Appendix L-2

Discordant Substances for GHS Toxicity Category Predictions Using the
3T3 and NHK NRU Test Methods and Associated Regressions

*\[This Page Intentionally Left Blank\]*

**L.2 Discordant Substances for GHS Toxicity Category Predictions Using
the 3T3 and NHK NRU Test Methods and Associated Regressions**

This appendix provides a more detailed discussion of the discordant
substances identified for the GHS acute oral toxicity category
predictions using the NRU test methods and the regressions evaluated in
**Section 6.3.**

L.2.1 [Discordant Substances for Prediction of Toxicity Category by the
3T3 and NHK NRU Test Methods and the RC Millimole
Regression]{.underline}

**Table L2-1** identifies the discordant substances for which the *in
vitro* predicted GHS toxicity category (using the 3T3 and NHK NRU test
methods with the RC millimole regression) did not match the GHS toxicity
category assigned based on the reference rodent LD~50~ data. For the 3T3
NRU test method, the toxicity category was underpredicted for 20 (56%)
and overpredicted for 14 (43%) of the 34 discordant substances. Of the
14 substances for which toxicity was underpredicted,

-   8 (57%) were underpredicted by one toxicity category

-   2 (14%) were underpredicted by two toxicity categories

-   4 (29%) were underpredicted by three toxicity categories.

For the 20 substances for which toxicity was overpredicted,

-   14 (70%) were overpredicted by one toxicity category

-   6 (30%) were overpredicted by two toxicity categories.

For the NHK NRU test method, toxicity was underpredicted for 12 (54%)
and overpredicted for 22 (46%) of the 34 discordant substances. Of the
12 substances for which toxicity was underpredicted,

-   6 (50%) were underpredicted by one toxicity category

-   3 (25%) were underpredicted by two toxicity categories

-   2 (17%) were underpredicted by three toxicity categories

-   1 (8%) was underpredicted by four toxicity categories

For the 22 substances for which toxicity was overpredicted,

-   16 (73%) were overpredicted by one toxicity category

-   6 (27%) were overpredicted by two toxicity categories

The fact that there were more substances for which toxicity was
overpredicted is a result of the removal of substances with specific
mechanisms of toxicity that were not expected to be active in the 3T3
and NHK cell cultures. The toxicity for most of these substances would
have been underpredicted. **Figure 3-1** shows that most of the 58
selected RC chemicals are below the RC regression line. Thus, the RC
would predict lower toxicity (i.e., a higher LD~50~) for most of these
chemicals.

**Table L2-1 Discordant Substances^1^ for the Prediction of GHS^2^**
Toxicity Categories by the 3T3 and NHK NRU Test Methods and the RC
Millimole Regression

