In order to determine causality, a combination of tests and approaches must be used, including toxicity assessment, chemical analysis, biomarkers and exposure assessment. Usually these samples are taken from the environment back to a laboratory for testing. By doing a toxicity assessment, it is possible to identify impacts on aquatic life in the receiving systems and assess toxicity. Therefore, it provides some qualitative information. However, it cannot provide quantitative comparisons to other mill effluents or sites.
Chemical analysis involves the measure of the concentration of specific compounds.
By itself, this test does not give any indication of the potential toxic impacts of complex mixtures, so in this respect, toxicity testing is much more important. However, chemical analysis is specific to a sample site so that zones of toxic conditions can be identified, therefore leading to assessment maps. They are also established under the rules of quality assurance and quality control and are therefore repeatable tests. Usually, they are identified as either biochemical, morphological or physiological responses to chemical contaminant stress. They have been identified as being most useful when traditional assessment endpoints, like reproduction, growth or survival, or population and community responses, are pertinent to their biological significance.