EVIDENCE FOR INTERACTION BETWEEN AIR-POLLUTION AND HIGH-TEMPERATURE IN THE CAUSATION OF EXCESS MORTALITY

Studies have demonstrated repeatedly that air pollution in Athens is a ssociated with a small but statistically significant increase in morta lity. Extremely high air temperatures can also cause excess mortality. This study investigated whether air pollution and air temperature hav e synergistic effects on excess mortality in Athens. Data concerning t he increased number of deaths in July 1987 (when a major ''heat wave'' hit Greece) were compared to the deaths in July of the 6 previous yea rs. This comparison revealed a greater increase in the number of death s in Athens (97%), compared to all other urban areas (33%) and to all non-urban areas (27%). Data on the daily levels of smoke, sulfur dioxi de, and ozone; the number of deaths that occurred daily; and meteorolo gical variables were collected for a 5-y period. The daily value of Th om's discomfort index was calculated. Multiple linear regression model s were used to investigate main and interactive effects of air tempera ture and Thom's discomfort index and air pollution indices. The daily number of deaths increased by more than 40 when the mean 24-h air temp erature exceeded 30-degrees-C. The main effects of an air pollution in dex are not statistically significant, but the interaction between hig h levels of air pollution and high temperature (greater-than-or-equal- to 30-degrees-C) are statistically significant (p < .05) for sulfur di oxide and are suggestive (p < .20) for ozone and smoke. Similar result s were obtained when the discomfort index was used, instead of tempera ture in the models.