Last reviewed 31 March 2016

It is often said by some, that there is no correlation between classification, labelling and packaging (CLP) classes and categories, and Transport of Dangerous Goods (TDG) classes and packing groups. In this article our consultant editor, Desmond Waight tries to dispel this myth and clarify the situation.

Introduction

The introduction in the early noughties of the UN’s recommendations for a Globally Harmonised System of Classification and Labelling (GHS or Purple Book — from the colour chosen for the printed version’s cover) was supposed to harmonise the various systems in use for the supply of hazardous chemical, the TDG, the disposal of hazardous wastes, the control of major accident hazard sites, etc.

For the supply of hazardous chemicals in Europe, this meant a change from an old system, based on EU Directives requiring national laws, which in Great Britain (GB) were known as Chemicals (Hazard Information and Packaging for Supply) Regulations 2009 (SI 2009 No. 716) (CHIP) to a new EU directly acting regulation, the CLP (the full title being EC Regulation 1272/2008 on classification, labelling and packaging of substances and mixtures).

For transport, however, more modest rejigging was required — partly because for the physical hazards the GHS system simply adopted the existing TDG provisions, and partly because the safety hazards in transport are also those needing attention in the workplace. In the environmental hazards area, when transport decided to harmonise across the modes, it chose to base its requirements on the GHS recommendations.

CLP v TDG

So there is quite a correlation now between GHS (CLP) hazard classes and transport classes as shown in the tables below:

Physical Hazards

CLP class

Categories

TDG class

Packing groups

Notes

Explosives

Divisions 1.1 to 1.6

Class 1, Divisions 1.1 to 1.6

Not used

1

Flammable gases

1

Division 2.1

Not used

2

Not controlled

n/a

(chemically unstable gases)

A and B

Not covered

n/a

Aerosols (Flammable)

1, and 2

Division 2.1

Not used

2

3

Division 2.2

Not used

Oxidising gases

1

Division 2.2

Not used

Gases under pressure

1

Division 2.2

Not used

3

Flammable liquids

1

Class 3

PG I

2

PGII

3

PGIII

-

-

PGIII

4, 5, 6

Flammable solids

1

Class 4.1

PGII

2

PGIII

-

PGII, PGIII

7

Self-reactive

A to F

Class 4.1

A to F

8

Pyrophoric liquids

1

Class 4.2

Not used

Pyrophoric solids

1

Class 4.2

Not used

Self-heating

1

Class 4.2

PGII

2

PGIII

Chemicals which in contact with water emit flammable gases

1

Class 4.3

PGI

2

PGII

3

PGIII

Oxidising liquids

1

Class 5.1

PGI

2

PGII

3

PGIII

Oxidising solids

1

Class 5.1

PGI

2

PGII

3

PGIII

Organic peroxides

A to F

Class 5.2

A to F

Corrosive to metals

1

Class 8

PGIII

Health Hazards

CLP class

Categories

TDG class

Packing groups

Notes

Acute toxicity

1

Class 6.1

PGI

9

2

PGII

3

PGIII

4, 5

Not dangerous

n/a

10

Skin corrosion/irritation

1A

Class 8

PGI

11

1B

PGII

1C

PGIII

2

Not dangerous

n/a

Serious eye damage/irritation

1

Not dangerous

n/a

12

2

Respiratory or skin sensitisation

1 (or 1A or 1B)

