环境诉讼成为一种新型的诉讼类型具有深刻的社会背景。人与自然关系的变化是人类环境意识的觉醒的表现，环境权概念的清晰化、环境侵权的社会现实和法律的进步发展是环境诉讼兴起的重要原因。环境诉讼与其他诉讼相比，有其自身的特征，主要表现为环境诉讼中的当事人力量不对等，判决结果涉及多重利益，和证明的困难。这种证明的困难不仅表现在侵害行为和损害结果上，环境诉讼中因果关系的认定涉及立法、司法政策和科学技术等多方面的因素，比一般诉讼更为复杂。采用何种因果关系理论和证明方法是环境诉讼必须要解决的理论与实践难题。因果关系理论受哲学的影响，在法学领域内也是一个令人学者痴迷和兴奋的话题。两大法系在侵权法上发展形成了多种因果关系的理论学说，以指导实践。量子力学的发展突破了经典力学的理论，决定论的因果关系逐渐被非决定论的因果关系概念所替代。而运用概率和统计归纳的理论去解决实践中法律因果关系判断问题是现代型诉讼的内在要求。相当因果关系理论的提出恰好可以为这种需求解决理论基础。统计证据是概率统计学理论在法律证明中的重要表现，统计证据就是利用科学的统计学的概率原理来进行科学证明的证据，其本质上就是表明数据说明了什么。统计证据的概念体现在法律可能性当中，要求一个仅观察随机变量的概率模型并包含有效的、明确的和客观的衡量证据强度的方法以及提供明确客观的手段控制误导性和削弱证据的概率。统计证据在诉讼中有两种表现形式：一种直接用数据统计的概率结果证明案件事实问题。另外一种将统计证据的模型应用于其他理论当中，成为其他理论的重要研究手段，以达成为诉讼服务的目的。流行病学因果关系, 是流行病上所采用的因果关系的认识方法,。某因子与疾病之间的关系, 即使不能够从医学、药理学等观点进行详细的法则性证明, 但根据统计学的大量观察, 认为其间具有高度的盖然性时, 就可以肯定存在因果关系。流行病学因果关系理论不是依靠科学经验法则直接证明因果关系，而是立足于统计的事实，根据流行病上因果关系的判断理论，来推定行为与结果的因果关系。风险升高是流行病学因果关系中的重要概念，其指标包括归因风险，相对危险度，归因比率和全体归因比率。传统侵权行为法以因果关系作为要件，进而产生全有全无的赔偿效果，被学者诟病，认为全有全无原则无法达成法律的目的，并且无法在举证困难的案件中促进公平。提倡机会丧失的学者以此为基础，认为机会本身即具有价值，应予保护，并认为机会丧失理论较全有全无原则更能达成法律的目的，且有助于促进公平。环境诉讼中，环境污染的危害行为具有缓慢性，且长期下去后果严重。及时消除环境侵害源头避免损失后果扩大对于侵害人和受害人均意义重大。所以，在环境侵害中，以风险为基础，以机会丧失理论为方法解决诉讼中的证明难题，即可行，又有重大现实意义。为了解决环境诉讼中多因性因果关系认定的困局，最好的解决方案是放弃决定论因果关系理论中对与因果关系全有全无的坚持，转而承认过去事件的不决定性，并接受非决定论因果关系的概念，透过概率性因果概念建立起多因性因果证明困境的比例责任。

Environmental litigation as a new type of litigation has profound social background. The changing relationship of human and nature is the performance of the consciousness of the human environment, the clarity of the concept of environmental rights, environmental infringement of social reality and legal progress and development is an important reason for the rise of environmental litigation. Environmental litigation has its own characteristics, mainly for the public of the environmental litigation, the complexity of interests, professional, and difficulties in prive. This is not only , reflected on tortious and damages, the proof of causation in environmental litigation involves legislative, judicial, policy, science, technology, and many other factors, it is more complex than an ordinary action. The theories of causality is deep affected by philosophy, it is also a hot topic in law. The common law system and Civil law system had developed a variety of theories of causality, in order to guide practice. The gradual development of quantum mechanics breakthroughs the theory of classical mechanics. Determinism causation is replaced by non-deterministic causation. Using theory of probability and statistics to solve legal causality is the inherent requirements of modern litigation practice. The theory of relative causality provides theoretical basis for use probability and statisticsThe statistical evidence is the exemplification of probability statistics in legal proof. Statistical evidence is an evidence that using scientific statistical probability theory to proof in litigation. The concept of statistical evidence lies in the legal possibilities, requiring an observed random variable model and includes effective, clear and objective measure of the strength of evidence and to provide clear and objective means to control misleading and weaken the probability of the evidence. Statistical evidence can be uses in two forms in the litigation; one is using statistical probability results directly to prove the facts of the case. Another model of the statistical evidence is that the research methods of statistics can be used in other theories which are aiming to prove causation in environmental litigation.Epidemiological causation is the understanding of the epidemic on the causation. If we can not understand the relationship between a factor and disease from the science of medicine, pharmacology and other medical rules，according to the observations from statistics with a high degree of probability, there is certainly causality between them. Epidemiological causation theory, instead of relying on the scientific rule to prove causation directly, it is based on the statistical fact and judged by the causality on epidemic. In doing so, court can infer the causation between torts and damages. Heighten of risk is an important concept in epidemiological causation which including attributable risk, relative risk, attributable proportion and attributable proportion in the population.Causation is an essential elements in traditional tort law, result in making compensation into all-or-nothing status. The all-or-nothing principle cannot fulfill the aim of fair and justice of law. Scholars who are proponents of loss of chance hold that opportunity is valuable and should be protected. They also argue that loss of chance rule is better than all-or-nothing in tort law. For environmental litigation, the environmental pollution hazard behavior slowly, and go on the consequences may be discovered in a long-time. So eliminating the source of environmental pollution in timely is of great significance to the victims, therefore, it is practicable to use lost of chance theory in the proof of causation of environmental litigation. In order to solve the dilemma of environmental litigation in the causality, the best solution is to abandon the theory of determinism causality and accept the concept of non-determinism causality to establish the causation in environmental litigation.