Reaction mass of disodium sulphide and sodium carbonate and sodium hydrogensulphide

Toxicological Summary

Workers - Hazard via inhalation route

Systemic effects

Long term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

22.6 mg/m³

Most sensitive endpoint:

repeated dose toxicity

DNEL related information

Overall assessment factor (AF):

15

Modified dose descriptor starting point:

NOAEC

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

DNEL related information

Local effects

Long term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

2.84 mg/m³

Most sensitive endpoint:

repeated dose toxicity

DNEL related information

Overall assessment factor (AF):

15

Dose descriptor:

NOAEC

Acute/short term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

5.682 mg/m³

DNEL related information

DNEL extrapolated from long term DNEL

Workers - Hazard via dermal route

Systemic effects

Long term exposure

Hazard assessment conclusion:

medium hazard (no threshold derived)

Acute/short term exposure

Hazard assessment conclusion:

medium hazard (no threshold derived)

DNEL related information

Local effects

Long term exposure

Hazard assessment conclusion:

medium hazard (no threshold derived)

Acute/short term exposure

Hazard assessment conclusion:

medium hazard (no threshold derived)

Workers - Hazard for the eyes

Local effects

Hazard assessment conclusion:

high hazard (no threshold derived)

Additional information - workers

The derivation of DNELs is described in detail in the CSR.

In brief, no DNEL was derived for any dermal exposure to scrubber liquid since it is classified as corrosive by considerations based on the pH value > 11.5 for two of its constituents. For workers a qualitative approach is required based on the corrosive potential of sodium hydrogensulphide and sodium sulphide.

 Assessment of oral exposure DNELs for workers is not required in accordance with ECHA guidance.

 A DNEL for acute exposure, systemic effects by inhalation was not derived, because there is no reason of concern for systemic toxicity with respect to acute inhalation, since high exposure levels which are not covered by the long-term DNEL are not expected.

 A long-term DNEL, systemic effects by inhalation was derived for workers, because there is a potential for exposure via the inhalation route at the workplace. The DNEL is based on the results of a repeated dose inhalation study with dihydrogen sulphide in which some minor effects on food consumption and body weight were observed, but exposure up to the highest does of 80 ppm H2S did not result in toxicologically relevant alterations in haematological indices, serum chemistry, or gross pathology. Therefore, the concentration of 80 ppm H₂S (111 mg/m³) is considered as NOAEC for systemic effects.

 Long-term DNEL, local effects by inhalation: From the repeated dose study on H2S inhalation, a NOAEC of 10 ppm H₂S for local effects was derived which is based on an increased incidence of olfactory neuronal loss (ONL) at 30 and 80 ppm of hydrogen sulfide. Due to the lack of experimental data specifically for sodium hydrogensulphide, read-across from data with H₂S was regarded as appropriate. Considering local effects in the respiratory tract related to inhalation exposure to sodium hydrogensulphide, two mechanisms of toxicity can be assumed: the first mechanism can be related to the local effects of HS^-present in the respiratory tract (ONL) following exposure to sulphides, and the second effects can be attributed to the very high pH resulting from the presence of OH^-ions. In order to cover both effects, DNELs were derived based on the NOAEC for local effects of H₂S, and in addition the DNEL for NaOH. As a precautionary principle, the lower value for sodium hydrogensulphide was selected as DNEL for local effects.

 Acute DNEL, local effects by inhalation: Sodium hydrogensulphide is classified as corrosive by default. Therefore, and in accordance to the ECHA guidance on information requirements and chemical safety assessment – chapter R.8: Characterisation of dose [concentration]-response for human health, May 2008 a DNEL for acute inhalation toxicity should be derived based on the toxicological profile of the substance concerned. This should be derived for a specified fraction of the daily exposure duration (usually 15 minutes for workers). SCOEL recommendations exist for H2SO4, HCL, H3PO4 and F2, all of which are classified either as R34 or R35 and without doubt have a higher corrosive potential compared to Na2S. The above mentioned documents all mention an 8-hour TWA as well as an STEL for 15 minutes. All STEL values are merely derived by applying a factor of 2 to the 8 hour TWA. Based on the toxicological observations as summarised in these SCOEL documents, a factor of 2 for the extrapolation from the long-term DNEL to an acute DNEL should be appropriate. Hence the DNEL for long-term inhalation, local effects will be used for deriving a DNEL for acute inhalation effect, worker by multiplying the long-term DNEL with a factor of 2. The long-term DNEL for local effects in workers exposed by inhalation for scrubber liquid is 2.84 mg/m3, corresponding to a STEL (15 min) for workers of 5.68 mg/m3.

General Population - Hazard via inhalation route

Systemic effects

Long term exposure

Hazard assessment conclusion:

hazard unknown but no further hazard information necessary as no exposure expected

Acute/short term exposure

Hazard assessment conclusion:

hazard unknown but no further hazard information necessary as no exposure expected

DNEL related information

Local effects

Long term exposure

Hazard assessment conclusion:

hazard unknown but no further hazard information necessary as no exposure expected

Acute/short term exposure

Hazard assessment conclusion:

hazard unknown but no further hazard information necessary as no exposure expected

DNEL related information

General Population - Hazard via dermal route

Systemic effects

Long term exposure

Hazard assessment conclusion:

hazard unknown but no further hazard information necessary as no exposure expected

Acute/short term exposure

Hazard assessment conclusion:

hazard unknown but no further hazard information necessary as no exposure expected

DNEL related information

Local effects

Long term exposure

Hazard assessment conclusion:

hazard unknown but no further hazard information necessary as no exposure expected

Acute/short term exposure

Hazard assessment conclusion:

hazard unknown but no further hazard information necessary as no exposure expected

General Population - Hazard via oral route

Systemic effects

Long term exposure

Hazard assessment conclusion:

hazard unknown but no further hazard information necessary as no exposure expected

Acute/short term exposure

Hazard assessment conclusion:

hazard unknown but no further hazard information necessary as no exposure expected

DNEL related information

General Population - Hazard for the eyes

Local effects

Hazard assessment conclusion:

hazard unknown but no further hazard information necessary as no exposure expected

Additional information - General Population

The derivation of DNELs for scrubber liquid was performed in the same manner as for the REACH registration of two of its constituents, sodium hydrogensulphide and sodium sulphide and is described in the CSR.

 In brief, exposure of the general population to sodium hydrogensulphide and sodium sulphide is of no concern for any route of exposure (oral, dermal, inhalation).Since sodium hydrogensulfide and sodium sulphide are instable and prone to oxidation in ambient air and used merely as intermediates and not in consumer products, there can neither be any quantitatively relevant emissions from industrial sites nor from use of sulfide-containing products. Therefore, for lack of consumer or indirect exposure, the derivation DNELs for the general population is not considered to be required.