환경소송에서 원인물질과 손해 사이의 인과관계가 불분명한 경우 피해자의 구제 방법: 원자력발전소 인근 주민의 갑상선암 발병 사건을 중심으로

This study analyzes legal remedies for victims in environmental litigation exemplified by thyroid cancer cases involving residents near nuclear power plants in case of causal uncertainty between causative agent and damage from a law and economics perspective. From the standpoint of internalization of externalities and achieving allocative efficiency, courts adjudicating the elements of liability should aim to minimize the total social costs associated with torts by incentivizing actors to adopt socially optimal levels of precaution. In a similar vein, within the context of special tort cases such as environmental litigation, courts engage in a process of normative optimization regarding the burden of proof. This involves determining whether to depart from the traditional principle of Substantial Factor Test in favor of alternative evidentiary theories, such as probabilistic causation, the theory of de facto presumption (indirect counter-proof), presumption of causation, and epidemiological causation. In this context, unlike direct infringements of property rights which generally constitute per se illegality, the doctrine of the tolerability has been adopted for harmful externalities such as environmental pollution, reflecting the reciprocal nature of externalities. Recently, Korean courts appear to be placing increasing reliance on regulatory standards established under public law as a primary criterion for determining this tolerability. According to the Coase theorem, the court determines what the final state of resource allocation would have been if the transaction costs were sufficiently low and the voluntary transactions and negotiations between the parties were sufficiently advanced, and declares that the rights will be allocated accordingly. From this perspective, it can be understood that the regulatory standards of public law play a role in adjusting the incentive system for market participants so that the efficiency of resource allocation can be achieved in the private law domain. In the backdrop of the above-mentioned law and economics theory, this paper examines the US public law regulatory standards and precedents regarding causation in relation to the cases of thyroid cancer in residents near nuclear power plants. First, with regard to regulatory standards under public law, United States believes that the dose-constraint of 0.1 mSv and 0.15 mSv per year set forth in U.S.NRC 10CFR50 Appendix I is not a “regulatory standard of public law” for determining whether the defendant's actions were illegal and caused damages to the plaintiff, whereas the Linear Non-Threshold Theory (LNT), which is the basis for 10CFR20, is considered to be a “regulatory standard of public law” as a requirement for dose limits for the general public. Next, with regard to causation, the U.S. has ruled that a causation must be recognized if the relative risk is at least 2.0, and some state courts have ruled that if the relative risk is less than 2.0, it is a counter-evidence (“disproves”) not to recognize the causation. In some cases, if the relative risk is found to exceed 2.0, it is considered that the preponderance of evidence has been achieved to establish a causation. However, in the case of Korea, not only is the relative risk (exceeding 2.0) quite high, but it is also necessary to prove that the risk factor is likely to have caused the non-specific disease to establish a high likelihood of a causation. The standards of proof for determining causation in radiation tort litigation in Korea and United States are quite different. This is likely because Korea has adopted the standard of proof of “highly likelihood”, while United States has adopted the standard of proof of “preponderance of evidence”. Issues such as the recognition of epidemiological causation and the recognition of a causation in terms of relative risk are ultimately a process of internalizing external effects through tort litigation and normative optimization to remedy environmental damage. It is necessary to make a normative assessment of whether the results of lawsuits for torts through the principle of substantial factor test, probabilistic causation, the theory of de facto presumption (indirect counter-proof) are leading to systematic undercompensation from the perspective of internalization of external effects and relief for victims, and whether the recognition of epidemiological causation considering relative risk will lead to systematic overcompensation. Of course, in the process of such normative evaluation, consideration should also be given to how successfully other institutional mechanisms that can remedy environmental damage and internalize externalities are working, in addition to tort litigation in court.