Spent liquor from alkaline pulping and bleaching containing spent inorganic process chemicals and dissolved organic substances originating from the cellulosic raw material.

Endpoint summary

Description of key information

- Acute oral toxicity (LD50) of Black liquor is estimated to be > 2635 mg/kg (dwt.) body weight (> 5000 mg/kg (wwt.) body weight) (EC440/2008, B.1 tris, OECD 423, Annex 2c).
- According to the CLP regulation 1272/2008 and Commission Directive 2001/59/EC the test results of Black liquor do not indicate need for classification for acute oral toxicity.
- There is no available information of acute dermal or inhalation toxicity of Black liquor. Based on the main identified ingredients in Black liquor, no acute dermal toxicity is allocated according to the CLP rules, but the DSD/DPD rules suggest classification as R21: Harmful in contact with skin. 
- Toxic H2S gas can be liberated from Black liquor in contact with acids.

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion

Value:

mg/kg bw

Acute toxicity: via dermal route

Endpoint conclusion

Value:

mg/kg bw

Additional information

Black liquor did not show acute oral toxicity in a test performed according to the Test Guideline B.1 of the EC Regulation No 440/2008 (LD50 > 2635 mg/kg (substance dry weight) per body weight (> 5000 g/kg substance wet weight per body weight).

The expected maximum concentration ranges of the identified main components in Black liquor that hold a harmonized CLP classification, did not suggest acute oral toxicity of Black liquor either.

There is no available data on acute dermal toxicity of Black liquor. Of the identified main components of Black liquor only sodium sulfide (EC 215-211-5) has a harmonized CLP classification of Acute Tox.3 via dermal route. Based on the maximum expected concentration of Na₂S (10% w/w) in Black liquor, and CLP rules for classification, acute dermal toxicity class is not allocated.  According to the classification rules given under the DSD system, the Na₂S concentration suggests classification as Xn: R21 Harmful in contact with skin.

There is no available data concerning acute inhalation toxicity of Black liquor.

Justification for classification or non-classification

Black liquor is the spent cooking liquor from alkaline pulping and bleaching process. The source materials for Black liquor are softwood, hardwood, agricultural fibres and White liquor. Dry substance content of Black liquor varies from 3 to 80% consisting of ca.30 -77% of inorganics and 23-70% organics.

Black liquor is a UVCB substance with a fluctuating composition.Therefore the toxicological properties may be somewhat variable.

The toxicological properties (Annex VII, REACH regulation) of a representative Black liquor sample were tested by the Seibersdorf Labor GLP laboratory during 2009-2010 (the Key studies).

No data was found for the other toxicological endpoints, other than those referred in the endpoint records, through extensive literature searches. Black liquor is registered as a Transported Isolated Intermediate and no testing outside Annex VII in the REACH regulation is required.

According to the experimental results the acute toxic properties of Black liquor were:

- No need for acute oral classification (LD50 > 2635 mg/kg body weight (acute oral rat)).

Additionally, the need for classification according to the CLP and DSD/DPD rules was evaluated based on the expected maximum concentration of the identified main ingredient reported in the Black liquor typical composition (1.2), which holds a harmonized classification for acute toxicity (sodium sulfide, EC 215-211-5).

 

According to the main ingredients the toxic properties of Black liquor were:

- Non-toxic or Harmful (acute dermal).

None of the identified main ingredients hold a harmonized classification for any long-term toxicological impacts, and no classification is suggested due to the lack of experimental data.

 

The proposed classification derived from the experimental results and the properties of the main ingredients of Black liquor is:

 

CLP:             None    

DSD/DPD:    Xn: Harmful (Harmful in contact with skin)

                     

Supplemental hazard information:

In contact with acids Black liquor may release hydrogen sulfide gas (EC 231-977-3), which carries the harmonized classification Acute tox. 2 for inhalation. Therefore the hazard statements H330/R23 (Fatal if inhaled) and EUH032/R32 (Contact with acids liberates very toxic gas) are deemed necessary.