Respiratory Retention of One Micron Particles in Man

The following conclusions were reached: 1. The average retention in 110 experiments (employing 18 human subjects), using sulfobromophthalein sodium aerosol (mass median diameter equaling 1µ), was 59.6 per cent ± 13.6 per cent. Variation in retention was as low as 3 per cent to 5 per cent and as high as 25 per cent to 30 per cent in different subjects. 2. The per cent retention is not affected by the respiratory rate, tidal volume, minute volume, airborne concentration, or concentration times time.