Predictors of airborne endotoxin in the home

We identified home characteristics associated with the level of airborne en dotoxin in 111 Boston-area homes enrolled in a cohort study of home exposur es and childhood asthma, and we developed a predictive model to estimate ai rborne endotoxin. We measured endotoxin in family-room air and in dust from the baby's bed, family room, bedroom, and kitchen floor. Level of airborne endotoxin was weakly correlated (r < 0.3) with level of endotoxin in each of the four types of dust samples and was significantly correlated with end otoxin in family-room dust (p < 0.05). Endotoxin in family-room dust accoun ted for < 6% of the variability of airborne endotoxin. In a multivariate mo del, certain home characteristics were positively (p < 0.05) associated wit h airborne endotoxin. These included current presence of dog (difference in level, dog vs. no dog = 72%, partial R-2 = 12.8%), past presence of dog (p artial R-2 = 5.5%), and endotoxin level in family-room dust (partial R-2 = 5.3%). Use of a dehumidifier (partial R-2 = 6.4%) was negatively associated (p = 0.02; difference = -31%) with airborne endotoxin. Other home characte ristics were identified as important determinants of increased airborne end otoxin in this model, but individual coefficients were not statistically si gnificant (alpha = 0.05): total amount of fine dust collected in the home ( partial R-2 = 3.8%), concrete floor in family room (3.7%), water damage (3. 6%), and use of cool-mist humidifier in past year (2.7%). This multivariate model explained 42% of the variability of airborne endotoxin levels, a sub stantial improvement over that with dust endotoxin alone. Airborne endotoxi n in Boston-area homes appears to be determined by the presence of dogs, mo isture sources, and increased a-mounts of settled dust.