Asthma research points to bacteria in household dust

• Researchers at NIEHS and the University of Iowa found a strong association between endotoxin levels and the prevalence of diagnosed asthma, asthma symptoms, asthma medication use, and wheezing.
• Endotoxins are found in the cell wall of bacteria and are only released when bacteria ruptures or disintegrates.
• Because bacteria can be found everywhere in the home, the likelihood of their release is high.
• The study, published online in the American Journal of Respiratory and Critical Care Medicine, was conducted using samples from The National Survey of Lead and Allergens in Housing (NSLAH).
• Two research assistants visited each household, administered a detailed questionnaire, conducted a home inspection, and used a standardized protocol to collect samples.
• Dust samples were collected from bedroom, kitchen and living room floors, bedding, and upholstered furniture and assayed for endotoxin.
• A disease association analysis was performed to correlate endotoxin concentrations to specific health outcomes.
• "When we analyzed the dust samples, we found that kitchen and living room floors had the highest concentrations of endotoxin," said Darryl C. Zeldin, M.D., a Senior Investigator at NIEHS.
• "However, when we looked at where the health impact of the dust was the most significant, we found that the likelihood of having recent asthma symptoms was nearly three times greater among individuals with exposure to high levels of endotoxin in the bedroom."
• Family room floors had endotoxin concentrations of 63.9 units per milligram of dust; sofas had concentration levels at 44.8; and 35.3 units on bedroom floors.
• Since the mid 1960s, researchers knew that house dust contains endotoxin, but it is only within the last five years that they began to understand the impact of household endotoxin on human health.
• Knowing what triggers asthma, whether it is endotoxins or something else, may help a physician better prevent or treat symptoms.