A regulation is of individual concern to a person where, in the light of the specific circumstances of the case concerned, it adversely affects a particular right on which that person could rely.

Furthermore, by terminating or, at the least, suspending the procedure which had been opened, at the request of an economic operator, for the purposes of obtaining a new authorisation of virginiamycin as an additive in feedingstuffs, and in the course of which that operator had the benefit of procedural guarantees, Regulation No 2821/98 providing for the withdrawal of the authorisation to market certain additives in feedingstuffs, including virginiamycin, within the Community affects that operator by reason of a legal and factual situation which differentiates it from all other persons. That fact is also such as to distinguish it for the purposes of the fourth paragraph of Article 173 of the Treaty (now, after amendment, the fourth paragraph of Article 230 EC).

In accordance with Article 130r(2) of the Treaty (now, after amendment, Article 174(2) EC), the precautionary principle is one of the principles on which Community policy on the environment is based. The principle also applies where the Community institutions take, in the framework of the common agricultural policy, measures to protect human health. It is apparent from Article 130r(1) and (2) of the Treaty that Community policy on the environment is to pursue the objective inter alia of protecting human health, that the policy, which aims at a high level of protection, is based in particular on the precautionary principle and that the requirements of the policy must be integrated into the definition and implementation of other Community policies. Furthermore, as the third subparagraph of Article 129(1) of the Treaty (now, after amendment, Article 152 EC) provides, and in accordance with settled case-law, health protection requirements form a constituent part of the Community's other policies and must therefore be taken into account when the common agricultural policy is implemented by the Community institutions.

The Community institutions may lay down for themselves guidelines for the exercise of their discretionary powers by way of measures not provided for in Article 189 of the Treaty (now Article 249 EC), in particular by communications, provided that they contain directions on the approach to be followed by the Community institutions and do not depart from the Treaty rules. In such circumstances, the Community judicature ascertains, applying the principle of equal treatment, whether the disputed measure is consistent with the guidelines that the institutions have laid down for themselves by adopting and publishing such communications.

Where there is scientific uncertainty as to the existence or extent of risks to human health, the Community institutions may, by reason of the precautionary principle, take protective measures without having to wait until the reality and seriousness of those risks become fully apparent.

It follows, first, that as a result of the precautionary principle, as enshrined in Article 130r(2) of the Treaty (now, after amendment, Article 174(2) EC), the Community institutions were entitled to take a preventive measure regarding the use of virginiamycin as an additive in feedingstuffs, even though, owing to existing scientific uncertainty, the reality and the seriousness of the risks to human health associated with that use were not yet fully apparent. A fortiori, the Community institutions were not required, for the purpose of taking preventive action, to wait for the adverse effects of the use of the product as a growth promoter to materialise. Thus, in a situation in which the precautionary principle is applied, which by definition coincides with a situation in which there is scientific uncertainty, a risk assessment cannot be required to provide the Community institutions with conclusive scientific evidence of the reality of the risk and the seriousness of the potential adverse effects were that risk to become a reality.

However, a preventive measure cannot properly be based on a purely hypothetical approach to the risk, founded on mere conjecture which has not been scientifically verified. It follows from the Community Courts' interpretation of the precautionary principle that a preventive measure may be taken only if the risk, although the reality and extent thereof have not been fully demonstrated by conclusive scientific evidence, appears nevertheless to be adequately backed up by the scientific data available at the time when the measure was taken.

The taking of measures, even preventive ones, on the basis of a purely hypothetical risk is particularly inappropriate in the matter of additives in feedingstuffs. In such matters a zero risk does not exist, since it is not possible to prove scientifically that there is no current or future risk associated with the addition of antibiotics to feedingstuffs. Moreover, that approach is even less appropriate in a situation in which the legislation already makes provision, as one of the possible ways of giving effect to the precautionary principle, for a procedure for prior authorisation of the products concerned.

The precautionary principle can therefore apply only in situations in which there is a risk, notably to human health, which, although it is not founded on mere hypotheses that have not been scientifically confirmed, has not yet been fully demonstrated.

In such a situation, risk thus constitutes a function of the probability that use of a product or a procedure will adversely affect the interests safeguarded by the legal order.

Consequently, the purpose of a risk assessment is to assess the degree of probability of a certain product or procedure having adverse effects on human health and the seriousness of any such adverse effects.

In the assessment of risk, it is for the Community institutions to determine the level of risk - i.e. the critical probability threshold for adverse effects on human health and for the seriousness of those possible effects - which in their judgment is no longer acceptable for society and above which it is necessary, in the interests of protecting human health, to take preventive measures in spite of any existing scientific uncertainty.

