AIR-POLLUTION AND DAILY MORTALITY IN LONDON - 1987-92

Objective-To investigate whether outdoor air pollution levels in Londo n influence daily mortality. Design-Poisson regression analysis of dai ly counts of deaths, with adjustment for effects of secular trend, sea sonal and other cyclical factors, day of the week, holidays, influenza epidemic, temperature, humidity, and autocorrelation, from April 1987 to March 1992. Pollution variables were particles (black smoke), sulp hur dioxide, ozone, and nitrogen dioxide, lagged 0-3 days. Setting-Gre ater London. Outcome measures-Relative risk of death from all causes ( excluding accidents), respiratory disease, and cardiovascular disease. Results-Ozone levels (same day) were associated with a significant in crease in all cause cardiovascular, and respiratory mortality; the eff ects were greater in the warm season (April to September) and were ind ependent of the effects of other pollutants. In the warm season an inc rease of the eight hour ozone concentration from the 10th to the 90th centile of the seasonal range (7-36 ppb) was associated with an increa se of 3.5% (95% confidence interval 1.7 to 5.3), 3.6% (1.04 to 6.1), a nd 5.4% (0.4 to 10.7) in all cause, cardiovascular, and respiratory mo rtality respectively. Black smoke concentrations on the previous day w ere significantly associated with all cause mortality, and this effect was also greater in the warm season and was independent of the effect s of other pollutants. For black smoke an increase from the 10th to 90 th centile in the warm season (7-19 mu g/m(3)) was associated with an increase of 2.5% (0.9 to 4.1) in all cause mortality. Significant but smaller and less consistent effects were also observed for nitrogen di oxide and sulphur dioxide. Conclusion-Daily variations in air pollutio n within the range currently occurring in London may have an adverse e ffect on daily mortality.