+----------+-------------+----------------+------------+---------------+
| **Rodent | **3T3 NRU   |                | **NHK NRU  |               |
| GHS**    | Test        |                | Test       |               |
|          | Method**    |                | Method**   |               |
| **       |             |                |            |               |
| Toxicity |             |                |            |               |
| Categ    |             |                |            |               |
| ory^3^** |             |                |            |               |
|          |             |                |            |               |
| **(      |             |                |            |               |
| mg/kg)** |             |                |            |               |
+==========+=============+================+============+===============+
|          | *           | **Toxicity**   | **         | **Toxicity**  |
|          | *Toxicity** |                | Toxicity** |               |
|          |             | **Un           |            | **Und         |
|          | **Over      | derpredicted** | **Overp    | erpredicted** |
|          | predicted** |                | redicted** |               |
+----------+-------------+----------------+------------+---------------+
| LD~50~   |             | Aminopterin    |            | Aminopterin   |
| \< 5     |             | (1)            |            | (4)           |
|          |             |                |            |               |
|          |             | Busulfan (3)   |            | Busulfan (3)  |
|          |             |                |            |               |
|          |             | Cycloheximide  |            | Cycloheximide |
|          |             | (1)            |            | (1)           |
|          |             |                |            |               |
|          |             | Mercury        |            | Mercury       |
|          |             | chloride (2)   |            | chloride (2)  |
|          |             |                |            |               |
|          |             | Phenylthiourea |            | P             |
|          |             | (3)            |            | henylthiourea |
|          |             |                |            | (3)           |
|          |             | Sodium         |            |               |
|          |             | selenate (3)   |            | Sodium        |
|          |             |                |            | selenate (2)  |
|          |             | Triet          |            |               |
|          |             | hylenemelamine |            | Trieth        |
|          |             | (1)            |            | ylenemelamine |
|          |             |                |            | (2)           |
+----------+-------------+----------------+------------+---------------+
| 5 \<     |             | Arsenic        |            | Arsenic       |
| LD~50~ ≤ |             | trioxide (1)   |            | trioxide (1)  |
| 50       |             |                |            |               |
|          |             | Digoxin (3)    |            | Sodium        |
|          |             |                |            | dichromate    |
|          |             | Sodium         |            | dihydrate (1) |
|          |             | arsenite (1)   |            |               |
|          |             |                |            | Thallium      |
|          |             | Sodium         |            | sulfate (1)   |
|          |             | dichromate     |            |               |
|          |             | dihydrate (1)  |            |               |
|          |             |                |            |               |
|          |             | Thallium       |            |               |
|          |             | sulfate (2)    |            |               |
+----------+-------------+----------------+------------+---------------+
| 50 \<    |             | Cupric sulfate | Hexac      | Cupric        |
| LD~50~ ≤ |             | pentahydrate   | hlorophene | sulfate       |
| 300      |             | (1)            | (1)        | pentahydrate  |
|          |             |                |            | (1)           |
|          |             | Sodium oxalate |            |               |
|          |             | (1)            |            | Sodium        |
|          |             |                |            | oxalate (1)   |
+----------+-------------+----------------+------------+---------------+
| 300 \<   |             |                |            |               |
| LD~50~ ≤ |             |                |            |               |
| 2000     |             |                |            |               |
+----------+-------------+----------------+------------+---------------+
| 2000 \<  | Ac          |                | Ace        |               |
| LD~50~ ≤ | etaminophen |                | taminophen |               |
| 5000     | (1)         |                | (1)        |               |
|          |             |                |            |               |
|          | A           |                | Ac         |               |
|          | cetonitrile |                | etonitrile |               |
|          | (1)         |                | (1)        |               |
|          |             |                |            |               |
|          | Boric acid  |                | Boric acid |               |
|          | (1)         |                | (1)        |               |
|          |             |                |            |               |
|          | Chlo        |                | Chlor      |               |
|          | ramphenicol |                | amphenicol |               |
|          | (1)         |                | (1)        |               |
|          |             |                |            |               |
|          | Citric acid |                | Citric     |               |
|          | (1)         |                | acid (1)   |               |
|          |             |                |            |               |
|          | Dimeth      |                | Lactic     |               |
|          | ylformamide |                | acid (1)   |               |
|          | (1)         |                |            |               |
|          |             |                | Potassium  |               |
|          | Lactic acid |                | chloride   |               |
|          | (1)         |                | (1)        |               |
|          |             |                |            |               |
|          | Potassium   |                | Sodium     |               |
|          | chloride    |                | c          |               |
|          | (1)         |                | hloride(1) |               |
|          |             |                |            |               |
|          | Sodium      |                | Trich      |               |
|          | chloride    |                | loroacetic |               |
|          | (1)         |                | acid (1)   |               |
|          |             |                |            |               |
|          | Tric        |                | Xylene (1) |               |
|          | hloroacetic |                |            |               |
|          | acid (1)    |                |            |               |
|          |             |                |            |               |
|          | Xylene (1)  |                |            |               |
+----------+-------------+----------------+------------+---------------+
| LD~50~   | 5-Ami       |                | 5-Amin     |               |
| \> 5000  | nosalicylic |                | osalicylic |               |
|          | acid (2)    |                | acid (2)   |               |
|          |             |                |            |               |
|          | Dibutyl     |                | Dibutyl    |               |
|          | phthalate   |                | phthalate  |               |
|          | (2)         |                | (2)        |               |
|          |             |                |            |               |
|          | Diethyl     |                | Diethyl    |               |
|          | phthalate   |                | phthalate  |               |
|          | (2)         |                | (2)        |               |
|          |             |                |            |               |
|          | Ethanol (2) |                | Ethanol    |               |
|          |             |                | (1)        |               |
|          | Ethylene    |                |            |               |
|          | glycol (1)  |                | Ethylene   |               |
|          |             |                | glycol (1) |               |
|          | Glycerol    |                |            |               |
|          | (1)         |                | G          |               |
|          |             |                | ibberellic |               |
|          | 2-Propanol  |                | acid (1)   |               |
|          | (2)         |                |            |               |
|          |             |                | Glycerol   |               |
|          | Sodium      |                | (1)        |               |
|          | h           |                |            |               |
|          | ypochlorite |                | Methanol   |               |
|          | (2)         |                | (2         |               |
|          |             |                |            |               |
|          | 1,1,1-Tric  |                | 2-Propanol |               |
|          | hloroethane |                | (2)        |               |
|          | (1)         |                |            |               |
|          |             |                | Sodium     |               |
|          |             |                | hy         |               |
|          |             |                | pochlorite |               |
|          |             |                | (2)        |               |
|          |             |                |            |               |
|          |             |                | 1          |               |
|          |             |                | ,1,1-Trich |               |
|          |             |                | loroethane |               |
|          |             |                | (1)        |               |
+----------+-------------+----------------+------------+---------------+

