exposure to microbial products, especially endotoxin, may have an impact on vulnerability to allergic diseases. the following are data on concentration (eu/mg) in settled dust for one sample of urban homes and another of farm homes. u: 6.0 5.0 11.0 33.0 4.0 5.0 80.0 18.0 35.0 17.0 23.0 f: 3.0 12.0 13.0 8.0 6.0 8.0 4.0 18.0 6.0 9.4 21.0 9.1 1.0 1.0 0.6