Registration Dossier

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:
DNEL (Derived No Effect Level)
Value:
1 mg/m³
Most sensitive endpoint:
irritation (respiratory tract)
DNEL related information
DNEL derivation method:
ECHA REACH Guidance
Overall assessment factor (AF):
1
Dose descriptor:
NOAEC
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
DNEL derivation method:
ECHA REACH Guidance

Local effects

Long term exposure
Hazard assessment conclusion:
no hazard identified
DNEL related information
DNEL derivation method:
ECHA REACH Guidance
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

Sodium Hydride reacts with water to produce hydrogen gas and sodium hydroxide. As such it is not possible to test this substance (data waived according to Annex XI, part 2 of the REACH text). However, due to the formation of sodium hydroxide it is possible to assess (to a limited extent) the human health hazards associated with the degradation product rather than the parent compound.

The focus is the occurence 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) (see Table 1). 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.

Table 25. Occupational Exposure Limits (OELs) in the EU and Norway (ACGIH, 2006)

EU Member State

Unit

TW

ST

Ceiling

Reference

Austria

mg/m3

2

4

 

 

Belgium

mg/m3

 

 

2

ACGIH, 2006

Czech Republic

mg/m3

1

2

 

ACGIH, 2006

Denmark

mg/m3

2

 

 

 

Finland

mg/m3

2

 

 

ACGIH, 2006

France

mg/m3

2

 

 

 

Hungary

mg/m3

2

2

 

 

Ireland

mg/m3

 

2

 

ACGIH, 2006

Norway

mg/m3

 

 

2

ACGIH, 2006

Poland

mg/m3

0.5

1

 

ACGIH, 2006

Portugal

mg/m3

 

2

 

 

Spain

mg/m3

 

2

 

ACGIH, 2006

Sweden

mg/m3

1

 

2

ACGIH, 2006

United Kingdom

mg/m3

 

2

 

ACGIH, 2006

General Population - Hazard via inhalation route

Systemic effects

Long term exposure
Hazard assessment conclusion:
no hazard identified
DNEL related information
DNEL derivation method:
ECHA REACH Guidance
Acute/short term exposure
Hazard assessment conclusion:
no hazard identified
DNEL related information
DNEL derivation method:
ECHA REACH Guidance

Local effects

Long term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
1 mg/m³
Most sensitive endpoint:
irritation (respiratory tract)
DNEL related information
DNEL derivation method:
ECHA REACH Guidance
Overall assessment factor (AF):
1
Dose descriptor:
NOAEC
Acute/short term exposure
Hazard assessment conclusion:
no hazard identified
DNEL related information
DNEL derivation method:
ECHA REACH Guidance

General Population - Hazard via dermal route

Systemic effects

Long term exposure
Hazard assessment conclusion:
no hazard identified
DNEL related information
DNEL derivation method:
ECHA REACH Guidance
Acute/short term exposure
Hazard assessment conclusion:
no hazard identified
DNEL related information
DNEL derivation method:
ECHA REACH Guidance

Local effects

Long term exposure
Hazard assessment conclusion:
no hazard identified
DNEL related information
DNEL derivation method:
ECHA REACH Guidance
Acute/short term exposure
Hazard assessment conclusion:
no hazard identified
DNEL related information
DNEL derivation method:
ECHA REACH Guidance

General Population - Hazard via oral route

Systemic effects

Long term exposure
Hazard assessment conclusion:
no hazard identified
DNEL related information
DNEL derivation method:
ECHA REACH Guidance
Acute/short term exposure
Hazard assessment conclusion:
no hazard identified
DNEL related information
DNEL derivation method:
ECHA REACH Guidance

General Population - Hazard for the eyes

Local effects

Hazard assessment conclusion:
no hazard identified

Additional information - General Population

Sodium Hydride reacts with water to produce hydrogen gas and sodium hydroxide. As such it is not possible to test this substance (data waived according to Annex XI, part 2 of the REACH text). However, due to the formation of sodium hydroxide it is possible to assess (to a limited extent) the human health hazards associated with the degradation product rather than the parent compound.

As sodium hydroxide is not expected to become systemically available in the body under normal handling and use conditions, the focus is on possible risks from acute exposure (local effects) (EU RAR of Sodium Hydroxide, 2007; section 4.1.3.2.4.1; page 77).

Acute exposure

Acute / short-term exposure and long-term exposure - systemic effects

As sodium hydroxide is not expected to become systemically available in the body under normal handling and use conditions, the focus is on possible risks from acute exposure (local effects) (EU RAR of Sodium Hydroxide, 2007; section 4.1.3.2.4.1; page 77).

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 dermal toxicity.

Long-term exposure

DNEL - long term exposure - local effects - dermal:

No DNEL long-term exposure - local effects could be derived as no reliable dose descriptors were available for that route of exposure.

DNEL - long term exposure - local effects - inhalation

The same point of departure is relevant for deriving a DNEL for the general population, i.e. the study by Fritschi et al (2001). The following comments apply in the assessment of the need for further Assessment Factors in deriving a local DNEL for the general population.

1. The assessment of exposure to sodium hydroxide conducted by Fritschi et al was based on peak exposures over a 15-minute period. The same assessment of duration of exposure would be relevant for both the working population and the general population, given that the effect being assessed to dereive the NOAEL is local irritation of the respiratory tract. No further modification is therefore required to the NOAEL to take account of potential differences in the duration of exposure of the general population.

2. In the population studied by Fritschi et al, in excess of 40% of the 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 and, as such, could be regarded as an adequate representation of the general population in terms of their response to sodium hydroxide. It is concluded, therefore, that no additional assessment factor is required to take account of further intraspecies differences in the general human population.

As a result, the DNEL for sodium hydroxide for long-term inhalation, general population = 1.0 mg/m³.