Daily respiratory mortality and PM10 pollution in Mexico City: importance of considering place of death

Significant associations have been reported between particles,vith a 50% cu t-off aerodynamic diameter of 10 mm (PM10) and ozone ambient concentrations , and daily number of deaths from respiratory causes. The aim of the presen t study was to assess such associations among elderly (greater than or equa l to 65 yrs) residents of Mexico City. Ambient air pollution data were provided by the Metropolitan Monitoring Net work. During the study period, the average daily PM10 ranged 23.4-175.3 mu g.m(-3), and ozone 1 h daily maximums ranged 39.4-216.7 ppb. Information wa s compiled on the primary and underlying causes of death. The analyses were conducted separately according to place of death (within or out of a hospi tal unit) using time-series methodology. The total number of deaths from all respiratory causes and mortality for ch ronic obstructive pulmonary diseases (COPD) were significantly related to P M10 over different lags: an increase of 10 mu g.m(-3) was related to a 2.9% (95% (CT): 0.9-4.9%) increase and to a 4.1% (95% CI: 1.3%-6.9%) increase w ith a S-day lag when death occurred out of medical units, respectively. For deaths occurring in medical units, a longer lag and smaller risk estimate was observed. An interactive effect between PM10 and ozone was detected. This study confirms that there is an important impact of PM10 on respirator y morbidity among elderly subjects. It also indicates that accounting for p rimary and underlying causes of death, and considering place of death may r educe misclassification and provide more accurate estimates of the adverse impact of PM10 on mortality.