Not dangerous

n/a

Germ cell mutagenicity

1A, 1B or 1C or 2

Not dangerous

n/a

13

Carcinogenicity

1A, 1B or 1C or 2

Not dangerous

n/a

13

Reproductive toxicity

1A, 1B or 1C or 2

Not dangerous

n/a

13

Specific Target Organ Toxicity — Single Exposure

1, 2, or 3

Not dangerous

n/a

Specific Target Organ Toxicity — Repeated Exposure

1 or 2

Not dangerous

n/a

Aspiration hazard

1

Not dangerous

n/a

Environmental Hazards

CLP class

Categories

TDG class

Packing groups

Notes

Acute aquatic toxicity

1

Class 9

PGIII

14

Chronic aquatic toxicity

1 or 2

PGIII

PGIII

3 or 4

Not dangerous

n/a

Hazardous to the ozone layer

1

Not dangerous

n/a

Notes

  1. Criteria are exactly the same.

  2. CLP has additional criteria for aerosols.

  3. Exemption if pressure < 200kpa at standard temperature and pressure (STP). Additionally, it should be noted that TDG also provides for classification of chemicals under pressure into Classes 2.1, 2.2, with or without subsidiary Class 6.1 or Class 8 health risks.

  4. Diesel, light heating oil and gas oils with FP above 60°C and up to 100°C is a special case under European inland transport rules, being controlled as dangerous good (possibly based on its environmental risk rather than its flammability risk). CLP permits these to be considered as CLP flammable liquid Category 3 when FP is between 60°C and 75°C.

  5. Transport Class 3 also includes liquid desensitised explosives, which are not yet part of the GHS system, and liquids with a flashpoint > 60°C but which are offered for carriage above their flashpoint.

  6. CLP does not control GHS flammable liquid Category 4.

  7. Transport also includes those liable to cause fire through friction, and solid desensitised explosives.

  8. Category G are not controlled by CLP or transport.

  9. Note that transport does not yet provide mixtures calculation system, and issues might be found due to CLP harmonised classification and labelling (CLH) decisions if it were to be included.

  10. Note GHS also has a Category 5 — which is not controlled by either CLP or Transport.

  11. Based on test result classifications only — see below regarding the Class 8 issue for mixtures and substances with assigned EU CLH for corrosion.

  12. Note that confusingly CLP uses the GHS05 pictogram with the corrosive symbol, which under Article 33 must appear therefore on the outside of the package or overpackage — but the H statement H318 (Causes serious eye damage) will show that the effect is only on the eye, and thus that the goods are not dangerous for transport for this hazard.

  13. Former confusion when the EU Directives (as implemented in the UK by the CHIP) would have required the toxic symbol on the outside of the packages, is now avoided due to the new GHS08 pictogram being specified.

  14. GHS, but not CLP has acute aquatic Category 2 and 3 hazards as well. Under CLP Category 3 or 4 does not attract the GHS09 pictogram with dead fish and tree symbol.

So as can be seen there is a tremendous degree of equivalence between GHS categories and packing groups or other divisions of classes where packing groups are not used. So why do some say that there is no equivalence? The issue really resolves around Class 8.

The Class 8 issue

When it came to amending the transport rules to introduce the GHS mixtures rules for skin corrosives, a number of issues arose when trying to classify using criteria other than that based on data from actual product testing.

For supply though there are categories 1A, 1B and 1C assignable, for CLP labelling there is no differentiation between being a Category 1A or Category 1B, but for transport the implications of being a PG1, PGII, or PGIII can be quite substantial.

Also when the EU decided to translate the EU CLH decisions that were taken under the former Dangerous Substances Directive 67/548/EEC (DSD) two category scheme into the new GHS based CLP three category scheme, since it did not matter for supply they chose to default to the lowest (higher hazard level) category (1A).

For example, for sodium hydroxide (NaOH) which had a DSD classification of C: R35 this was translated into Skin Corr.1A

However, moving NaOH from PGII to a PGI would have had a massive impact — eg not permitting NaOH, which had for years been safely transported in tanks, from being in those tanks any longer (if the logic in the UN Guiding Principles was to continue to be observed).

So this problem for Class 8 mixtures, in Europe, led to many people saying that there was no correlation and the myth once started, has oft been repeated.

Conclusion

So in general the GHS (CLP) Class categories do differentiate levels of hazard, which is something that transport PGs also do, and in general there is a tie up between CLP categories and TDG PGs, though admittedly not a directly numerical link.