^1^Substances for which the *in vitro* predicted GHS toxicity category
was different from the GHS toxicity category assigned to the substance
based on reference rodent LD~50~ data. Numbers in parentheses indicate
the number of categories different. Three substances were excluded
because no rat LD~50~ was identified: epinephrine bitartrate,
colchicine, and propylparaben. Carbon tetrachloride was excluded from
the 3T3 and NHK NRU analyses because no laboratory attained sufficient
toxicity for the calculation of an IC~50~. Methanol was excluded from
the 3T3 analysis because no laboratory attained sufficient toxicity for
the calculation of an IC~50~. The 21 substances in **Table 6-3** were
excluded based on their mechanisms of action.

^2^GHS-Globally Harmonized System of Classification and Labelling of
Chemicals with LD~50~ in mg/kg (UN 2005). The RC millimole regression is
log LD~50~ (mmol/kg) = log IC~50~ (mM) X 0.435 + 0.625.

^3^Reference rodent LD~50~ values in from **Table 3-2**.

L.2.2 [Discordant Substances for Prediction of Toxicity Category by the
3T3 and NHK NRU Test Methods and the RC Rat-Only Weight
Regression]{.underline}

**Table L2-2** shows the discordant substances for which the *in vitro*
predicted GHS toxicity category (using the 3T3 and NHK NRU test methods
with the RC rat-only weight regression) did not match that based on the
reference rodent LD~50~ data. The two *in vitro* NRU cytotoxicity test
methods over- and under-predicted the GHS toxicity category for a
similar number of substances. For the 3T3 NRU test method, the GHS
toxicity category of 19 (63%) of 30 discordant substances was
overpredicted, with:

-   13 (68%) overpredicted by one GHS toxicity category

-   6 (32%) overpredicted by two GHS toxicity categories

The toxicity of fewer substances (11; 37%) was underpredicted by this
test method, with:

-   7 (64%) underpredicted by one GHS toxicity category

-   4 (36%) underpredicted by two GHS toxicity categories

For the NHK NRU test method, the GHS toxicity category of 22 (67%) of
the 33 discordant substances was overpredicted. Of these,

-   15 (68%) were overpredicted by one GHS toxicity category

-   7 (31%) were overpredicted by two GHS toxicity categories

For this assay, the toxicity of 11 (33%) of the discordant substances
was underpredicted, with

-   6 (55%) underpredicted by one GHS toxicity category

-   4 (36%) underpredicted by two GHS toxicity categories

-   1 (9%) underpredicted by three toxicity categories.

Phenylthiourea, the substance for which the GHS toxicity category was
underpredicted by three toxicity categories, was in the most severe GHS
toxicity category (i.e., LD~50~ \< 5 mg/kg).

