Air pollution exposure monitoring and estimation Part III. Development of new types of air quality indicators

The temporal pattern of exposure to a specific compound may affect health i n several ways. Exposure to pollution can have short-term effects or long-t erm effects. For some compounds there is a threshold under which there is n o presumed measurable effect, whereas for other compounds, there is no pres umed threshold. For short-term effects, the exposure to a high concentratio n of a compound one day may either increase or decrease the response if val ues of the same compound become high again the next day. Adaptation to effe cts of short-term exposure to ozone, for example, is reported. Similarly, h ealth response to sudden high peaks of concentration may also possibly diff er in effect from those to peaks attained more gradually. For long-term eff ects of some compounds, the cumulative exposure may be more decisive in inf luencing health. This paper proposes and describes in detail several air qu ality indicators that reflect the time variability and the episodic nature of air pollution exposure, as an attempt to represent the temporal aspects of pollution exposure that may have important effects on health. Mean conce ntrations, 98th percentile and maximum values are the traditional indicator s for estimating exposure. The temporal variability of particulate matter ( PM10) and NO2, however, is here described by means of: (1) the rate of chan ge of pollution as the difference between two consecutive hourly or daily v alues, and of (2) episodes, described in terms of number, duration and inte r-episode period, maximum concentration in the episode, and integrated epis ode exposure.