Pollution of delivery ward air by nitrous oxide--methoxyflurane.

Pollution of delivery ward atmosphere by analgesic gases and vapors has not been studied as extensively as pollution of operating theaters. This study shows that delivery room atmosphere is polluted by methoxyflurane (0.5--0.8 ppm) and nitrous oxide (300--540 ppm) and that a local gas exhaust system reduces the concentration by half.

Exposure to xylene and ethylbenzene. I. Uptake, distribution and elimination in man.

Industrial xylene is a mixture of xylene and ethylbenzene. Twelve male subjects were exposed to industrial xylene in inspired air, six subjects in series I to 870 mg/m3 at rest (30 min) and light exercise on a bicycle ergometer (90 min) and six subjects in series II to 435 mg/m3 at rest (30 min) and during exercise of increasing work loads (90 min). The measurements of xylene uptake were performed continuously with the Douglas bag technique. In both series, about 60% of the amount of xylene supplied to the lungs was taken up. In both series, the concentration in alveolar air was relatively low throughout the entire exposure. The relative concentration in alveolar air displayed a linear correlation to the percentage uptake in the lungs. The ratio between the concentration in arterial blood (mg/kg) and alveolar air (mg/l) amounted to 30--40 at the different work loads. The total amount of xylene expired after the exposure was estimated from the alveolar concentration and alveolar ventilation. In series I, with a total uptake of 1.4 g, the subjects expired about 70 mg, i.e., about 5%. The corresponding value in series II was 40 mg of a total uptake of 1.0 g, i.e., about 4%.

Exposure to trichloroethylene I. Uptake and distribution in man.

Fifteen healthy male subjects were exposed to about 540 and 1,080 mg/m3 of trichloroethylene (TRI) in the air during rest and exercise on a bicycle ergometer. Each subject was exposed during four 30-min periods. The arterial blood concentration increased linearly with the concentration in the alveolar air. The uptake of TRI was about 55% of the supplied amount at rest. At a work load of 150 W during the fourth period the percentage uptake decreased to about 25%. For one fairly thin subject the uptake was near zero at the end of exposure. This development was probably due to the relatively low solubility of TRI in blood and tissues. The uptake of TRI may be estimated from pulmonary ventilation and the concentration in alveolar and inspiratory air.

Exposure to butyl alcohol: uptake and distribution in man.

Twelve subjects were exposed to 300 or 600 mg/m3 of butyl alcohol in inspired air during rest and during exercise on a bicycle ergometer. Exposure lasted 2 h. The results were puzzling in view of the high blood/air partition coefficient for butyl alcohol. The arterial blood concentration was low. The concentration in the last part of the expired air, i.e., the ""alveolar'' concentration, was low. The quotient of ""alveolar'' concentration X 100/inspired concentration was low in relation to the low percentage uptake. However the high solubility of butyl alcohol in water may explain the results. Butyl alcohol was probably partially taken up in the water of the dead space mucous membranes during inspiration. It was then partially released from the membranes. Therefore the concentration of butyl alcohol in the last part of expiration was probably not the same as the concentration in the alveolar air.

Exposure to anesthetic gases and ethanol during work in operating rooms.

The concentration of halothane and ethanol in operating rooms was measured during 37 routine operations performed in nine different departments of surgery at six different hospitals. The time-weighted halothane concentrations in the respiratory zones of anesthetic and surgical nurses were 0.3--34.0 ppm (time-weighted average 7.2 ppm) and 0.1--9.2 ppm (time-weighted average 2.5 ppm), respectively, in the different operating departments. The corresponding ethanol concentrations were 0.3--36.5 ppm (time-weighted average 12.5 ppm) for anesthetic nurses and 1.5--46.6 ppm (time-weighted average 15.3 ppm) for surgical nurses. The anesthetic technique influences the exposure of the operating staff to anesthetic gases, but it does not affect exposure to ethanol. In controlled experiments volunteers were exposed to low concentrations of halothane or ethanol. About 60% of both substances was retained. The content of ethanol in the end-expired air approached zero within a few minutes after the end of exposure, while low residual concentrations of halothane were demonstrable for more than 1 h. Although exposure to ethanol is insignificant in relation to the metabolic capacity of the body, ethanol indicates the presence of volatile disinfectant components, and its spread through the room atmosphere should be kept in mind when the ventilation of operating rooms is designed. The effective elimination of airborne pollutants in operating rooms calls for good general ventilation in conjunction with local exhaust close to the sources of anesthetic gas leakage. General ventilation mainly affects the concentration of substances well-mixed with the room atmosphere, such as volatile disinfectant components and anesthetic vapor that has spread beyond the actual work zones of the medical staff. For a significant reduction in the concentration of anesthetic gases in the respiratory zones of the medical staff, the gases must be vented at the source of leakage. Since airborne anesthetics occur not only in operating rooms, general ventilation has to meet certain minimum requirements also in anesthetic induction rooms and recovery rooms. Operating rooms and anesthetic induction rooms must also be supplied with local exhaust systems.

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.

Exposure to white spirit. I. Concentration in alveolar air and blood during rest and exercise.

Fifteen healthy male subjects were exposed to 1,250 and 2,500 mg/m3 of white spirit in inspiratory air during rest and excercise on a bicycle ergometer. The white spirit contained approximately 83% aliphatic and 17% aromatic components. The duration of each exposure period was 30 minutes. The pulmonary ventilation, the cardiac output, and the concentration of white spirit (subdivided into aromatic and aliphatic components) in alveolar air, arterial blood, and venous blood were determined during and after exposure. The concentration of aliphatic and aromatic components in alveolar air tended to level off towards the close of each period. The resting level of the aromatic components increased approximately 2.0 times, and that of aliphatic components about 2.5 times, during exercise with increased intensities. The concentration of aliphatic components in arterial and venous blood increased at the start of each exposure period but tended to level off towards the close of the period. The resting value increased fourfold in work at the highest intensity. However, the concentration of aromatic components rose sharply during each period. The arterial blood concentration was about 15 times higher at the end of exposure during the heaviest exercise intensity than at rest. Pulmonary ventilation appeared to be more important to uptake in arterial blood than to circulation. The results are believed to be due to the differing solubilities of aliphatic and aromatic components in blood. Measurement of the concentration of white spirit in venous or arterial capillary blood is suggested as a biological check on exposure.