Registration Dossier
Registration Dossier
Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.
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EC number: 205-182-7 | CAS number: 135-19-3
Toxicological Summary
Administrative data
Workers - Hazard via inhalation route
Systemic effects
Long term exposure
- Hazard assessment conclusion:
- DNEL (Derived No Effect Level)
- Value:
- 1.76 mg/m³
- Most sensitive endpoint:
- repeated dose toxicity
- Route of original study:
- Oral
DNEL related information
- DNEL derivation method:
- ECHA REACH Guidance
- Overall assessment factor (AF):
- 75
- Dose descriptor starting point:
- NOAEL
- Value:
- 150 mg/kg bw/day
- Modified dose descriptor starting point:
- NOAEC
- Value:
- 134.24 mg/m³
- Explanation for the modification of the dose descriptor starting point:
Workers: As the NOAEL was obtained on rats using the oral route, it must be corrected for an inhalation exposure of workers, taking into account that workers are considered to be working 8h/d, with inhalative volumes for 8h/d defined in the ECHA Guidance at 6.7m3 for base level activity and 10m3 for light activity.
Corrected NOAEC(systemic-inhalation) = NOAEL(oral-rat) * (1 / sRV(rat)) * ((ABS(oral-rat) / ABS(inhalation-human))) * (sRV(human) / wRV)
Where ABS = Absorption, sRV = standard Respiratory Volume, and wRV = worker Respiratory Volume. Absorptions by inhalation and oral route are not known, therefore it was considered that oral absorption in the rat was 50% less effective than the human absorption by inhalation in accordance with ECHA Guidance.
Corrected NOAEC(systemic-inhalation) = NOAEL(oral-rat) * (1 / sRV(rat)) * ((ABS(oral-rat) / ABS(inhalation-human))) * (sRV(human) / wRV)
Corrected NOAEC(systemic-inhalation) = NOAEL(oral-rat) * (1 / sRV(rat)) * 0.5 * (sRV(human) / wRV)
Corrected NOAEC(systemic-inhalation) = 150 mg/kg bw * (1 / 0.38 m3/kg) * 0.5 * (6.7 m3 / 10 m3)
Corrected NOAEC(systemic-inhalation) = 132.24 mg/m3
- AF for dose response relationship:
- 1
- Justification:
- Default
- AF for differences in duration of exposure:
- 6
- Justification:
- Default
- AF for interspecies differences (allometric scaling):
- 1
- Justification:
- Default
- AF for other interspecies differences:
- 2.5
- Justification:
- Default
- AF for intraspecies differences:
- 5
- Justification:
- Default
- AF for the quality of the whole database:
- 1
- Justification:
- Default
Acute/short term exposure
- Hazard assessment conclusion:
- DNEL (Derived No Effect Level)
- Value:
- 36.2 mg/m³
- Most sensitive endpoint:
- acute toxicity
- Route of original study:
- By inhalation
DNEL related information
- DNEL derivation method:
- ECHA REACH Guidance
- Overall assessment factor (AF):
- 12.5
- Dose descriptor starting point:
- NOAEC
- Value:
- 900 mg/m³
- Modified dose descriptor starting point:
- NOAEC
- Value:
- 452.25 mg/m³
- Explanation for the modification of the dose descriptor starting point:
Workers: As the NOAEC was obtained on rats exposed 4h to the substance, it must be corrected for an inhalation exposure of workers, taking into account that workers are considered to be working 8h/d, with inhalative volumes for 8h/d defined in the ECHA Guidance at 6.7m3 for base level activity and 10m3 for light activity.
Corrected NOAEC(inhalation) = NOAEC(inhalation) * (exp.cond.rat / exp.cond.human)
Corrected NOAEC(inhalation) = 900 mg/m3 * (6 h/d / 8 h/d ) * (6.7 m3 / 10 m3)
Corrected NOAEC(inhalation) = 452.25 mg/m3
- AF for dose response relationship:
- 1
- Justification:
- Default
- AF for interspecies differences (allometric scaling):
- 1
- Justification:
- default
- AF for other interspecies differences:
- 2.5
- Justification:
- default
- AF for intraspecies differences:
- 5
- Justification:
- default
- AF for the quality of the whole database:
- 1
- Justification:
- default
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)
DNEL related information
Workers - Hazard via dermal route
Systemic effects
Long term exposure
- Hazard assessment conclusion:
- DNEL (Derived No Effect Level)
- Value:
- 1 mg/kg bw/day
- Most sensitive endpoint:
- repeated dose toxicity
- Route of original study:
- Oral
DNEL related information
- DNEL derivation method:
- ECHA REACH Guidance
- Overall assessment factor (AF):
- 300
- Dose descriptor starting point:
- NOAEL
- Value:
- 150 mg/kg bw/day
- Modified dose descriptor starting point:
- NOAEL
- Value:
- 300 mg/kg bw/day
- Explanation for the modification of the dose descriptor starting point:
As reported in the OECD SID report for 2-Naphthol, the substance can be absorbed through the skin. Rapid conjugation with glucuronide and sulphate in the liver and renal excretion of the unchanged and conjugated forms seems to be the principal mechanism of elimination.
