Data Interpretation Issues for Canada's Environmental Effects Monitoring Program

As part of Canada’s National Environmental Effects Monitoring (EEM) Program, regulated pulp and paper mills are (and metal mines will be) required to submit an interpretive report describing monitoring results. General guidance has been prepared on how to interpret these EEM data—specifically: 1) which effect endpoints to use, 2) the statistical (or other) approach to use for each endpoint to determine the presence or absence of an effect associated with exposure, and 3) the role of power analysis, α, β, and effect size in determining effects. A statistically significant difference (relative to reference conditions) in any of the effect endpoints is to be considered an exposure-associated effect for the purposes of warranting possible follow-up action. Such an effect does not, however, necessarily indicate ecological, social, or economic significance sufficient to require corrective action. Power analyses should be conducted both at the beginning of a study to determine required sampling effort and at the end of a study to determine whether the power that was actually achieved was sufficient to detect the effect size of interest. A key recommendation is to set α = β as a starting point for data interpretation. The initial recommendations of the general guidance are expected to evolve as environmental effects become better understood.