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

Toxicological Summary

Workers - Hazard via inhalation route

Systemic effects

Acute/short term exposure

DNEL related information

Local effects

Acute/short term exposure

DNEL related information

Workers - Hazard via dermal route

Systemic effects

Acute/short term exposure

DNEL related information

Additional information - workers

Black liquor is registered as a transported isolated intermediate and is manufactured and consumed under strictly controlled conditions during its whole life cycle. The estimation of systemic and local effects and derivation of DN(M)ELs is required for the chemical safety assessment (CSA) of substances manufactured/imported/used in quantities from 10 t/y onwards. CSA does not need to be performed for transported isolated intermediates.

Only few published investigations of the toxicity of Black liquor were available according to a literature search.Tthe toxicological information is based on the Key studies of a representative sample of Black liquor, conducted by Seibersdorf Labor GLP laboratory during 2009 -2010, and on the information on the maximum expected concentrations of the identified main components in Black liquor holding a harmonised classification.

Acute toxity, oral:

In the Key study for Acute oral toxicity in rats exposed to Black liquor (EC440/2008, B.1), no toxic effects of the test substance were noted by signs in life and post mortem at the dose of 2000 mg test substance per kg body weight. No mortality occurred. As no animals died, LD50oral was determined to be >2000 mg/kg (wwt.) body weight. Based on the guidance given in OECD guideline 423 (annex 2c), the LD50oral can be estimated to be > 2635 mg/kg (dwt.) body weight (>5000 mg/kg (wwt.) body weight, the tested sample contained 47.3 % water/52.7% dry solids).

Determination of pH and alkaline reserve:

The pH of a 10 % (w/w) aqueous solution of Black liquor was 12.35 which is higher than 11.5, and thus the alkaline reserve was determined. The pH + 1/12 alkaline reserve was 12.60, which is below the threshold of 14.5 for classification as corrosive and the pH + 1/6 alkaline reserve was 13.04 which is above the threshold of 13 for classification as irritant.

Skin irritation/corrosion:

Skin corrosion and irritation tests have been conducted to Black liquor in vitro (EC 440/2008, B.40 BIS).

Epiderm Skin Corrosivity Test, Experiment A.

Assay acceptance criteria according to the protocol INVITTOX n°119 by ECVAM:

-The mean percentage viability of the treated skin discs after 3 minutes of exposure was 94.5 % which is above the threshold of 50 % for classification.

- The mean percentage viability of the treated skin discs after 1 hour of exposure was 40.6 % which is above the threshold of 15 % for classification.

Epiderm Skin Corrosivity Test, Experiment B.

Assay acceptance criteria according to the protocol INVITTOX n°119 by ECVAM:

-The mean percentage viability of the treated skin discs after 3 minutes of exposure was 92.6 % which is above the threshold of 50 % for classification.

-The mean percentage viability of the treated skin discs after 1 hour of exposure was 30.7 % which is above the threshold of 15 % for classification.

To summarize the results on skin irritaition/corrosion, Black liquor shall be considered as irritant but non-corrosive according to the Test guideline (EC 440/2008, B.40 BIS). 

Eye Irritation:

Eye irritation was tested according to the OECD 437 BCOP test (Bovine Corneal Opacity and Permeability Test Method for Identifying Ocular Corrosives and Severe Irritants). According to the test results the IVIS of Black liquor was 268.2 and an important increase in opacity as well as in permeability was observed. Thus Black liquor is regarded to be an ocular corrosive or severe irritant. According to the results of this study and the Directive 2001/59/EC for classification, the test substance "Black liquor" needs to be labelled as R41 (EU DSD), Category 1 (GHS/CLP).

Genetic toxicity in vitro:

According to the bacterial mutagenicity test results (Ames test with Salmonella typhimurium) with and without metabolic activation, Black liquor did not show any mutagenic activity. A corresponding finding was obtained in a supporting study ragarding mutagenic properties with Spent pulpin liquors.

Other:

Some accidental incidences caused by Black liquor have been described.In these cases a combination of alkali/thermal burns resulting in hazardous effects on skin and eyes were detected.

According to the article Black liquor (pH 11-13) is used typically at a temperature of 85-95 ºC placing workers at risk to a combination of thermal and chemical burn.

General Population - Hazard via inhalation route

Systemic effects

Acute/short term exposure

DNEL related information

Local effects

Acute/short term exposure

DNEL related information

General Population - Hazard via dermal route

Systemic effects

Acute/short term exposure

DNEL related information

General Population - Hazard via oral route

Systemic effects

Acute/short term exposure

DNEL related information

Additional information - General Population

Black liquor is registered as a transported isolated intermediate and is manufactured and consumed under strictly controlled conditions during its whole life cycle. The systemic and local effects and derivation of DN(M)ELs is required for the chemical safety assessment (CSA) of substances manufactured/imported/used in quantities from 10 t/y onwards. CSA does not need to be performed for transported isolated intermediates.