The Notification of New Substances Regulations 1993

PART II criteria for the categories of danger “very toxic”, “toxic” and “harmful”

Substances shall be classified as “very toxic”, “toxic” or “harmful” in accordance with the following criteria:

(a) Where the acute toxicity in animals of the commercial substance has been determined by a method which permits estimation of the LD50 or LC50, classification as very toxic, toxic or harmful shall be effected using the following parameters as reference values:

Category of danger	LD50 Oral in rat mg/kg body weight	LD50 Dermal in rat or rabbit mg/kg body weight	LC50 Inhalation in rat mg/litre/4 hrs
			gases and vapours	aerosols and particulates
Very toxic	≤25	≤50	≤0.5	≤0.25
Toxic	>25 to 200	>50 to 400	>0.5 to 2	>0.25 to 1
Harmful	>200 to 2000	>400 to 2000	>2 to 10	>1 to 5

(b) Where the acute oral toxicity in animals of the commercial substance has been determined using the fixed dose procedure, classification as very toxic, toxic or harmful shall be effected on the basis of the discriminating dose.This is the dose level which produces evident toxicity, but no mortality, and is one of four fixed dose levels (5, 50, 500 or 2000 mg/kg bodyweight). “Evident toxicity” is a term used to describe signs of toxicity following administration of a test substance, which are of a severity such that administration of the next higher fixed dose level would be expected to result in mortality.As this test method is based on the selection of doses from a series of fixed doses, it is inappropriate to give values for classification. The following parameters are used as reference values:

Category	Discriminating dose (mg/kg bodyweight)
The 2000 mg/kg dose level is used primarily to obtain information on signs of toxicity that may occur with substances which are of low acute toxicity and are not classified on the basis of acute toxicity;
Very toxic	<5
Toxic	5 to <50
Harmful	50 to <500

(c) If facts show that for the purposes of classification it is inadvisable to use the reference values given in paragraphs (a) and (b) because the substances produce other effects, the substances shall be classified according to the magnitude of these effects.