Analysis of trends in tropospheric ozone in the Lower Fraser Valley, British Columbia

A method of trend detection for high quantiles of a pollutant such as ozone is presented and applied to 1978–1990 data from two stations downwind of the city of Vancouver in the Lower Fraser Valley, British Columbia. Theories of order restricted inference and isotonic regression are used for the method. The new statistical methodologies in this article are (a) the use of the chi-square bar statistic from order restricted inference for estimators that are asymptotically normal and (b) a method for obtaining standard errors for estimators from (pollutant) data that are serially correlated. Our analysis uncovers opposite trends in pollution data at the two stations. We interpret these trends as due to recent changes in population distribution in the Lower Fraser Valley.