Registration Dossier
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EC number: 212-974-6 | CAS number: 894-86-0
Toxicological Summary
Administrative data
Workers - Hazard via inhalation route
Systemic effects
Long term exposure
- Hazard assessment conclusion:
- no hazard identified
Acute/short term exposure
- Hazard assessment conclusion:
- no hazard identified
DNEL related information
Local effects
Long term exposure
- Hazard assessment conclusion:
- no hazard identified
Acute/short term exposure
- Hazard assessment conclusion:
- no hazard identified
DNEL related information
Workers - Hazard via dermal route
Systemic effects
Long term exposure
- Hazard assessment conclusion:
- no hazard identified
Acute/short term exposure
- Hazard assessment conclusion:
- no hazard identified
DNEL related information
Local effects
Long term exposure
- Hazard assessment conclusion:
- no hazard identified
Acute/short term exposure
- Hazard assessment conclusion:
- no hazard identified
Workers - Hazard for the eyes
Local effects
- Hazard assessment conclusion:
- no hazard identified
Additional information - workers
The test substance is synthesized and handled in an aqueous sodium hydroxide solution (pH 13) under inert gas atmosphere to avoid oxidation to indigo which is practically insoluble in water. It is instable in an aqueous phase at neutral pH or as solid material on air and oxidises rapidly to indigo (CAS number 482-89-3). The tests presented in the toxicity section are therefore either performed with preparations of leucoindigo or leucoindigo-salts which were prevented from oxidation or, in majority, with the oxidised substance, i.e., indigo. Risk assessment is therefore mainly based on the studies with indigo.
As no adverse effects were observed with either leucoindigo or indigo, no DNELs were derived for the registered substance in its theoretical solid sodium salt form. The only adverse effects observed were local effects due to sodium hydroxide, which was present in different formulations to prevent oxidation. Hence local irritation or corrosion due to the stabiliser sodium hydroxide can be expected.
For the Risk Assessment of sodium hydroxide (EC number 215-185-5) we refer to the registration for sodium hydroxide (REACH registration number 01-2119457892-27-0138). The following discussion for DNELs for NaOH is taken from the Toxicological Summary of the Lead Dossier EC number 215-185-5 provided by the Lead INOVYN France S.A.S..
The focus is the occurrence of local effects after acute and repeated exposure at those places where NaOH is produced and/or used. This is because NaOH is not expected to become systemically available in the body under normal handling and use conditions, i.e. neither the concentration of sodium in the blood nor the pH of the blood will be increased (EU RAR of sodium hydroxide, 2007; section 4.1.3.1, page 73).
Acute exposure
Acute / short-term exposure and long-term exposure - systemic effects
NaOH is not expected to become systemically available in the body under normal handling and use conditions, i.e. neither the concentration of sodium in the blood nor the pH of the blood will be increased (EU RAR of sodium hydroxide, 2007; section 4.1.3.1, page 73). Therefore, it is not useful to derive a DNEL for acute exposure, systemic effects.
Acute - short-term exposure - local effects (dermal)
According to the CLP Regulation No 1272/2008 Annex VI Table 3.1, the concentration limit for corrosivity of NaOH is considered to be 2%.
Acute - short-term exposure - local effects (inhalation)
According to chapter R8 of the ECHA "Guidance on information requirements and chemical safety assessment' a DNEL for acute toxicity should be derived if an acute toxicity hazard (leading to C&L) has been identified. Sodium hydroxide is not classified regarding acute inhalation toxicity. In addition, a DNEL for acute toxicity should be derived if there is a potential for high peak exposures, for instance when sampling or connecting/disconnecting vessels. This is not the case for sodium hydroxide. High peak exposure do not occur during the manufacturing or use.
Long-term exposure
Long-term exposure - local effects (dermal DNEL in mg/kg bw):
No DNEL long-term exposure - local effects could be derived as no reliable dose descriptors were available for that route of exposure.