In humans, absorption through the skin was demonstrated following the use of 2-naphthol in a peeling paste for the treatment of acne. About 5 % of the applied dose (7.5 g paste containing 20 % 2-naphthol) was recovered after 24 hours in the urine.
2-Naphthol is a solid, and has an average particle size of 3011 μm. According to
the literature, particles that have a size of >45 nm are unlikely to penetrate nor permeate the skin.2. Furthermore, the octanol/water partition coefficient of 2-naphthol is 1.89. This suggests that 2-naphthol has a low lipophilicity and therefore a low rate of absorption can be expected. Although moisture on the skin will increase the dermal
absorption of substances.Based on the physical properties of 2 naphthol and available data relating to dermal absorption the dose descriptor for dermal exposure has been modified. A conservative estimate of dermal absorption of 50% has been applied.
- AF for dose response relationship:
- 1
- Justification:
- Default (DNEL calculator)
- AF for differences in duration of exposure:
- 6
- Justification:
- Default
- AF for interspecies differences (allometric scaling):
- 4
- Justification:
- Default
- AF for other interspecies differences:
- 2.5
- Justification:
- Default
- AF for intraspecies differences:
- 5
- Justification:
- Default
- AF for the quality of the whole database:
- 1
- Justification:
- Default
Acute/short term exposure
- Hazard assessment conclusion:
- DNEL (Derived No Effect Level)
- Value:
- 3 mg/kg bw/day
- Most sensitive endpoint:
- repeated dose toxicity
- Route of original study:
- Oral
DNEL related information
- DNEL derivation method:
- ECHA REACH Guidance
- Overall assessment factor (AF):
- 50
- DNEL extrapolated from long term DNEL
- Dose descriptor starting point:
- NOAEL
- Value:
- 150 mg/m³
- Modified dose descriptor starting point:
- NOAEL
- Value:
- 300 mg/kg bw/day
- Explanation for the modification of the dose descriptor starting point:
As reported in the OECD SID report for 2-Naphthol, the substance can be absorbed through the skin. Rapid conjugation with glucuronide and sulphate in the liver and renal excretion of the unchanged and conjugated forms seems to be the principal mechanism of elimination.
In humans, absorption through the skin was demonstrated following the use of 2-naphthol in a peeling paste for the treatment of acne. About 5 % of the applied dose (7.5 g paste containing 20 % 2-naphthol) was recovered after 24 hours in the urine.
2-Naphthol is a solid, and has an average particle size of 3011 μm. According to
the literature, particles that have a size of >45 nm are unlikely to penetrate nor permeate the skin.2. Furthermore, the octanol/water partition coefficient of 2-naphthol is 1.89. This suggests that 2-naphthol has a low lipophilicity and therefore a low rate of absorption can be expected. Although moisture on the skin will increase the dermal
absorption of substances.Based on the physical properties of 2 naphthol and available data relating to dermal absorption the dose descriptor for dermal exposure has been modified. A conservative estimate of dermal absorption of 50% has been applied.
