title: Within-home versus between-home variability of house dust endotoxin in a birth cohort.
abstract: Endotoxin exposure has been proposed as an environmental determinant of allergen responses in children. To better understand the implications of using a single measurement of house dust endotoxin to characterize exposure in the first year of life, we evaluated room-specific within-home and between-home variability in dust endotoxin obtained from 470 households in Boston, Massachusetts. Homes were sampled up to two times over 5-11 months. We analyzed 1,287 dust samples from the kitchen, family room, and baby's bedroom for endotoxin. We fit a mixed-effects model to estimate mean levels and the variation of endotoxin between homes, between rooms, and between sampling times. Endotoxin ranged from 2 to 1,945 units per milligram of dust. Levels were highest during summer and lowest in the winter. Mean endotoxin levels varied significantly from room to room. Cross-sectionally, endotoxin was moderately correlated between family room and bedroom floor (r = 0.30), between family room and kitchen (r = 0.32), and between kitchen and bedroom (r = 0.42). Adjusting for season, the correlation of endotoxin levels within homes over time was 0.65 for both the bedroom and kitchen and 0.54 for the family room. The temporal within-home variance of endotoxin was lowest for bedroom floor samples and highest for kitchen samples. Between-home variance was lowest in the family room and highest for kitchen samples. Adjusting for season, within-home variation was less than between-home variation for all three rooms. These results suggest that room-to-room and home-to-home differences in endotoxin influence the total variability more than factors affecting endotoxin levels within a room over time.
authors.affiliation: Harvard School of Public Health, Boston, Massachusetts, USA.
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Abraham
authors.forename: Diane R
authors.initials: DR
authors.lastname: Gold
authors.forename: Douglas W
authors.initials: DW
authors.lastname: Dockery
authors.forename: Louise
authors.initials: L
authors.lastname: Ryan
authors.forename: Ju-Hyeong
authors.initials: JH
authors.lastname: Park
authors.forename: Donald K
authors.initials: DK
authors.lastname: Milton
mesh_terms: D000393:Air Pollutants; D016902:Air Pollution, Indoor; D001900:Boston; D015331:Cohort Studies; D004391:Dust / Q000032:analysis*; D004731:Endotoxins / Q000032:analysis*; D004784:Environmental Monitoring / Q000379:methods / Q000706:statistics & numerical data*; D006090:Gram-Negative Bacteria / Q000378:metabolism; D006798:Housing; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008033:Limulus Test
chemical_list: D000393:Air Pollutants; D004391:Dust; D004731:Endotoxins