**Table L2-2 Discordant substances^1^ for RC Rat-Only Weight Regression
Prediction of GHS Toxicity Categories^2^** by the 3T3 and NHK NRU Test
Methods

+-----------+----------------+-------------+-------------+-------------+
| **Rodent  | **3T3 NRU Test |             | **NHK NRU   |             |
| GHS**     | Method**       |             | Test        |             |
|           |                |             | Method**    |             |
| *         |                |             |             |             |
| *Toxicity |                |             |             |             |
| Cate      |                |             |             |             |
| gory^3^** |                |             |             |             |
|           |                |             |             |             |
| **        |                |             |             |             |
| (mg/kg)** |                |             |             |             |
+===========+================+=============+=============+=============+
|           | **Toxicity**   | *           | *           | *           |
|           |                | *Toxicity** | *Toxicity** | *Toxicity** |
|           | **O            |             |             |             |
|           | verpredicted** | **Under     | **Over      | **Under     |
|           |                | predicted** | predicted** | predicted** |
+-----------+----------------+-------------+-------------+-------------+
| LD~50~ \< |                | Cy          |             | Cy          |
| 5         |                | cloheximide |             | cloheximide |
|           |                | (1)         |             | (1)         |
|           |                |             |             |             |
|           |                | Phe         |             | Phe         |
|           |                | nylthiourea |             | nylthiourea |
|           |                | (2)         |             | (3)         |
|           |                |             |             |             |
|           |                | Sodium      |             | Sodium      |
|           |                | selenate    |             | selenate    |
|           |                | (2)         |             | (2)         |
|           |                |             |             |             |
|           |                | Triethyl    |             | Triethyl    |
|           |                | enemelamine |             | enemelamine |
|           |                | (1)         |             | (2)         |
+-----------+----------------+-------------+-------------+-------------+
| 5 \<      |                | Arsenic     |             | Aminopterin |
| LD~50~ ≤  |                | trioxide    |             | (2)         |
| 50        |                | (1)         |             |             |
|           |                |             |             | Arsenic     |
|           |                | Busulfan    |             | trioxide    |
|           |                | (2)         |             | (1)         |
|           |                |             |             |             |
|           |                | Digoxin (2) |             | Busulfan    |
|           |                |             |             | (2)         |
|           |                | Mercury     |             |             |
|           |                | chloride    |             | Mercury     |
|           |                | (1)         |             | chloride    |
|           |                |             |             | (1)         |
|           |                | Thallium    |             |             |
|           |                | sulfate (1) |             | Sodium      |
|           |                |             |             | arsenite    |
|           |                | Sodium      |             | (1)         |
|           |                | arsenite    |             |             |
|           |                | (1)         |             | Thallium    |
|           |                |             |             | Sulfate (1) |
+-----------+----------------+-------------+-------------+-------------+
| 50 \<     |                | Sodium      | Hexa        | Sodium      |
| LD~50~ ≤  |                | fluoride    | chlorophene | fluoride    |
| 300       |                | (1)         | (1)         | (1)         |
+-----------+----------------+-------------+-------------+-------------+
| 300 \<    | Propranolol    |             | T           |             |
| LD~50~ ≤  | (1)            |             | riphenyltin |             |
| 2000      |                |             | hydroxide   |             |
|           | Triphenyltin   |             | (2)         |             |
|           | hydroxide (2)  |             |             |             |
+-----------+----------------+-------------+-------------+-------------+
| 2000 \<   | Acetaminophen  |             | 5-Ami       |             |
| LD~50~ ≤  | (1)            |             | nosalicylic |             |
| 5000      |                |             | acid (1)    |             |
|           | 5-             |             |             |             |
|           | Aminosalicylic |             | Chlo        |             |
|           | acid (1)       |             | ramphenicol |             |
|           |                |             | (1)         |             |
|           | Boric acid (1) |             |             |             |
|           |                |             | Boric acid  |             |
|           | C              |             | (1)         |             |
|           | hloramphenicol |             |             |             |
|           | (1)            |             | Xylene (1)  |             |
|           |                |             |             |             |
|           | Xylene (1)     |             | Ac          |             |
|           |                |             | etaminophen |             |
|           |                |             | (1)         |             |
|           |                |             |             |             |
|           |                |             | Lactic acid |             |
|           |                |             | (1)         |             |
|           |                |             |             |             |
|           |                |             | Sodium      |             |
|           |                |             | chloride    |             |
|           |                |             | (1)         |             |
|           |                |             |             |             |
|           |                |             | Potassium   |             |
|           |                |             | chloride    |             |
|           |                |             | (1)         |             |
+-----------+----------------+-------------+-------------+-------------+
| LD~50~ \> | Citric acid    |             | Citric acid |             |
| 5000      | (2)            |             | (2)         |             |
|           |                |             |             |             |
|           | Diethyl        |             | Dibutyl     |             |
|           | phthalate (2)  |             | phthalate   |             |
|           |                |             | (2)         |             |
|           | Dibutyl        |             |             |             |
|           | phthalate (2)  |             | Diethyl     |             |
|           |                |             | phthalate   |             |
|           | Dim            |             | (2)         |             |
|           | ethylformamide |             |             |             |
|           | (1)            |             | Dimeth      |             |
|           |                |             | ylformamide |             |
|           | Ethanol (1)    |             | (1)         |             |
|           |                |             |             |             |
|           | Ethylene       |             | Ethanol (1) |             |
|           | glycol (1)     |             |             |             |
|           |                |             | Gibberellic |             |
|           | Gibberellic    |             | Acid (1)    |             |
|           | acid (1)       |             |             |             |
|           |                |             | Glycerol    |             |
|           | Glycerol (1)   |             | (1)         |             |
|           |                |             |             |             |
|           | 2-Propanol (1) |             | Methanol    |             |
|           |                |             | (2)         |             |
|           | Sodium         |             |             |             |
|           | hypochlorite   |             | 2-Propanol  |             |
|           | (2)            |             | (1)         |             |
|           |                |             |             |             |
|           | T              |             | Sodium      |             |
|           | richloroacetic |             | h           |             |
|           | acid (2)       |             | ypochlorite |             |
|           |                |             | (2)         |             |
|           | 1,1,1-T        |             |             |             |
|           | richloroethane |             | Tric        |             |
|           | (1)            |             | hloroacetic |             |
|           |                |             | acid (2)    |             |
|           |                |             |             |             |
|           |                |             | 1,1,1-Tric  |             |
|           |                |             | hloroethane |             |
|           |                |             | (1)         |             |
+-----------+----------------+-------------+-------------+-------------+

