Longitudinal Evaluation of Allergen and Culturable Fungal Concentrations in Inner-City Households

Abstract

To characterize seasonal variation of three allergens (dust mite, cat, and cockroach) and total culturable fungi and to explore whether residential characteristics were associated with the concentrations of these agents, floor dust was collected from 47 inner-city homes in Minneapolis, Minnesota, over a 1-year period. A longitudinal analysis of allergen and fungal concentrations was carried out using mixed-effect models. Overall, relative humidity was a better predictor of allergen concentrations over time than indoor temperature. Seasonal variation of cat and cockroach allergens was negligible compared with the variability associated with residential characteristics such as race/ethnicity, family income, and the presence of cats. Fungal concentrations showed significant seasonal variation that outweighed the variability associated with residential characteristics. Less than 30% of the dust mite allergen and cockroach allergens concentrations were above limits of detection. Observed cockroach allergen concentrations were higher in Spanish- and Somali-speaking households than in English-speaking households, while English-speaking households had significantly higher cat allergen concentrations compared with the other language groups. The ratios of within-home to between-home variance for total culturable fungi, dust mite, cockroach, and cat allergen concentrations were 2.54, 1.91, 0.55, and 0.24, respectively. This ratio is used to predict the number of repeated measurements of each allergen required to robustly estimate long-term exposure estimates such that exposure misclassification bias is kept within acceptable limits. It is not clear whether repeated measurements of dust mite and cockroach allergens are required for long-term average exposure because of the large fraction of nondetects. It is concluded that a single measurement of cat allergen is a reasonable surrogate for long-term average exposure, since repeated measurements over time were highly correlated. Total culturable fungi will require greater than nine repeated measurements for robust assessment of long-term exposures because of low correlations in fungal measures over time.

Keywords:

• allergen
• cat
• cockroach
• dust mite
• fungi
• longitudinal study

ACKNOWLEDGMENTS

This research was supported by a Health Homes Technical Study grant from the Department of Housing and Urban Development. The authors are especially grateful to the participant families and HARS field study staff.

Notes

^AAmerican Indian, Asian, Black.

^BFour subjects did not report household income.

^ALimit of detection.

^BTotal dust samples = 254.

^CTotal dust samples from cat and no cat homes: 54 vs. 208.

^AAntilog of least squares mean using mixed-effects models with a random home effect and a fixed effect of season, after adjusting for intervention, compared to reference group (summer).

*p < 0.05.

^ARatio of the between-home variance to the sum of within- and between-home variance estimated using a mixed-effects model with a random home effect and fixed effects of intervention (no prior intervention, prior cleaning, prior education, and prior cleaning and education) and season: spring (March 20–June 20); summer (June 21–September 22); fall (September 23–December 21); winter (December 22–March 19).

^AEach mixed-effects model was adjusted for the following confounding variables: income controlled for language; housing type controlled for language, income, and presence of cat; presence of cat controlled for language, income, and housing type; temperature controlled for language, income, housing type, presence of cat, and season; relative humidity controlled for language, income, housing type, presence of cat, temperature, and season.

^BValues back-transformed to original scale.

* p ≤ 0.05.

^AValues back-transformed to original scale.

^BEach mixed-effects model was adjusted for the following confounding variables:income controlled for language; housing type controlled by language, income, and presence of cat; presence of cat controlled for language, income, and housing type; temperature controlled for language, income, housing type, presence of cat, and season; relative humidity controlled for language, income, housing type, presence of cat, temperature, and season.

* p < 0.05.

^AValues back-transformed to original scale.

^BEach mixed-effects model was adjusted for the following confounding variables:income controlled for language; housing type controlled for language and income; temperature controlled for language, income, housing type, and season; relative humidity controlled for language, income, housing type, temperature, and season.

* p <0.05.

^AValues back-transformed to original scale.

^BEach mixed-effects model was adjusted for the following confounding variables:income controlled for language; housing type controlled for language and income; temperature controlled for language, income, housing type, and season; relative humidity controlled for language, income, housing type, temperature, and season.

* p < 0.05.