The meaning of special waste is defined in Regulation 2 of The Special Waste Regulations 1996 (as amended) ('SWR96').

A desktop approach can be undertaken when trying to identify whether a waste is a special waste or not using the definition in SWR96:

Preliminary questions need to be asked to determine whether the substance is covered by the SWR96:

• Is the waste controlled waste? - SWR96 only applies to controlled waste (household, commercial and industrial waste)

• Is the waste household waste? - SWR96 excludes household waste that is not asbestos

• Is the waste a prescription only medicine? - these are all generically classified as special

For the purposes of this query, the assumption is that the waste is controlled waste but not household waste or a prescription only medicine.

The next steps require a closer examination of the nature of the waste by reference to its hazardous properties:

Does the waste contain a substance(s) Listed on the Approved Supply List?

The Approved Supply List (ASL) provides a risk phrase and classification for substances listed. This should be used to classify the hazard of each substance in the waste by looking up the substance in the alphabetic listing in the ASL - Part 1. The classification is given as a risk phrase(s) that can be linked to the hazardous properties in the SWR96

If no entry is found in the ASL, then further research is required using other data sources.

If the waste itself possesses a flash point less than 21ºC then it is a Special Waste by virtue of the hazardous property H3A (first indent).

If a substance(s) in the waste possess any of the hazardous properties, H4 to H8, then their concentration in the waste should be compared with the threshold concentrations given in Schedule 2, Part 111 to SWR96.

If the total concentration of these substance(s) in the waste with the same hazard or risk is equal to or greater than the threshold concentration then the waste is classified as a Special Waste.

If the waste is listed in Schedule 2, Part 1 of the SWR (as amended), then the waste must be further assessed against the other hazardous properties (H I, H2 H3A (other indents), H3B, H9 to H14).

The chemical formula for cobalt chloride is: CoCl₂

It also commonly exists in crystalline form as the hexahydrate: CoCl₂.6H₂O.

Cobalt dichloride is listed on the ASL 6th edition (HSE books, ISBN 0-7176-1832-3) as follows:

CAS: 007646-79-9

Index: 027-004-00-5

Class'n: Carc Cat 2: R49, Xn: R22, R42/43, N: R50, 53

Label: T, N

This entry does not specify which form of cobalt chloride this classification applies.

Cobalt Chloride is listed in DOSE (Royal Society of Chemistry, ISBN 0-85186-331-0) under entry C359.

It lists the following synonyms: cobalt dichloride and cobaltous chloride.

The entry also displays 2 CAS numbers for cobalt chloride: 7646-79-9 and 7791-13-1.

The latter entry is for the hexahydrate form.

Other pertinent information (for unspecified form of cobalt chloride):

Ecotox

LC₅₀(96hr) carp: 96mg/I

EC₅₀(48hr) daphnia: I.5mg/I

The hexahydrate: form of cobalt chloride is quoted in the above catalogue, pertinent information listed is:

CAS: 7791-13-1

Formula: CoCI₂.6H₂O

Risk phrases: R20/21/22 R36/37/38 R40

In addition, 'silica gel for desiccation' is also quoted in the above catalogue with the following information:

CAS: 112926-00-8

Risk phrases: R20 R36/37

The SWR96 are clear in that the classification of a waste containing a substance on the Approved Supply List must be used to determine the appropriate risk phrases to accommodate in the assessment methodology when considering whether the waste is a special waste.

From the above data, it can be seen that cobalt chloride and cobalt dichloride are the same. Therefore, using the ASL information, the limiting factor when considering whether a waste containing cobalt chloride is special will be the hazard carcinogenic (H7), which has a threshold of 0.1% w/w.

However, the above evidence highlights that there are distinctive forms of cobalt chloride, each with unique CAS numbers, which should be considered. Using the data from the Sigma catalogue it is clear that the hexahydrate crystalline form of cobalt chloride does not have the same CAS number as the substance quoted on the ASL, therefore, should be considered separately. The limiting threshold would be the based on the hazard irritant (H4) and has a threshold of 20% w/w.

For silica gel, the sigma catalogue provides data that indicates that the substance is harmful (H5) and irritant (H4). The limiting threshold would be the based on the hazard irritant and is 20% w/w.

Recommendation

Where the waste is quoted as containing the hexahydrate form of cobalt chloride, or cobalt dichloride hexahydrate or cobaltous chloride hexahydrate the waste will be special (on the basis of CoCl₂.6H₂O content only) if the substance is present at greater than or equal to 20% in the waste. This is taking into account information that the substance on the ASL is not the hexahydrate form.

Where the waste is quoted as containing the anhydrous form of cobalt chloride (or anhydrous cobalt dichloride or anhydrous cobaltous chloride) the waste will be special (on the basis of CoCl₂ content only) if the substance is present at greater than or equal to 0.1% in the waste.

Where the waste is quoted as containing an unspecified form of cobalt chloride we must assume worst case until proven otherwise and the waste will be special (on the basis of CoCl₂ content only) if the substance is present at greater than or equal to 0.1% in the waste.

Where the waste is quoted as containing silica gel the waste will be special (on the basis of silica gel content only) if the substance is present at greater than or equal to 20% in the waste.