Causal association consistency

Inadequate evidence of carcinogenicity. The available studies are of insufficient quality, consistency or statistical power to permit a conclusion regarding the presence or absence of a causal association between exposure and cancer, or no data on cancer in humans are available. 

The syndrome appears to be only part of a spectrum of adverse effects associated with tryptophan (15). There has been much discussion, but finally it appears that the links are causal, as consistent findings were found in multiple independently conducted studies and the incidence of eosinophilia-myalgia syndrome in the USA fell abruptly once tryptophan-containing products were recalled (16). 

All case reports of myocarditis/pericarditis after smallpox vaccination have been carefully evaluated. It was concluded that the data are consistent with a causal relation between myocarditis/pericarditis and smallpox vaccination however, no causal association between... 

Epidemiologic studies of exposure to diesel exhaust and occurrence of lung cancer provide evidence that is consistent with a causal association. Overall, the human evidence for potential carcinogenicity for diesel exhaust is considered to be strong, but less than sufficient for diesel exhaust to be considered as a human carcinogen because of exposure uncertainties (lack of historical exposure data for exposed workers) and an inability to address all potential confounding factors. 

The subject of what evidence is necessary to conclude that an exposure is causally associated with disease has received much discussion over the years. In 1964, the seminal report to the Surgeon General on Smoking and Health [United States Department of Health, Education, and Welfare (DHEW 1964)] published criteia by which to evaluate whether an exposure was causally related to disease. These criteria were consistency, strength of association, specificity of the association, temporal relationship of the association, and coherence of the association. 

Consistency. This aspect was described as associations that are repeatedly observed by different pCTsons, in different places, circumstances, and times. HUl also stated, however, that thrae will be occasions when repetition is absent or impossible and a causal association is stiU credible. 

To obtain the mass emissions of pollutants from e-waste recycling processes, it is essential that the inputs of pollutants are truly e-waste related. To fulfill this requirement, a causal analysis is desirable. However, the concept of causation is rather problematic because causal mechanisms are complex [26]. Nonetheless, we are compelled to identify causes, in an attempt to minimize the uncertainties associated with our estimates. In this chapter, the strict empiricist, David Hume s empirical criterion, was adopted. This approach requires only a combination of (1) e-waste processing and environmental pollution are associated in space and time (contiguity) (2) e-waste processing precede to environmental pollution (temporal succession) and (3) e-waste processing is always conjoined with environmental pollution (consistent conjunction). These are always the cases judged from a number of previous studies [6, 27-35]. 

In humans methylene chloride exposure has been associated with a wide variety of cancers in a number of cohort and case control studies pancreatic, prostate, lung, liver, cervical, breast, and astrocytic brain tumors have been reported. Limitations in these studies include small sample size, incomplete exposure information, and concomitant exposure to other carcinogenic substances. The lARC has stated that there is not a sufficiently consistent elevation of risk across studies to make a causal interpretation credible. In a recent study of 1473 workers, followed for nearly 50 years, methylene chloride exposure level was not related to mortality due to all causes, malignant neoplasms, or lung and pancreatic cancers. ... 

The IOM committees are much clearer about what they don t do than about what they do do. The 2000 Update says Consistent with the mandate of P.L. 102-4, the distinctions between categories are based on statistical association, not on causality, as is common in scientific reviews. Thus, standard criteria used in epidemiology for assessing causality [reference omitted] do not strictly apply. 54 It leaves unsaid what criteria do apply. 55... 

Except for suicidality, the medication guide does not specifically state that there is a causal link between this list of reactions and the medications but clearly implies that these reactions are associated with taking medication. Each symptom is consistent with the activation or stimulation syndrome. The inclusion of anger, aggression, and violence shows the FDA s well-justified concern about antidepressants posing a serious danger to others. 

In a German hospital specializing in Chinese herbalism of 145 patients who had been treated within 1 year 53% reported having had at least one adverse effect attributable to Chinese herbal medicines (107). Nausea, vomiting, and diarrhea were the most common complaints. It should be noted that causality in these cases can only be suspected and not proven. In the same institution about 1 % of 1507 consecutive patients treated with Chinese herbal mixtures had clinically relevant rises in liver enzymes (108,109). Glycyrrhiza radix and Atractylodis macro-cephalae rhizome were most consistently associated with such problems. In most of these cases there were no associated clinical signs and the abnormalities tended to normalize without specific therapy and in spite of continued treatment with the Chinese herbal mixtures. 

Criteria similar to those listed by Adams (2003) are used to establish causality and are derivatives of Koch s postulates and Hume s criteria. The list includes (1) strength of association, (2) consistency of association, (3) specificity of association, (4) time order or temporality, (5) biological gradient over space and time, (6) experimental evidence available, and (7) biological plausibility. In many instances, especially at a regional scale and over long periods of time, meeting the requirements for each of these criteria can be difficult. 

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