Home Endotoxin Exposure and Wheeze in Infants: Correction for Bias Due to Exposure Measurement Error

Abstract

Exposure to elevated levels of endotoxin in family-room dust was previously observed to be significantly associated with increased wheeze in the first year of life among a cohort of 404 children in the Boston, Massachusetts, metropolitan area. However, it is likely that family-room dust endotoxin was a surrogate for airborne endotoxin exposure. Therefore, a related substudy characterized the relationship between levels of airborne household endotoxin and the level of endotoxin present in house dust, in addition to identifying other significant predictors of airborne endotoxin in the home. We now reexamine the relationship between endotoxin exposure and wheeze under the assumption that the level of airborne endotoxin in the home is the exposure of interest and that the amount of endotoxin in household dust is a surrogate for this exposure. We applied a measurement error correction technique, using all available data to estimate the effect of endotoxin exposure in terms of airborne concentration and accounting for the measurement error induced by using house-dust endotoxin as a surrogate measure in the portion of the data in which airborne endotoxin could not be directly measured. After adjusting for confounding by lower respiratory infection status and race/ethnicity, endotoxin exposure was found to be significantly associated with a nearly 6-fold increase in prevalence of wheeze for a one interquartile range increase in airborne endotoxin (95% confidence interval, 1.2–26) among the 360 children in households with dust endotoxin levels between the 5th and 95th percentiles.

Does diversity of environmental microbial exposure matter for the occurrence of allergy and asthma?

“…First, it is still questionable whether reservoir measurements are a good proxy for inhalatory exposure of inhabitants of houses. 78,79 Second, environmental exposure is highly variable, 79 as observed for many exposures, including endotoxin in floor dust 80,81 and viable microbial counts. 82 The variability in the composition of the environmental microbiome raises additional problems, and together, these issues lead to different types of errors.…”

Indoor Air Contaminants and Their Impact on Respiratory Pathologies

“…22 The levels of these contaminants are very variable and can be modified according to the climatological conditions and cleanliness. The accumulation of organic material is a nutrient for fungi and bacteria; thus, wood, paper, paint and carpets can all house microorganisms.…”

Endotoxins in Indoor Air and Settled Dust in Primary Schools in a Subtropical Climate

“…and similar findings were reported in several earlier studies. 8,15,21,56 This suggests that it may be necessary to measure both airborne and settled dust endotoxin levels in order to accurately estimate indoor endotoxin exposure in school buildings.…”