from the outpatient department of one of the participating hospitals. Samples were collected using standard techniques and allergen levels were measured by enzyme-linked immunosorbent assays (ELISA). To compare the effects of vacuuming on dog and cat allergen levels, dust samples were collected from 36 upholstered chairs on four separate occasions at 4 weekly intervals from a busy outpatient chest clinic. During the 12 intervening weeks, 18 of the chairs (active group) were cleaned by vacuuming for 1 minute using a vacuum cleaner with a high efficiency particulate air (HEPA) filter. The remaining 18 chairs served as controls. There was no significant difference in baseline levels of cat or dog antigen in the controls versus the active chairs.
Dust mite, cat, and dog allergen levels were significantly higher in upholstered chairs than in carpets or mattresses. There was no correlation between the age of the carpet, mattresses, or chairs and the levels of antigen detected. Cockroach allergen was below the detection limit of the assay in all the dust samples from the hospitals. No differences were found among the sampling sites from the different hospitals. Dog antigen was found in the air using high-volume samplers on 10 separate days in the outpatient department of one of the hospitals. Detectable cat antigen was found on 7 out of 10 days, but no measurable airborne dust mite or cockroach antigen was found. Repeated vacuuming of upholstered chairs in the outpatient clinic significantly reduced the settled dust levels of both cat and dog antigen in the active group versus the control group. For example, dog allergen levels decreased from a mean of 8.4 μg/chair at baseline to 0.5, 0.2, and 0.15 μg/chair at weeks 4, 8, and 12, respectively. Cat allergen levels decreased from a baseline mean of 6.9 μg/chair to 0.4, 0.3, and 0.3 μg/chair, respectively, with regular vacuuming.
The low levels of dust mite in the hospitals was thought to be related to the typically low humidity in the UK hospitals, found in one hospital studied to be consistently <45%. Hospital ward carpets were also vacuumed daily and hospital mattresses are encased in vinyl covers that are impermeable to dust mites. High levels of cat and dog allergen measured in upholstered hospital chairs were probably brought in on the clothing of cat and dog owners. The cost effectiveness of additional cleaning techniques required to reduce allergen levels would have to be weighed against the cost of more suitable furnishings and flooring.
Upholstered chairs in hospitals may constitute a significant reservoir for cat and dog allergen. Thorough vacuuming of chairs could reduce the levels of cat and dog antigen.
This study supports findings from other studies that cat and dog allergens are ubiquitous, having been found in various public buildings, schools, day care centers, homes, and now hospitals. The fact that levels of antigen in vinyl encased hospital mattresses were relatively low is encouraging, although the high levels of antigen in upholstered chairs should discourage their use, particularly in clinical areas where potentially sensitive asthmatic patients are cared for. Regular vacuuming of upholstered chairs seems a reasonable alternative although no mention was made of the effects of vacuuming on airborne allergen levels, which are most important in causing symptoms.