Although they may not take a purely hypothetical approach to risk and may not base their decisions on a zero-risk, the Community institutions must nevertheless take account of their obligation under the first subparagraph of Article 129(1) of the Treaty (now, after amendment, Article 152 EC) to ensure a high level of human health protection, which, to be compatible with that provision, does not necessarily have to be the highest that is technically possible.

The level of risk deemed unacceptable will depend on the assessment made by the competent public authority of the particular circumstances of each individual case. In that regard, the authority may take account, inter alia, of the severity of the impact on human health were the risk to occur, including the extent of possible adverse effects, the persistency or reversibility of those effects and the possibility of delayed effects as well as of the more or less concrete perception of the risk based on available scientific knowledge.

In matters relating to additives in feedingstuffs the Community institutions are responsible for carrying out complex technical and scientific assessments. In such circumstances a scientific risk assessment must be carried out before any preventive measures are taken.

A scientific risk assessment is commonly defined, at both international level and Community level, as a scientific process consisting in the identification and characterisation of a hazard, the assessment of exposure to the hazard and the characterisation of the risk.

The competent public authority must, in compliance with the relevant provisions, entrust a scientific risk assessment to experts who, once the scientific process is completed, will provide it with scientific advice.

Scientific advice is of the utmost importance at all stages of the drawing up and implementation of new legislation and for the execution and management of existing legislation. The duty imposed on the Community institutions by the first subparagraph of Article 129(1) of the Treaty to ensure a high level of human health protection means that they must ensure that their decisions are taken in the light of the best scientific information available and that they are based on the most recent results of international research.

Thus, in order to fulfil its function, scientific advice on matters relating to consumer health must, in the interests of consumers and industry, be based on the principles of excellence, independence and transparency.

When the precautionary principle is applied, it may prove impossible to carry out a full risk assessment because of the inadequate nature of the available scientific data. A full risk assessment may require long and detailed scientific research. Unless the precautionary principle is to be rendered nugatory, the fact that it is impossible to carry out a full scientific risk assessment does not prevent the competent public authority from taking preventive measures, at very short notice if necessary, when such measures appear essential given the level of risk to human health which the authority has deemed unacceptable for society.

The competent public authority must therefore weigh up its obligations and decide either to wait until the results of more detailed scientific research become available or to act on the basis of the scientific information available. Where measures for the protection of human health are concerned, the outcome of that balancing exercise will depend, account being taken of the particular circumstances of each individual case, on the level of risk which the authority deems unacceptable for society.

Where experts carry out a scientific risk assessment, the competent public authority must be given sufficiently reliable and cogent information to allow it to understand the ramifications of the scientific question raised and decide upon a policy in full knowledge of the facts. Consequently, if it is not to adopt arbitrary measures, which cannot in any circumstances be rendered legitimate by the precautionary principle, the competent public authority must ensure that any measures that it takes, even preventive measures, are based on as thorough a scientific risk assessment as possible, account being taken of the particular circumstances of the case at issue. Notwithstanding the existing scientific uncertainty, the scientific risk assessment must enable the competent public authority to ascertain, on the basis of the best available scientific data and the most recent results of international research, whether matters have gone beyond the level of risk that it deems acceptable for society. That is the basis on which the authority must decide whether preventive measures are called for and, should that be the case, which measures appear to it to be appropriate and necessary to prevent the risk from materialising.

In matters concerning the common agricultural policy the Community institutions enjoy a broad discretion regarding definition of the objectives to be pursued and choice of the appropriate means of action. In that regard, review by the Community judicature of the substance of the relevant act must be confined to examining whether the exercise of such discretion is vitiated by a manifest error or a misuse of powers or whether the Community institutions clearly exceeded the bounds of their discretion.

The Community institutions enjoy a broad discretion, in particular when determining the level of risk deemed unacceptable for society.

Where a Community authority is required to make complex assessments in the performance of its duties, its discretion also applies, to some extent, to the establishment of the factual basis of its action.

It follows that judicial review of the Community institutions' performance of their duty must be limited. The Community judicature is not entitled to substitute its assessment of the facts for that of the Community institutions, on which the Treaty confers sole responsibility for that duty. Instead, it must confine itself to ascertaining whether the exercise by the institutions of their discretion in that regard is vitiated by a manifest error or a misuse of powers or whether the institutions clearly exceeded the bounds of their discretion.