Linear causation

Expediency, linked together with a linear causation model, thus restricts many investigations [2], It has been further noted [7] that by narrowing down the possible combination of substandard acts and specific situations to a single stage, the identihcation and control of contributing causes has been severely limited [2],... 

Heinrich s approach is to identify, evaluate, and work on the middle dominoes, not just the last one or two dominoes in the line. The domino theory has significant limitations. The basic assumption is that there is a linear relationship between causation and progression. In other words, one occurrence follows another and ends in an incident. In the context of process-related incidents, this assumption is not always valid. Often parallel occurrences coincide to result in an incident rather than occurring as purely sequential occurrences. Nevertheless, the domino theory can provide a useful conceptual framework for simple incidents. 

In contrast, radiation protection policy (ICRP 2008) benefits from an assumption of linearity as a tool to attribute causation in an equitable way. Linear dose-response relationships could also serve a useful purpose for chemical safety, with the following qualifications ... 

Judicial decisions in nonregulatory contexts such as toxic tort and product liability suits are likewise inconsistent in their consideration of the linear, no threshold model. As in the regulatory context, most cases find no problem with an expert s reliance on a risk assessment using the linear model. In a handful of cases, however, the court rejects reliance on a linear dose-response assumption. Eor example, one court in addressing the cancer risks from a low concentration of benzene in Perrier held that there is no scientific evidence that the linear no-safe threshold analysis is an acceptable scientific technique used by experts in determining causation in an individual instance (Sutera 1997). Another court decision concluded that [t]he linear non-threshold model cannot be falsified, nor can it be validated. To the extent that it has been subjected to peer review and publication, it has been rejected by the overwhelming majority of the scientific community. It has no known or potential rate of error. It is merely an hypothesis (Whiting 1995). The inconsistency and unpredictability of judicial review of risk assessments adds an additional element of uncertainty into the risk assessment process. 

This chapter deals with correcting the use of conjectures as defaults in regulatory policy, in the context of experimental evidence of hormesis and causation and alternative probabilistic cancer models. Specifically, we summarize how the combination of mode-of-action and weight-of-evidence supports both J-shaped and U-shaped, rather than the linear, no-threshold (LNT) models. The EPA uses the terms nonlinear for the threshold model and low-dose-linear for the LNT models (meaning that the slope is greater than zero at zero dose), which is well-approximated by a straight line, at very low doses and beginning from zero dose (EPA 2005). 

Here r=-0.8569. This suggests a strong correlation equation (5.3) gives t = 3.33, well above the critical value (P = 0.05) of 2.78. But (a) a non-linear relationship is more likely, and (b) correlation is not causation - the Hg contamination may arise elsewhere. 

According to [3] an essential part of the accident causes were human failures. But everything the [plant] operators did they did consciously and apparently with complete conviction that they were acting properly . [4] explains The plant operators, [...] however, thought in terms of linear networks of causation rather than considering potential side effects of their decisions and actions . To handle these kinds of problems the consideration of safety regulations is absolute necessary. The human errors of Chernobyl were the consequences of the contempt of safety related regulations. 

This distinction between facts and interpretations is not always made in the causal sequence models of accidents. Such linear accident causation models as the ILCI model do not make a clear distinction between observable facts and conditions on the one hand and opinions about effects of personal and... 

---