862 AIR IN THE TUBES
SIR,—Studies on the homes of asthmatic children show that house cleaning increases the concentrations of dust particles of all sizes and of bacteria in the air. Moreover, a significant correlation has been found between the increase in concentration of particles 2 µm diameter and less, and reduction in respiratory mean peak flow of asthmatic children who were present during the cleaning procedures.1 Because of the rapidity of onset of changes in the respiratory function, there seems no doubt that affected patients are sensitive to small increases from high baseline values in the concentrations of these particles in the air. Human skin scales usually constitute the bulk of airborne particles in the home,2 and 1. 2.
Clark, R. P., Preston, T. D., Gordon-Nesbitt, J. Hyg. Camb. 1976, 77, 321. Clark, R. P. ibid. 1974, 72, 47.
D. C.,
of the smaller particles are macerated and fragmented skin scales. Asthmatic patients rarely suffer respiratory discomfort or asthmatic attacks on the London underground railway. This is surprising because the concentration of airborne particles in the underground system is at least ten times that in domestic houses, and contains a large percentage of human skin the size range 0.3-5.0 p.m.3 An explanation of this anomaly is suggested by the microscopic examination of the airborne particles. The figure shows stereoscan photographs of skin scales recovered from the air of the underground and of scales found in room air. The surfaces of the scales from the underground are flatter than those from room air and the edges are sharper. Under the light microscope the skin particles from the underground appear black and heavily coated. This coating is possibly of carbon from electric motors and particles from brake linings. Consequently, these skin scales, if taken into the respiratory tract, would be inert and unlikely to cause an asthmatic attack. This deposit would also cover microorganisms on the skin surface and might explain the low concentrations of bacteria-carrying particles in the air of the London underground reported by Williams and Hirch.4
some
Malka, S., Sinclair, L.
Laboratory for Aerobiology, Clinical Research Centre, Harrow, Middlesex HA1 3UJ
R. P. CLARK
COLONY ASSAY FOR PROLIFERATIVE BLAST CELLS CIRCULATING IN MYELOBLASTIC LEUKÆMIA
SIR,-Colony assays’2 have been used extensively for investigating granulopoiesis in acute myeloblastic leuksmia (A.M.L.). Abnormal growth patterns have been seen regularly,
Log-log plot of colonies formed/ml of blood venue blast cells/ml The dashed line represents the expected values for a linear relationship (slope 1 on a log-log plot).
Scanning
electron
Upper: heavily
but a correlation with morphologically recognised blast cells, the hallmark of the disease, has not been observed. We have found that a subpopulation of leukzmic blast cells form colonies
micrographs.
contaminated skin
particles
ground. Lower: skin scales recovered from
(x1285.)
m
air of London under-
3. Clark, R. P., Shirley, S. G. Nature, 1973, 246, 39. Williams, R. E. O., Hirch, A. Lancet, 1950, i, 128.
4. room air.
1. 2.
Senn, J. S., McCulloch, E. A., Till, J. E. Lancet, 1967, ii, 597. Pike, B. L., Robinson, W. A.J. Cell. Physiol. 1970, 76, 77.
SIR,—Studies on the homes of asthmatic children show that house cleaning increases the concentrations of dust particles of all sizes and of bacteria in the air. Moreover, a significant correlation has been found between the increase in concentration of particles 2 µm diameter and less, and reduction in respiratory mean peak flow of asthmatic children who were present during the cleaning procedures.1 Because of the rapidity of onset of changes in the respiratory function, there seems no doubt that affected patients are sensitive to small increases from high baseline values in the concentrations of these particles in the air. Human skin scales usually constitute the bulk of airborne particles in the home,2 and 1. 2.
Clark, R. P., Preston, T. D., Gordon-Nesbitt, J. Hyg. Camb. 1976, 77, 321. Clark, R. P. ibid. 1974, 72, 47.
D. C.,
of the smaller particles are macerated and fragmented skin scales. Asthmatic patients rarely suffer respiratory discomfort or asthmatic attacks on the London underground railway. This is surprising because the concentration of airborne particles in the underground system is at least ten times that in domestic houses, and contains a large percentage of human skin the size range 0.3-5.0 p.m.3 An explanation of this anomaly is suggested by the microscopic examination of the airborne particles. The figure shows stereoscan photographs of skin scales recovered from the air of the underground and of scales found in room air. The surfaces of the scales from the underground are flatter than those from room air and the edges are sharper. Under the light microscope the skin particles from the underground appear black and heavily coated. This coating is possibly of carbon from electric motors and particles from brake linings. Consequently, these skin scales, if taken into the respiratory tract, would be inert and unlikely to cause an asthmatic attack. This deposit would also cover microorganisms on the skin surface and might explain the low concentrations of bacteria-carrying particles in the air of the London underground reported by Williams and Hirch.4
some
Malka, S., Sinclair, L.
Laboratory for Aerobiology, Clinical Research Centre, Harrow, Middlesex HA1 3UJ
R. P. CLARK
COLONY ASSAY FOR PROLIFERATIVE BLAST CELLS CIRCULATING IN MYELOBLASTIC LEUKÆMIA
SIR,-Colony assays’2 have been used extensively for investigating granulopoiesis in acute myeloblastic leuksmia (A.M.L.). Abnormal growth patterns have been seen regularly,
Log-log plot of colonies formed/ml of blood venue blast cells/ml The dashed line represents the expected values for a linear relationship (slope 1 on a log-log plot).
Scanning
electron
Upper: heavily
but a correlation with morphologically recognised blast cells, the hallmark of the disease, has not been observed. We have found that a subpopulation of leukzmic blast cells form colonies
micrographs.
contaminated skin
particles
ground. Lower: skin scales recovered from
(x1285.)
m
air of London under-
3. Clark, R. P., Shirley, S. G. Nature, 1973, 246, 39. Williams, R. E. O., Hirch, A. Lancet, 1950, i, 128.
4. room air.
1. 2.
Senn, J. S., McCulloch, E. A., Till, J. E. Lancet, 1967, ii, 597. Pike, B. L., Robinson, W. A.J. Cell. Physiol. 1970, 76, 77.
