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3.8.1.: Definitions and general considerations

3.8.1.1. Specific target organ toxicity (single exposure) is defined as specific, non lethal target organ toxicity arising from a single exposure to a substance or mixture. All significant health effects that can impair function, both reversible and irreversible, immediate and/or delayed and not specifically addressed in sections 3.1 to 3.7 and 3.10 are included (see also 3.8.1.6).
3.8.1.2. Classification identifies the substance or mixture as being a specific target organ toxicant and, as such, it may present a potential for adverse health effects in people who are exposed to it.
3.8.1.3. These adverse health effects produced by a single exposure include consistent and identifiable toxic effects in humans, or, in experimental animals, toxicologically significant changes which have affected the function or morphology of a tissue/organ, or have produced serious changes to the biochemistry or haematology of the organism, and these changes are relevant for human health.
3.8.1.4. Assessment shall take into consideration not only significant changes in a single organ or biological system but also generalised changes of a less severe nature involving several organs.
3.8.1.5. Specific target organ toxicity can occur by any route that is relevant for humans, i.e. principally oral, dermal or inhalation.
3.8.1.6. Specific target organ toxicity following a repeated exposure is classified as described in Specific target organ toxicity — Repeated exposure (section 3.9) and is therefore excluded from section 3.8. Other specific toxic effects, listed below, are assessed separately and consequently are not included here:
(a) Acute toxicity (section 3.1);
(b) Skin corrosion/irritation (section 3.2);
(c) Serious eye damage/eye irritation (section 3.3);
(d) Respiratory or skin sensitisation (section 3.4);
(e) Germ cell mutagenicity (section 3.5);
(f) Carcinogenicity (section 3.6);
(g) Reproductive toxicity (section 3.7); and
(h) Aspiration toxicity (section 3.10).
3.8.1.7. The hazard class Specific Target Organ Toxicity — Single Exposure is differentiated into:
Specific target organ toxicity — single exposure, Category 1 and 2;
Specific target organ toxicity — single exposure, Category 3.

See Table 3.8.1.


Table 3.8.1

Categories for specific target organ toxicity-single exposure

Categories

Criteria

Category 1

Substances that have produced significant toxicity in humans or that, on the basis of evidence from studies in experimental animals, can be presumed to have the potential to produce significant toxicity in humans following single exposure

Substances are classified in Category 1 for specific target organ toxicity (single exposure) on the basis of:

(a)  reliable and good quality evidence from human cases or epidemiological studies; or

(b)  observations from appropriate studies in experimental animals in which significant and/or severe toxic effects of relevance to human health were produced at generally low exposure concentrations. Guidance dose/concentration values are provided below (see 3.8.2.1.9) to be used as part of weight-of-evidence evaluation.

Category 2

Substances that, on the basis of evidence from studies in experimental animals can be presumed to have the potential to be harmful to human health following single exposure

Substances are classified in Category 2 for specific target organ toxicity (single exposure) on the basis of observations from appropriate studies in experimental animals in which significant toxic effects, of relevance to human health, were produced at generally moderate exposure concentrations. Guidance dose/concentration values are provided below (see 3.8.2.1.9) in order to help in classification.

In exceptional cases, human evidence can also be used to place a substance in Category 2 (see 3.8.2.1.6).

Category 3

Transient target organ effects

This category only includes narcotic effects and respiratory tract irritation. These are target organ effects for which a substance does not meet the criteria to be classified in Categories 1 or 2 indicated above. These are effects which adversely alter human function for a short duration after exposure and from which humans may recover in a reasonable period without leaving significant alteration of structure or function. Substances are classified specifically for these effects as laid down in 3.8.2.2.

Note: Attempts shall be made to determine the primary target organ of toxicity and to classify for that purpose, such as hepatotoxicants, neurotoxicants. The data shall be carefully evaluated and, where possible, secondary effects should not be included (e.g. a hepatotoxicant can produce secondary effects in the nervous or gastro-intestinal systems).