- AF for dose response relationship:
- 1
- Justification:
- Default
- AF for interspecies differences (allometric scaling):
- 4
- Justification:
- Default
- AF for other interspecies differences:
- 2.5
- Justification:
- Default
- AF for intraspecies differences:
- 5
- Justification:
- Default
- AF for the quality of the whole database:
- 1
- Justification:
- Default
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
General Population - Hazard via inhalation route
Systemic effects
Long term exposure
- Hazard assessment conclusion:
- DNEL (Derived No Effect Level)
- Value:
- 0.435 mg/m³
- Most sensitive endpoint:
- repeated dose toxicity
- Route of original study:
- Oral
DNEL related information
- DNEL derivation method:
- ECHA REACH Guidance
- Overall assessment factor (AF):
- 150
- Dose descriptor starting point:
- NOAEL
- Value:
- 150 mg/kg bw/day
- Value:
- 65.3 mg/m³
- Explanation for the modification of the dose descriptor starting point:
Default (DNEL calculator)
- AF for dose response relationship:
- 1
- Justification:
- Default (DNEL calculator)
- AF for differences in duration of exposure:
- 6
- Justification:
- Default (DNEL calculator)
- AF for interspecies differences (allometric scaling):
- 1
- Justification:
- Default (DNEL calculator)
- AF for other interspecies differences:
- 2.5
- Justification:
- Default (DNEL calculator)
- AF for intraspecies differences:
- 10
- Justification:
- Default (DNEL calculator)
- AF for the quality of the whole database:
- 1
- Justification:
- Default (DNEL calculator)
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:
- high hazard (no threshold derived)
Acute/short term exposure
- Hazard assessment conclusion:
- high hazard (no threshold derived)
DNEL related information
General Population - Hazard via dermal route
Systemic effects
Long term exposure
- Hazard assessment conclusion:
- DNEL (Derived No Effect Level)
- Value:
- 0.5 mg/kg bw/day
- Most sensitive endpoint:
- repeated dose toxicity
- Route of original study:
- Oral
DNEL related information
- DNEL derivation method:
- ECHA REACH Guidance
- Overall assessment factor (AF):
- 600
- Dose descriptor starting point:
- NOAEL
- Value:
- 150 mg/kg bw/day
- Modified dose descriptor starting point:
- NOAEL
- Value:
- 300 mg/kg bw/day
- Explanation for the modification of the dose descriptor starting point:
As reported in the OECD SID report for 2-Naphthol, the substance can be absorbed through the skin. Rapid conjugation with glucuronide and sulphate in the liver and renal excretion of the unchanged and conjugated forms seems to be the principal mechanism of elimination.
In humans, absorption through the skin was demonstrated following the use of 2-naphthol in a peeling paste for the treatment of acne. About 5 % of the applied dose (7.5 g paste containing 20 % 2-naphthol) was recovered after 24 hours in the urine.
2-Naphthol is a solid, and has an average particle size of 3011 μm. According to
the literature, particles that have a size of >45 nm are unlikely to penetrate nor permeate the skin.2. Furthermore, the octanol/water partition coefficient of 2-naphthol is 1.89. This suggests that 2-naphthol has a low lipophilicity and therefore a low rate of absorption can be expected. Although moisture on the skin will increase the dermal
absorption of substances.Based on the physical properties of 2 naphthol and available data relating to dermal absorption the dose descriptor for dermal exposure has been modified. A conservative estimate of dermal absorption of 50% has been applied.
- AF for dose response relationship:
- 1
- Justification:
- Default (DNEL calculator)
- AF for differences in duration of exposure:
- 6
- Justification:
- Default (DNEL calculator)
- AF for interspecies differences (allometric scaling):
- 4
- Justification:
- Default (DNEL calculator)
- AF for other interspecies differences:
- 2.5
- Justification:
- Default (DNEL calculator)
- AF for intraspecies differences:
- 10
- Justification:
- Default (DNEL calculator)
- AF for the quality of the whole database:
- 1
- Justification:
- Default (DNEL calculator)
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:
- 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:
- DNEL (Derived No Effect Level)
- Value:
- 0.25 mg/kg bw/day
- Most sensitive endpoint:
- repeated dose toxicity
- Route of original study:
- Oral
DNEL related information
- DNEL derivation method:
- ECHA REACH Guidance
- Overall assessment factor (AF):
- 600
- Dose descriptor starting point:
- NOAEL
- Value:
- 150 mg/kg bw/day
- Value:
- 150 mg/kg bw/day
- Explanation for the modification of the dose descriptor starting point:
Default (DNEL calculator)
- AF for dose response relationship:
- 1
- Justification:
- Default (DNEL calculator)
- AF for differences in duration of exposure:
- 6
- Justification:
- Default (DNEL calculator)
- AF for interspecies differences (allometric scaling):
- 4
- Justification:
- Default (DNEL calculator)
- AF for other interspecies differences:
- 2.5
- Justification:
- Default (DNEL calculator)
- AF for intraspecies differences:
- 10
- Justification:
- Default (DNEL calculator)
- AF for the quality of the whole database:
- 1
- Justification:
- Default (DNEL calculator)
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 substance is used as an intermediate and only in industrial settings in the UK. No exposure to the general population is envisage.
It should be noted that the susbtance is not used within the EU, the substance is imported and then directly exported.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.
Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
