The nature of the smoke. Factors affecting exposure and the assessment of exposure. The report considers sensitive populations such as children, pregnant women, older persons, and those with persisting respira- tory illnesses. ETS gen- erated by other people. However, a pregnant, nonsmoking woman might be affected by exposure to ETS, as may her fetus.
Some attention is paid to irritation, annoyance, and associated responses.
These various components are re- leased into the environment and are diluted by ambient air. The percent of the population who smoke steadily increased over the first two-thirds of this century but has declined more recently. Table 1-1 gives cigarette consumption since 1900. The actual probability of exposure to ETS is complex, affected by ventilation rates, size of houses, restrictions on where tobacco products may be smoked, and changes in the cigarette itself. The consequence of Figure 1-1 is that the general probability of being exposed to some ETS for the nonsmoker has increased until quite recently.