§ Lord O'HAGANasked Her Majesty's Government:
How much airborne lead is absorbed by the human body.
§ Lord WELLS-PESTELLI am advised that the amount of airborne lead deposited in the lung and the amount exhaled depends upon a combination of two factors: the size distribution of the inhaled particles and the breathing pattern.
A considerable amount of research work has shown that the rate of breathing and the volume of air inhaled with each breath affect deposition and that this relationship varies over a wide range. More recent experiments show that under a wide range of conditions the amount of airborne lead particles deposited in the lung varies from 15 per cent. at a breathing rate of 15 breaths per minute and a breath volume of 1 litre, up to 42 per cent. at 4 breaths per minute and a breath volume of 1.7 litres.
Lead does not accumulate in the lung and it is therefore assumed that most passes through the lung wall and is taken up by the blood stream. In the blood, lead becomes attached to red cells and thereafter is gradually excreted, half of the lead in the blood being removed in 15–20 days. Airborne lead can also be deposited on food and absorbed via the intestinal tract. However, the amount involved is extremely small.