Importance of the personal endotoxin cloud in school-age children with asthma

Background: A number of studies have observed associations between the amount of endotoxin in urban dust and chronic asthma severity, but a direct relationship between personal exposure to household endotoxin and acute asthma worsening has not yet been defined. Objective: We sought to investigate the relationship between day-to-day changes in personal endotoxin exposure and asthma severity. Methods: In the winter and spring of 1999 through 2000, endotoxin exposures were monitored in asthmatic schoolchildren by using portable, as opposed to stationary, monitors designed to measure inhalable and respirable particulate matter less than or equal to 2.5 and 10 mu m in diameter. Children were followed with daily measurements of FEV1 and asthma symptoms. Results: Over a 24-hour period, median daily personal endotoxin exposures ranged from 0.08 EU/m(3) (measured at a particulate matter size range <= 2.5 mu m in diameter) to 0.37 EU/m(3) (measured at a particulate matter size range <= 10 mu m in diameter). Personal exposures were significantly (P <.001) higher than endotoxin measurements from either indoor or outdoor stationary monitors. Moreover, individual exposures did not correlate with stationary measurements, suggesting that exposures derived front sources in close proximity to the children's personal activities might be better correlated with disease severity. Increases in personal endotoxin exposures were associated with decreased FEV1 values and increased symptoms. Conclusions: These findings demonstrate the importance of using personal monitoring to both measure and correlate endotoxin exposure with asthma severity.