Long-term exposure - local effects (inhalation DNEL in mg/m3):
The most relevant starting point from the available data is the study of Fritschi et al (2001), which is a cross-sectional survey of 2404 employees from three aluminium refineries. Of these subjects, 1045 had been exposed to sodium hydroxide mist, leaving 1553 unexposed subjects.
Exposure to sodium hydroxide mist had been assessed on a semi-quantitative basis and the exposed subjects had been assigned to one of three exposure groups: low (<0.05 mg/m3), medium (0.05 – 1.0 mg/m3) or high (>1.0 mg/m3) based on an assessment of peak exposures over a 15 -minute period. The authors concluded that exposure to high levels of sodium hydroxide mist (>1.0 mg/m3) was associated with an increased prevalence of reporting work-related wheeze and rhinitis, but not impairment of lung function. These symptomatic reports of respiratory tract irritation, in the lack of any measured functional change in lung performance, suggest that any effects were minimal. Such reporting is also subject to recall bias, which can lead to over-reporting of symptomatology. No increased prevalence of respiratory symptoms was reported for the subjects in the medium exposure group.
This data suggests that the NOEL for respiratory irritation due to exposure to sodium hydroxide mist in a large sample of subjects from three factories was 1.0 mg/m3. This value is likely to be a conservative estimate due to the study design.
As the study was conducted in human subjects, no interspecies assessment factor is required. Similarly, assessment factors to take account of differences in exposure duration, dose-response or quality of the database are not required. It is noted that in excess of 40% of the study subjects were reported to be atopic. This distribution suggests that the study population were towards the more sensitive end of the overall population in terms of their response to respiratory irritants. This fact, coupled with the fact that a relatively large random sample of workers had been studied, suggest also that no assessment factor is required to account for intraspecies differences in the human population.
In addition, it is noted that in many EU countries, the OEL (8-hour TWA) for sodium hydroxide is 2.0 mg/m³, with a few exceptions (Czech Republic - 1.0 mg/m3; Poland – 0.5 mg/m³). In the UK, a Workplace Exposure Limit (15-minute STEL) of 2.0 mg/m³ exists. This value is most probably based on the ACGIH TLV Ceiling Limit of 2.0 mg/m³, which itself is based on “noticeable, but not excessive, ocular and upper respiratory tract irritation” (ACGIH, 1997). This latter statement is attributed to Patty, 1947. These OEL values are broadly consistent with a NOEL in humans for respiratory irritation of 1.0 mg/m³.
1 mg/m3 is considered to be the NOEL for sodium hydroxide mist in humans for respiratory irritation For the reasons stated above, it is proposed that no assessment factors are required to derive the DNEL.
As a result, the DNEL for sodium hydroxide for long-term inhalation, workers = 1.0 mg/m³.
General Population - Hazard via inhalation route
Systemic effects
Long term exposure
- Hazard assessment conclusion:
- no hazard identified
Acute/short term exposure
- Hazard assessment conclusion:
- no hazard identified
DNEL related information
Local effects
Long term exposure
- Hazard assessment conclusion:
- no hazard identified
Acute/short term exposure
- Hazard assessment conclusion:
- no hazard identified
DNEL related information
General Population - Hazard via dermal route
Systemic effects
Long term exposure
- Hazard assessment conclusion:
- no hazard identified
Acute/short term exposure
- Hazard assessment conclusion:
- no hazard identified
DNEL related information
Local effects
Long term exposure
- Hazard assessment conclusion:
- no hazard identified
Acute/short term exposure
- Hazard assessment conclusion:
- no hazard identified
General Population - Hazard via oral route
Systemic effects
Long term exposure
- Hazard assessment conclusion:
- no hazard identified
Acute/short term exposure
- Hazard assessment conclusion:
- no hazard identified
DNEL related information
General Population - Hazard for the eyes
Local effects
- Hazard assessment conclusion:
- no hazard identified
Additional information - General Population
Indigo as defined by the sameness criteria did not show any adverse systemic or local effects either during short-term or long-term exposure. Hence, there is no hazard for the consumer during use of the respective articles.
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