Comparison of endotoxin exposure assessment by bioaerosol impinger and filter-sampling methods

Environmental assessment data collected in two prior occupational hygiene s tudies of swine barns and sawmills allowed the comparison of concurrent, tr iplicate, side-by-side endotoxin measurements using air sampling filters an d bioaerosol impingers. Endotoxin concentrations in impinger solutions and filter eluates were assayed using the Limulus amebocyte lysate assay, In sa wmills, impinger sampling yielded significantly higher endotoxin concentrat ion measurements and lower variances than filter sampling with IOM inhalabl e dust samplers. Analysis of variance for repeated measures showed that thi s association remained after controlling for other factors such as replicat e, sawmill, sawmill operation, wood type, and interaction terms. Endotoxin concentrations in the swine barns were 10-fold higher on average than in sa wmills. These samples demonstrated comparable endotoxin concentration estim ates for impinger and filter methods although the variability was Lower usi ng the impinger method. In both occupational settings, side-by-side replica tes were more uniform for the impinger samples than for the filter samples. This study demonstrates that impinger sampling is an acceptable method for quantitation of area endotoxin concentrations, Further, when sampling is p erformed with impingers for airborne microorganism quantitation, these same impinger solutions can yield valid endotoxin exposure estimates, negating the need for additional filter sampling.