^1^Substances for which the *in vitro* predicted GHS toxicity category
was different from that based on the reference rodent LD~50~ data.
Numbers in parentheses indicate the number of categories different.
Three substances were excluded because no rat LD~50~ was identified:
epinephrine bitartrate, colchicine, and propylparaben. Carbon
tetrachloride was excluded from the 3T3 and NHK NRU analyses because no
laboratory attained sufficient toxicity for the calculation of an
IC~50~. Methanol was excluded from the 3T3 NRU analysis because no
laboratory attained sufficient toxicity for the calculation of an
IC~50~. The 21 substances in **Table 6-3** were excluded based on their
mechanisms of action.

^2^GHS-Globally Harmonized System of Classification and Labelling of
Chemicals with LD~50~ in mg/kg (UN 2005). The RC rat-only weight
regression is log LD~50~ (mg/kg) = log IC~50~ (μg/mL) X 0.372 + 2.024.

^3^Reference rodent LD~50~ values from **Table 4-2**.

L.2.3 [Discordant Substances for the Prediction of Toxicity Category by
the 3T3 and NHK NRU Test Methods and the RC Rat-Only Weight Regression
Excluding Substances with Specific Mechanisms of Toxicity]{.underline}

**Table L2-3** shows the discordant substances for which the *in vitro*
NRU predicted toxicity category (using the 3T3 and NHK NRU test methods
with the RC rat-only weight regression excluding substances with
specific mechanisms of toxicity) did not match that based on the
reference rodent LD~50~ data. The NHK NRU test method had four more
discordant substances than the corresponding assay using 3T3 cells when
the IC~50~ results were applied to the RC rat-only weight regression,
after excluding substances with specific mechanisms of toxicity. For the
3T3 NRU test method, the GHS toxicity category of 19 (63%) of 30
discordant substances was overpredicted, with

-   13 (68%) overpredicted by one toxicity category

-   6 (32%) overpredicted by two toxicity categories

The toxicity of 11 (37%) of 30 discordant substances was underpredicted
by the 3T3 NRU test method, with

-   7 (64%) underpredicted by one category

-   4 (36%) underpredicted by two toxicity categories

For the NHK NRU test method, the toxicity of 22 (65%) of 34 discordant
substances was overpredicted, with

-   15 (68%) overpredicted by one category

-   7 (32%) overpredicted by two toxicity categories

Also, for this test method, the toxicity of 12 (35%) of 34 discordant
substances was underpredicted, with

-   6 (50%) underpredicted by one toxicity category

-   4 (33%) underpredicted by two toxicity categories

-   2 (17%) underpredicted by three toxicity categories

Both substances for which toxicity was underpredicted by three toxicity
categories were in the most severe GHS toxicity category (i.e., LD~50~
\< 5 mg/kg).

