Closed for Recruitment
Study / Trial Background
Exposure to indoor allergens has been associated with an increased risk of development of allergic sensitization and asthma symptoms among susceptible children. Most studies that have examined these relationships have used allergen levels in the child's home as the relevant measure of exposure because young children typically spend most of their time at home. However, many children in the United States spend significant proportions of their time in day care. In 1997, 63% of the country's 19.6 million children under 5 years of age were in some form of regular child care during a typical week. These children were cared for in organized child-care centers and in residences. On average, they spent 37 hours per week in child care.
Although there have been reports on allergen levels in day-care facilities in other countries, such as Brazil, France, Germany, Singapore, and Sweden, little information has been reported from the United States. The only published study we are aware of examined dust mite, cat, and cockroach allergen in 20 day-care centers in Tampa, Florida. That study found dust mite allergen (Der f 1 or Der p 1) in floor dust samples from 10 centers and in air samples from 18 centers. Eight of the floor dust samples had dust mite allergen levels high enough to cause allergic sensitization. Cockroach allergen (Per a 1) and cat allergen (Fel d 1) were detected in all 20 centers.
This study evaluated allergen levels and their predictors in day-care facilities in 2 North Carolina counties. The purpose was to determine whether further study of day-care facilities on a regional or national basis is warranted and to identify associations that might be important to evaluate in larger studies.
In 2002, NIEHS investigators conducted a survey of 89 day care facilities in two North Carolina counties. That survey measured levels of seven allergens and investigated the relationships between those allergens and characteristics of the day care facilities. Both child care centers and child care homes were included in the survey.
The purpose of the study was to:
- estimate the prevalence of allergen exposures in day care facilities
- identify modifiable predictors of allergen levels in the facilities
- determine whether further study of day care facilities on a regional or national basis is warranted
In this survey of day care facilities, detectable levels of Alternaria, cockroach, dog, dust mite, cat, and mouse allergens were commonly found. For many young children and day care staff, day cares may be a source of clinically relevant exposures to several indoor allergens. Further studies of day care facilities need to be conducted in order to characterize allergen exposures in other regions of the country, to identify modifiable predictors of allergen levels, and to examine relationships between allergen exposures in day care facilities and health outcomes in children and day care workers.
See Related Publications for further information about this study.
What will you do?At each facility, a questionnaire was administered to the manager or administrator, observations were made of the sampled room (the room where most of the children spend most of their time), and vacuumed dust samples were collected. A technician recorded observations of the sampled room and collected either a carpet sample, a hard-surface sample, or one of each if both surfaces were present. For a given sample, the technician marked off as many as four 1 m2areas and vacuumed these areas at a rate of 1 m2 per 2.5 minutes. Vacuuming was performed with a Eureka Mighty-Mite 10-ampere vacuum cleaner (Eureka Co, Bloomington, Ill). The dust-collection device, which was also used in the National Survey of Lead and Allergens in Housing, was a 19 mm × 90 mm cellulose extraction thimble (Whatman International, Ltd, Middlesex, England) fitted into the distal end of the vacuum's extension tube, sealed with a rubber O-ring placed around the circumference of the thimble, and covered with a crevice tool.
What will NIEHS do?At the laboratory, dust samples were sieved through 425-μm pore grating and weighed. Sieved dust was extracted in PBS and clarified by means of centrifugation. Supernatants were decanted and stored at −20°C. Allergen concentrations were measured with ELISAs. Bla g 1, Can f 1, Der f 1, Der p 1, and Fel d 1 were measured with mAb-based ELISAs from Indoor Biotechnologies, Inc (Charlottesville, Va); Mus m 1 was measured with a polyclonal antibody–based ELISA from Indoor Biotechnologies, Inc; and Alternaria alternata was measured with a polyclonal antibody–based ELISA from Greer Laboratories, Inc (Lenoir, NC). Because the A alternata assay is based on a polyclonal antibody raised to an A alternata extract, it reacts to a variety of A alternata proteins, which could result in a higher concentration than if the assay had been to a specific protein, such as Alt a 1. The other assays were based on antibodies raised to a specific protein. These differences should be considered when the allergen concentrations are compared with one another.