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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

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
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

Local effects

Long term exposure
Hazard assessment conclusion:
high hazard (no threshold derived)
Acute/short term exposure
Hazard assessment conclusion:
high hazard (no threshold derived)

Workers - Hazard for the eyes

Local effects

Hazard assessment conclusion:
high hazard (no threshold derived)

Additional information - workers

Discussion DNEL for workers

The focus is the occurence of local effects after acute and repeated exposure at those places where KOH is produced and/or used. This is because KOH is not expected to become systemically available in the body under normal handling and use conditions, i.e. neither the concentration of potassium in the blood nor the pH of the blood will be increased (OECD SIDS KOH 2002). The same conclusion was reached for NaOH (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

KOH is not expected to become systemically available in the body under normal handling and use conditions, i.e. neither the concentration of potassium in the blood nor the pH of the blood will be increased (analoguous to NaOH in 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 KOH 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 there is a potential for high peak exposures, for instance when sampling or connecting/disconnecting vessels. This is not the case for potassium hydroxide. High peak exposure does 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 1359 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). 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 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 the OEL (8-hour TWA) for potassium hydroxide is 2.0 mg/m3, (Belgium, NIOSH, ACGIH) This OEL value is broadly consistent with a NOEL in humans for respiratory irritation of 1.0 mg/m3.

 

1 mg/m3is 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. One can read-across from NaOH to determine the DNEL for KOH because the hydroxyl ion is responsible for the respiratory irritation effects.

As a result, the DNEL for potassium hydroxide for long-term inhalation for workers is 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:
DNEL (Derived No Effect Level)
Value:
1 mg/m³
Most sensitive endpoint:
irritation (respiratory tract)
DNEL related information
Overall assessment factor (AF):
1
Dose descriptor:
NOAEC
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:
high hazard (no threshold derived)
Acute/short term exposure
Hazard assessment conclusion:
high hazard (no threshold derived)

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:
high hazard (no threshold derived)

Additional information - General Population

Discussion DNEL for general population

As potassium 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 potassium 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) (analoguous to 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 KOH is considered to be 2%. This value is taken forward to the risk characterisation as concentration limit for corrosivity.

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. Potassium hydroxide is not classified regarding acute inhalation 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

This DNEL is based on read-across data from sodium hydroxide, since potassium hydroxide is expected to have similar properties as sodium hydroxide.

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 long-term inhalation, general population = 1.0 mg/m³.