Methods of hazard identification

The type of toxic effect and the dose level at which it occurs are important issues in hazard identification (see Figure 17.2).

The test requirements are not necessarily the same for all food components. They will be influenced by properties of the substance such as:

- expected toxicity

- human exposure levels and pattern of use

- natural occurrence of the component in foods

- occurrence as a normal body constituent

- use in traditional foods

- knowledge of effects in man

It is impossible to give a detailed review of all the requirements for the safety assessment of a new food component here. Only a general outline of the approach will be presented.

The first step is to track the existing literature to find out whether the new chemical, or one which is structurally related, has been tested in the past. Once such information is collected, it is possible to design a program for safety testing to cover the pattern in which use toxic use toxic

Figure 17.2 Dose-response curve. The steepness and shape of the dose-response curve indicate the size of the hazard as the dose or exposure is increased. Substances showing a steep curve with a low threshold before any toxic effect is detected, are of the greatest concern because their safety margin is very narrow.

Figure 17.2 Dose-response curve. The steepness and shape of the dose-response curve indicate the size of the hazard as the dose or exposure is increased. Substances showing a steep curve with a low threshold before any toxic effect is detected, are of the greatest concern because their safety margin is very narrow.

the new food component is used. This would typically include studies of some or all of the following aspects:

- potential to cause mutagenesis in bacteria and mammalian cells

- absorption, distribution, metabolism, and excretion

- toxicity on repeated exposure for 4, 13, or 52 weeks in rodents

- effects on the reproductive systems and fetal development

- carcinogenic potential (e.g., 2-year feeding study in rodents)

- effect on the immune system

- effect on the nervous system

- effect on the endocrine system

- special studies on underlying mechanisms

The purpose of such tests is to build up a toxicological profile of the test material and to understand the dose-response relationship for any toxic response. A key determination is the assessment of the no-effect level from the feeding studies. Determination of the no-effect level depends primarily on the proper selection of doses for the study. Ideally, the highest dose should exert a toxic effect, whereas the lowest dose (a multiple of the human exposure level) should not show the effect. Additional dose groups are spaced between the top and bottom dose to define the dose-response curve further.

The risk assessment is carried out by determining the no-observed-adverse-affect-level (NOAEL) which is the highest dose in the most sensitive animal species which causes no toxic effects. The NOAEL is then divided by a safety factor to set an acceptable daily intake (ADI) level. The ADI is an estimate of the amount of a food additive, expressed on a body weight basis, that can be ingested daily over a lifetime without appreciable health risk. Substances that accumulate in the body are not suitable for use as additive. ADIs are only allocated to those additives that are substantially cleared from the body within 24 hours.

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