Causal Characteristics and Types of Evidence

The types of evidence and the characteristic of causation that they can represent are presented in Tables 5-3 and 5-4. Some types of evidence can support more than one characteristic, depending on how the study is designed.

The first set (Table 5-3) is based solely on evidence from the impaired site and associated comparison sites (i.e., sites that are part of the case). The second set (Table 5-4) uses knowledge gained from other studies to show that conditions at the impaired site could reasonably be expected to result in specific biological effects. Therefore, evidence for temporality and co-occurrence come only from the site. Evidence for coherence and sufficiency are more likely to come from other field and laboratory studies. Used together they make a stronger case that can help us identify probable causes of impairment in our environment.