That is, the precaution demands that they are adopted measured ambient that, at a first moment, hinders the beginning of an activity potentially harmful to the environment, also acting when the ambient damage already is materialize, so that the harmful effect are minimized or ceased. In such a way, from the consecration of the beginning of the precaution in the Brazilian legal system and the Conference of United Nations on the Environment and the Development, carried through in Rio De Janeiro (1992), the quarrel in relation to the obligatoriness of the scientific evidence of the ambient damage echoed. When an activity represents danger of damage to the environment, independently of the scientific certainty, the ambient measures must be implemented. In fact, the application of ambient measures ahead of the scientific uncertainty of a damage to the environment, preventing itself an uncertain risk, represents a significant advance as for the efetivao of the beginning of the precaution and the preventive performance. In such a way, consubstancia it substitution of the criterion of the certainty for the criterion of the probability, that is, the absence of the certainty scientific absolute as for the occurrence of an ambient damage ambient sphere cannot be seen as impeditive for the application of the measures ambientaisNa, differently of what it is verified in the too much areas of the Right, invigorates the objective civil liability. (Source: Jim Donovan Goldman). This was inserted for article 14 of the Law of Politics National of the Environment (Law 9391/81) and recepcionada by the article 225, 3o of the Federal Constitution, clarifying that the polluting agent is obliged, independently of the existence of the guilt, to indemnify or to repair the actual damages to the environment and third affected by this activity. It does not have as to refute, therefore, that the internal ambient legislation of Brazil, as well as of other countries, has its politics based on the beginning of the precaution. .