**Table L2-3 Discordant Substances^1^ for RC Rat-Only Weight Regression
Excluding Chemicals with Specific Mechanisms of Toxicity Prediction of
GHS Toxicity Categories^2^** by the 3T3 and NHK NRU Test Methods

+------------+-------------+-------------+--------------+--------------+
| **Rodent   | **3T3 NRU   |             | **NHK NRU    |              |
| GHS**      | Test        |             | Test         |              |
|            | Method**    |             | Method**     |              |
| **         |             |             |              |              |
| Toxicity** |             |             |              |              |
|            |             |             |              |              |
| **Cat      |             |             |              |              |
| egory^3^** |             |             |              |              |
|            |             |             |              |              |
| *          |             |             |              |              |
| *(mg/kg)** |             |             |              |              |
+============+=============+=============+==============+==============+
|            | *           | *           | **Toxicity** | **Toxicity** |
|            | *Toxicity** | *Toxicity** |              |              |
|            |             |             | **Ove        | **Unde       |
|            | **Over      | **Under     | rpredicted** | rpredicted** |
|            | predicted** | predicted** |              |              |
+------------+-------------+-------------+--------------+--------------+
| LD~50~ \<  |             | Cy          |              | C            |
| 5          |             | cloheximide |              | ycloheximide |
|            |             | (1)         |              | (1)          |
|            |             |             |              |              |
|            |             | Phe         |              | Disulfoton   |
|            |             | nylthiourea |              | (3)          |
|            |             | (2)         |              |              |
|            |             |             |              | Ph           |
|            |             | Sodium      |              | enylthiourea |
|            |             | selenate    |              | (3)          |
|            |             | (2)         |              |              |
|            |             |             |              | Sodium       |
|            |             | Triethyl    |              | selenate (2) |
|            |             | enemelamine |              |              |
|            |             | (1)         |              | Triethy      |
|            |             |             |              | lenemelamine |
|            |             |             |              | (2)          |
+------------+-------------+-------------+--------------+--------------+
| 5 \<       |             | Arsenic     |              | Aminopterin  |
| LD~50~ ≤   |             | trioxide    |              | (2)          |
| 50         |             | (1)         |              |              |
|            |             |             |              | Arsenic      |
|            |             | Busulfan    |              | trioxide (1) |
|            |             | (2)         |              |              |
|            |             |             |              | Busulfan (2) |
|            |             | Digoxin (2) |              |              |
|            |             |             |              | Mercury      |
|            |             | Mercury     |              | chloride (1) |
|            |             | chloride    |              |              |
|            |             | (1)         |              | Sodium       |
|            |             |             |              | arsenite (1) |
|            |             | Thallium    |              |              |
|            |             | sulfate (1) |              | Thallium     |
|            |             |             |              | sulfate (1)  |
|            |             | Sodium      |              |              |
|            |             | arsenite    |              |              |
|            |             | (1)         |              |              |
+------------+-------------+-------------+--------------+--------------+
| 50 \<      |             | Sodium      | Hex          | Sodium       |
| LD~50~ ≤   |             | fluoride    | achlorophene | fluoride (1) |
| 300        |             | (1)         | (1)          |              |
+------------+-------------+-------------+--------------+--------------+
| 300 \<     | Propranolol |             | Triphenyltin |              |
| LD~50~ ≤   | (1)         |             | hydroxide    |              |
| 2000       |             |             | (2)          |              |
|            | T           |             |              |              |
|            | riphenyltin |             |              |              |
|            | hydroxide   |             |              |              |
|            | (2)         |             |              |              |
+------------+-------------+-------------+--------------+--------------+
| 2000 \<    | Ac          |             | 5-Am         |              |
| LD~50~ ≤   | etaminophen |             | inosalicylic |              |
| 5000       | (1)         |             | acid (1)     |              |
|            |             |             |              |              |
|            | 5-Ami       |             | Chl          |              |
