Registration Dossier

Toxicological information

Health surveillance data

Currently viewing:

Administrative data

health surveillance data
Type of information:
other: human data
Adequacy of study:
supporting study
Study period:
no data available
other: high
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Well-documented study on single and short-term exposure of humans to CaO. Calcium oxide is converted into calcium hydroxide in contact with water, i.e. under physiological conditions. Therefore, calcium hydroxide is intrinsically covered by the results of this study by read-across (point 1.5 of Annex XI of Regulation (EC) No.1907/2006). This is also taken into account by the SCOEL recommendation, to which the current study makes a signficant contribution.
Reason / purpose for cross-reference:
reference to same study

Data source

Reference Type:
Sensory and associated reactions to mineral dusts: Sodium borate, calcium oxide, and calcium sulfate
Cain, W.S.; et al.
Bibliographic source:
J. Occ. Environ. Hygiene, 1: 222-236

Materials and methods

Study type:
biological effect monitoring
Endpoint addressed:
acute toxicity: inhalation
respiratory irritation
Test guideline
no guideline available
Principles of method if other than guideline:
Controlled study of early sensory nasal irritation response.
GLP compliance:

Test material

Constituent 1
Reference substance name:
Calcium oxide
EC Number:
EC Name:
Calcium oxide
Cas Number:
Details on test material:
- Name of test material (as cited in study report): Calcium oxide dust (MMAD = 6.53 ± 0.76, GSD = 2.6 ± 0.00)
No further details are given.


Type of population:
Ethical approval:
confirmed and informed consent free of coercion received
Details on study design:
12 male healthy volunteers (age 18-35 years) exercised against a light load while they breathed air in a dome fed with controlled dust levels of CaO of 1, 2 or 5 mg/m³ for 20 min. The parameters studied included nasal resistance, nasal secretion, minute ventilation, heart rate, blood oxygenation, mucociliary transport time, and chemesthetic magnitude for eyes, nose, and throat. Chemesthetic magnitude was calibrated against pungency of CO2. Subjects registered time-dependent “feel” from exposures principally in the nose, secondarily in the throat, and hardly in the eyes. Each subject served as his own control. The CaO was mixed with hydrated CaSO4 at a ratio of 10 % (w/w). The MMAD and GSD were as follows: CaO: 6.53 ± 2.6 µm, CaSO4: 8.24±2.43 µm.

Results and discussion

Feelings were maximal in the nose, slightly lower in the throat and much lower in the eyes. The blank exposure (0 mg/m³) corresponded to about 7 % CO2 in the nose and the throat. The CaO exposures caused a steady increase in sensory irritation during the 20 min period and no steady state level was reached. In the nose, 1 and 2 mg/m³ gave rise to an equivalent effect at the end of the exposure, which corresponded to the irritation effect of about 15 % CO2. The 5 mg/m³ level had an effect equivalent to 20 % CO2. These values were significantly above the background. No significant effect occurred in nasal airway resistance, nasal secretion, or mucociliary clearance, determined by the saccharin test.

Applicant's summary and conclusion

Overall, the nose was identified as the target organ in this study. Volunteers experienced some sensory irritation and “feel” at levels of 5 mg/m³ and 1-2 mg/m³, respectively.
This study was used by SCOEL for establishing OELs for lime dust. SCOEL derived a STEL of 4 mg/m³ respirable dust to prevent sensory irritation.