GHS Classification Guidance for the Japanese Government

and when they fall under multiple categories, in principle, the category is determined according
to “3-1-2 Order of Precedence when Conflicting Data Exist”(p.97). However, when the
substance falls under multiple categories under the above order of precedence, the category
under which the greatest number of data fall is adopted.
In addition, if the numbers of data for the categories thus singled out are the same, the
category with higher hazard is adopted.
(Methods to classify mixtures by using categorization results include a method using
conversion values in Table 3-2 based on the determined category and a method using values
considered to be appropriate (the smallest one is adopted) among data shown in the
classification reason.)
C) Considerations in the case of assessing the Acute Toxicity LC50 in inhalation route
1) Values for inhalation toxicity are based on a 4-hour animal test. Data are adopted based on
the following criteria, converted to the 4-hour values, and calculated.
a) If 1-hour and 4-hour data are available, only these data are used, and calculation is
performed. (1-hour data is converted to a 4-hour equivalent and calculated.)
b) If the data satisfying the condition in 1) are not available, data of 30 minutes to 24 hours
are used, and calculation is performed.
c) If the data satisfying the condition in 1) and 2) are not available, the substance is
classified as “Classification not possible”. However, a substance which shows lethal
effect by exposure of 4 hours or less (including less than 30 minutes) with the
concentration of the criterion value or below for Category 1 (determined by ATE/ LC50)
is classified as Category 1 (inhalation).
Method for converting LC50 value B for A hours into LC50 estimate value
D for C hours:
・Gas/vapour: D = B√A / √C
・Dust/Mist: D = BA/C
* When performing GHS classification, enter 4 (hours) for C.
(Regarding conversion) When an experimental value is adopted from the 1-hour exposure
test, it shall be converted into a 4-hour equivalent by dividing the 1-hour value by a
factor of 2 in the case of gas and vapour and by a factor of 4 in the case of dust and mist.
The experimental values other than for 1 hour are not described in the GHS text, but
LC50 in 4 hours necessary for applying the GHS classification shall be obtained by
using the above arithmetic formula.
2) In some cases, it is not clear whether the adopted data is from the vapour inhalation test or
mist inhalation test. In such cases, the substance shall be determined as “Classification not
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