Smoking in small places: separation is the only solution. (Science Selections).

Increased smoking rates in many European countries bring with them a growing concern about indoor air quality. Without question, sidestream environmental tobacco smoke (sETS) from the tip of a burning cigarette immediately impacts the senses and causes discomfort; at the same time, perceptual and comfort aspects are growing in importance among indoor air quality regulators. Yet quantitative thresholds for odor and eye, nose, and throat irritation from sETS have not been conclusively determined.

New research by Martin H. Junker and colleagues from the Federal Institute of Technology in Zurich, Switzerland, indicates that odor thresholds for sidestream smoke and thresholds for eye, nose, and throat irritation are much lower than previously reported--300 times lower for odor thresholds and about 10 times lower for nasal and eye irritation [EHP 109:1045-1052]. Notably, the highest concentration of sidestream smoke to which subjects were exposed was equivalent to one cigarette being smoked in a room with a volume of 100 cubic meters, the size of a spacious European living room. This study is the first controlled laboratory experiment to consider sensory symptoms at such low concentrations of sETS.

To measure the sensory impact of indoor secondhand smoke, investigators exposed 24 healthy female nonsmokers aged 18-35 to varying concentrations of sETS. The toxic components of sETS were continuously monitored, and included particle-bound polycyclic aromatic hydrocarbons, total volatile organic compounds, particle number concentrations, and carbon monoxide.

In an initial olfactory experiment, the researchers had 18 subjects place their noses into an olfactometer. When smoke from passively burning cigarettes was introduced in varying concentrations, subjects indicated when they were able to detect its presence.

In a second experiment, 24 subjects were seated in an exposure chamber into which varying concentrations of cigarette smoke were added to the airflow. At each concentration level, breathing patterns and startle reflexes were measured. At each level, subjects scaled their perceptions of odor strength; eye, nose, and throat irritation; arousal; annoyance; odor perception; and judgment of air quality. The investigators then plotted increases in the intensity of symptoms against relative increases in the concentration of smoke.

Results showed that even at the lowest sETS concentrations, the subjects perceived a significant increase in eye, nose, and throat irritation. They also felt considerably more annoyed, and the quality of air was reported to be less acceptable compared with air not polluted by sETS. At the highest sETS exposure, the startle reflex amplitude was reduced. The authors interpreted this finding as indicative of distracted attention.

The researchers found that to protect against eye and nasal irritations, the volume of fresh air needed to dilute the smoke from a single cigarette would be more than 3,000 cubic meters. To ensure acceptable indoor air quality, the sidestream smoke of one cigarette would have to be diluted by an estimated fresh air volume of 19,000 cubic meters. This is at least 100 times the volume other researchers have proposed.

The sensory thresholds are so low, the researchers observed, that protecting indoor air quality would require ventilation rates that are impractical and economically ruinous. They conclude that effectively protecting nonsmokers requires separately ventilated areas or a complete ban on smoking.