Indoor allergens in Minnesota schools and child care centers

Elevated concentrations of allergens in the indoor environment may cause allergic sensitization and symptoms. Occupant exposure to indoor allergens in educational facilities should and can be controlled. This study (1) assessed the presence of indoor allergens in Minnesota schools and child care centers, (2) characterized the distribution of allergens in different materials, and (3) evaluated the effect of building and maintenance interventions on allergen concentrations. Settled dust samples were collected from carpet, vinyl tile floors, and upholstered furniture in six schools and seven child care centers before and after interventions. Interventions included changes to cleaning, ventilation, entry mats, furnishings, flooring, and classroom items. The amount of total dust, culturable fungi, and indoor allergens--cockroach, dust mite, cat, and dog--were quantified in the dust samples. Cockroach and dust mite allergens were generally low and below the detection limit, but one dust mite allergen was detected in some areas. Cat and dog allergens were frequently detected at elevated levels, with half the samples above the provisional sensitization risk thresholds and a few samples above the symptom thresholds. Allergen concentrations were highest in upholstered furniture, followed by carpeting and then vinyl floor tile. Cat and dog allergens were lower after the interventions. Cat and dog allergens, but not dust mite and cockroach allergens, seem to be ubiquitous in child care and elementary schools of the U.S. Midwest. These allergens may contribute to sensitization in atopic individuals and occasionally cause symptoms in sensitized allergic individuals. Fleecy materials that are not adequately cleaned, such as upholstered furniture, appear to be the most significant allergen reservoirs. Modest environmental interventions can be implemented by building staff, which should result in lower allergen concentrations.