Associations between short-term changes in nitrogen dioxide and mortality in Canadian cities

The association between daily variations in ambient concentrations of nitrogen dioxide (NO2) and mortality was examined in 12 of Canada's largest cities, using a 19-yr time-series analysis (from 1981-1999). The authors employed parametric statistical methods that are not subject to the recently discovered convergence and error estimation problems of generalized additive models. An increase in the 3-d moving average of NO2 concentrations equivalent to the population-weighted study mean of 22.4 ppb was associated with a 2.25% (t = 4.45) increase in the daily nonaccidental mortality rate and was insensitive to adjustment for ozone, sulfur dioxide, carbon monoxide, coefficient of haze, size-fractionated particulate mass, and the sulfate ion measured on an every-6th-day sampling schedule. The 3-d moving average of NO2 was sensitive to adjustment for fine particulate matter measured daily during the 1998-2000 time period.