Bedroom allergen exposures in US households

Abstract

Background: Bedroom allergen exposures contribute to allergic disease morbidity because people spend considerable time in bedrooms, where they come into close contact with allergen reservoirs.

Objective: We investigated participant and housing characteristics, including sociodemographic, regional, and climatic factors, associated with bedroom allergen exposures in a nationally representative sample of the US population.

Methods: Data were obtained from National Health and Nutrition Examination Survey 2005-2006. Information on participant and housing characteristics was collected by using questionnaires and environmental assessments. Concentrations of 8 indoor allergens (Alt a 1, Bla g 1, Can f 1, Fel d 1, Der f 1, Der p 1, Mus m 1, and Rat n 1) in dust vacuumed from nearly 7000 bedrooms were measured by using immunoassays. Exposure levels were classified as increased based on percentile (75th/90th) cutoffs. We estimated the burden of exposure to multiple allergens and used multivariable logistic regression to identify independent predictors for each allergen and household allergen burden.

Results: Almost all participants (>99%) had at least 1 and 74.2% had 3 to 6 allergens detected. More than two thirds of participants (72.9%) had at least 1 allergen and 18.2% had 3 or more allergens exceeding increased levels. Although exposure variability showed significant racial/ethnic and regional differences, high exposure burden to multiple allergens was most consistently associated with the presence of pets and pests, living in mobile homes/trailers and older and rental homes, and living in nonmetropolitan areas.

Conclusions: Exposure to multiple allergens is common. Despite highly variable exposures, bedroom allergen burden is strongly associated with the presence of pets and pests.

Keywords: Allergen; allergy; exposure; home; indoor.

Figure 1

Prevalence (±SE) of exposure to detectable bedroom allergen levels in the US population.

Figure 2

Exposure to multiple allergens in bedrooms. Percentages (±SE) of NHANES 2005–2006 participants with detectable (A) and elevated (B) levels of allergens by numbers of allergens exceeding allergen-specific thresholds (LOD, 75^th/90^th percentile). Can f 1, Fel d 1, Der f 1, and Der p 1 levels were elevated if allergen concentration >75^th percentile; Alt a 1, Bla g 1, Mus m 1 and Rat n 1 levels were elevated if allergen concentration > 90^th percentile.

Figure 3

Prevalence of elevated allergen levels by census region. Can f 1, Fel d 1, Der f 1, and Der p 1 levels were elevated if allergen concentration >75^th percentile; Alt a 1, Bla g 1, Mus m 1 and Rat n 1 levels were elevated if allergen concentration > 90^th percentile. The dark background color in the map indicates statistically significant differences (P < 0.05) across US census regions (Northeast, Midwest, South, West).

Figure 3

Prevalence of elevated allergen levels by census region. Can f 1, Fel d 1, Der f 1, and Der p 1 levels were elevated if allergen concentration >75^th percentile; Alt a 1, Bla g 1, Mus m 1 and Rat n 1 levels were elevated if allergen concentration > 90^th percentile. The dark background color in the map indicates statistically significant differences (P < 0.05) across US census regions (Northeast, Midwest, South, West).

Figure 4

Independent predictors of elevated allergen levels. The odds ratios from multivariable regression models are presented in the online repository (Table E4). For the independent predictors, the solid red/blue color indicates the direction of the associations (red increasing; blue decreasing) when each of the participant/housing characteristic categories were compared to the reference category adjusting for the other independent predictor variables in the model. The dashed areas indicate participant/housing characteristics included in initial prediction models based on bivariate analysis (P < 0.25; Figure E2). The metropolitan counties are subdivided based on the population of their metropolitan statistical area (MSA): large (central, fringe), for MSA population of 1 million or more; medium, for MSA population of 250,000–999,999; and small, for MSA population below 250,000. Non-metropolitan counties not defined as micropolitan are considered to be noncore and are thought of as the most rural areas.

Figure 4

Independent predictors of elevated allergen levels. The odds ratios from multivariable regression models are presented in the online repository (Table E4). For the independent predictors, the solid red/blue color indicates the direction of the associations (red increasing; blue decreasing) when each of the participant/housing characteristic categories were compared to the reference category adjusting for the other independent predictor variables in the model. The dashed areas indicate participant/housing characteristics included in initial prediction models based on bivariate analysis (P < 0.25; Figure E2). The metropolitan counties are subdivided based on the population of their metropolitan statistical area (MSA): large (central, fringe), for MSA population of 1 million or more; medium, for MSA population of 250,000–999,999; and small, for MSA population below 250,000. Non-metropolitan counties not defined as micropolitan are considered to be noncore and are thought of as the most rural areas.

Figure 5

Prevalence of allergen burden by census region. Allergen Burden Outcomes: Multiple Elevated Exposures (≥3 allergens at elevated levels); Multiple Detectable Exposures (≥7 allergens >LOD, ≥1 allergens at elevated levels); No Elevated Exposures (0 allergens at elevated levels); Low Exposure (≤2 allergens > LOD, 0 allergens at elevated levels). Can f 1, Fel d 1, Der f 1, and Der p 1 levels were elevated if allergen concentration >75 percentile; Alt a 1, Bla g 1, Mus m 1 and Rat n 1 levels were elevated if allergen concentration > 90 percentile. The dark background color in the map indicates statistically significant differences (P < 0.05) across census regions (Northeast, Midwest, South, West).

Figure 6

Independent predictors of allergen burden. Allergen Burden Outcomes: Multiple Elevated Exposures (≥3 allergens at elevated levels); Multiple Detectable Exposures (≥7 allergens LOD, ≥1 allergens at elevated levels); No Elevated Exposures (0 allergens at elevated levels); Low Exposure (≤2 allergens > LOD, 0 allergens at elevated levels). The odds ratios from multivariable regression models are presented in the online repository (Table E5). For the independent predictors, the solid red/blue color indicates the direction of the associations (red increasing; blue decreasing) when each of the participant/housing characteristic categories were compared to the reference category adjusting for the other independent predictor variables in the model. The dashed areas indicate participant/housing characteristics included in initial prediction models based on bivariate analysis (P < 0.25; Figure E4).