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Characteristics of Causal Relationships Supported by Different 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. Notice that the first set (Table 5-3) is based solely on evidence from the impaired site and associated reference 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.

Table 5-3. Characteristics of Causal Relationships Supported by Types of Evidence that Use Data from the Case
Type of EvidenceCharacteristic of Causal Relationships
Spatial/Temporal Co-occurrence Co-occurrence
Evidence of Exposure or Biological Mechanism Co-occurrence
Causal Pathway Co-occurrence
Stressor-Response Relationships from the Field Co-occurrence
Sufficiency
Manipulation of Exposure Manipulation
Temporality
Co-occurrence
Coherence
Sufficiency
Laboratory Tests of Site Media Manipulation
Sufficiency
Temporal Sequence Temporality
Verified Prediction Manipulation
Temporality
Co-occurrence
Coherence
Sufficiency
Symptoms Coherence
Sufficiency
Table 5-4. Characteristics of Causal Relationships Supported by Types of Evidence that Use Data from Elsewhere
Type of EvidenceCharacteristic of Causal Relationships
Stressor-Response Relationships from Other Field Studies Sufficiency
Stressor-Response Relationships from Laboratory Studies Manipulation
Sufficiency
Stressor-Response Relationships from Ecological Simulation Models Sufficiency
Mechanistically Plausible Cause Coherence
Manipulation of Exposure at Other Sites Manipulation
Coherence
Sufficiency
Analogous Stressors Coherence
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