Linear regression is suitable to use when a time series data suggest a simple linear increasing or decreasing trend on a plot of data against time \cite{Gilbert_1988}. The overall idea of regression is first to examine whether a set of predictor variables (criteria pollutants) is good enough to predict an outcome (risk of acute myocardial infarction) and secondly, to identify which of the variables are significant predictors of the outcome variable. Also, regression examines in what way in terms of magnitude does the predictor variables impact the outcome variable \cite{statisticssolutions2013}.