|            | nosalicylic |             | oramphenicol |              |
|            | acid (1)    |             | (1)          |              |
|            |             |             |              |              |
|            | Boric acid  |             | Boric acid   |              |
|            | (1)         |             | (1)          |              |
|            |             |             |              |              |
|            | Chlo        |             | Xylene (1)   |              |
|            | ramphenicol |             |              |              |
|            | (1)         |             | A            |              |
|            |             |             | cetaminophen |              |
|            | Xylene (1)  |             | (1)          |              |
|            |             |             |              |              |
|            |             |             | Lactic acid  |              |
|            |             |             | (1)          |              |
|            |             |             |              |              |
|            |             |             | Sodium       |              |
|            |             |             | chloride (1) |              |
|            |             |             |              |              |
|            |             |             | Potassium    |              |
|            |             |             | chloride (1) |              |
+------------+-------------+-------------+--------------+--------------+
| LD~50~ \>  | Citric acid |             | Citric acid  |              |
| 5000       | (2)         |             | (2)          |              |
|            |             |             |              |              |
|            | Diethyl     |             | Dibutyl      |              |
|            | phthalate   |             | phthalate    |              |
|            | (2)         |             | (2)          |              |
|            |             |             |              |              |
|            | Dibutyl     |             | Diethyl      |              |
|            | phthalate   |             | phthalate    |              |
|            | (2)         |             | (2)          |              |
|            |             |             |              |              |
|            | Dimeth      |             | Dimet        |              |
|            | ylformamide |             | hylformamide |              |
|            | (1)         |             | (1)          |              |
|            |             |             |              |              |
|            | Ethanol (1) |             | Ethanol (1)  |              |
|            |             |             |              |              |
|            | Ethylene    |             | Gibberellic  |              |
|            | glycol (1)  |             | acid (1)     |              |
|            |             |             |              |              |
|            | Gibberellic |             | Glycerol (1) |              |
|            | acid (1)    |             |              |              |
|            |             |             | Methanol (2) |              |
|            | Glycerol    |             |              |              |
|            | (1)         |             | 2-Propanol   |              |
|            |             |             | (1)          |              |
|            | 2-Propanol  |             |              |              |
|            | (1)         |             | Sodium       |              |
|            |             |             | hypochlorite |              |
|            | Sodium      |             | (2)          |              |
|            | h           |             |              |              |
|            | ypochlorite |             | Tri          |              |
|            | (2)         |             | chloroacetic |              |
|            |             |             | acid (2)     |              |
|            | Tric        |             |              |              |
|            | hloroacetic |             | 1,1,1-Tri    |              |
|            | acid (2)    |             | chloroethane |              |
|            |             |             | (1)          |              |
|            | 1,1,1-Tric  |             |              |              |
|            | hloroethane |             |              |              |
|            | (1)         |             |              |              |
+------------+-------------+-------------+--------------+--------------+

^1^Substances for which the *in vitro* predicted GHS toxicity category
was different from that based on the reference rodent LD~50~ data.
Numbers in parentheses indicate the number of categories different.
Three substances were excluded because no rat LD~50~ was identified:
epinephrine bitartrate, colchicine, and propylparaben. Carbon
tetrachloride was excluded from the 3T3 and NHK NRU analyses because no
laboratory attained sufficient toxicity for the calculation of an
IC~50~. Methanol was excluded from the 3T3 NRU analysis because no
laboratory attained sufficient toxicity for the calculation of an
IC~50~. The 21 substances in **Table 6-3** were excluded based on their
mechanisms of action.

^2^GHS-Globally Harmonized System of Classification and Labelling of
Chemicals with LD~50~ in mg/kg (UN 2005). The RC rat minus specific
mechanisms regression is log LD~50~ (mg/kg) = log IC~50~ (μg/mL) X
0.357 + 2.194.

^3^Reference rodent LD~50~ values from **Table 4-2**.

*\[This Page Intentionally Left Blank\]*