Exposure to methylene chloride. I Its concentration in alveolar air and blood during rest and exercise and its metabolism.

Fourteen subjects were exposed to about 870 and 1,740 mg/m3 of methylene chloride in the air during rest and physical exercise on a bicycle ergometer. The duration of each exposure period was 30 min. Each subject was exposed during four periods. The concentration of methylene chloride in the alveolar air increased in the beginning but had a tendency to level off at the end of each period. There was a high correlation between the alveolar and arterial concentration of methylene chloride. The uptake of methylene chloride was about 55 % of the supplied amount at rest, about 40% at a work load of 50 W, and about 30 and 35 % at 100 and 150 W, respectively. The concentration of carboxyhemoglobin (COHb) increased both during and after exposure. With exposure to 1,740 mg/m3 a concentration of COHb in the blood of about 0.85 g/100 ml was reached. This value corresponds to about 5.5 % COHb.