Hydrothermal synthesis product of calcium oxide, quartz and water

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

repeated dose toxicity: inhalation, other

Remarks:

historical human data

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Remarks:

Recommendation from the Scientific Committee on Occupational Exoposure Limits TRGS 900

Data source

Reference

Reference 1

Reference Type:

review article or handbook

Title:

Unnamed

Year:

2003

Report date:

2003

Reference 2

Reference Type:

other: Technische Regeln für Gefahrstoffe (TRGS) 900

Title:

Unnamed

Year:

2001

Materials and methods

Test guideline

Qualifier:

no guideline required

Principles of method if other than guideline:

Recommendation from the Scientific Committee on Occupational Exposure Limits for Silica, Crystalline (respirable dust)

GLP compliance:

no

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Silicic acid, calcium salt

EC Number:

215-710-8

EC Name:

Silicic acid, calcium salt

Cas Number:

1344-95-2

IUPAC Name:

Silicic acid, Calcium salt

Test material form:

solid

Results and discussion

Effect levels

1

Key result

Dose descriptor:

NOAEL

Effect level:

0.02 mg/m³ air

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: see 'Remark'

2

Key result

Dose descriptor:

other: dust limit

Effect level:

3 mg/m³ air

Based on:

other: alveoli fraction

Sex:

male/female

Basis for effect level:

other: alveoli fraction

3

Key result

Dose descriptor:

other: dust limit

Effect level:

4 mg/m³ air

Based on:

other: respirable fraction

Sex:

male/female

Basis for effect level:

other: alveoli fraction

Target system / organ toxicity

Key result

Critical effects observed:

no

Applicant's summary and conclusion

Conclusions:

Based on long-term human data for crystalline silica a NOAEL of <= 0.02 mg/m³ was derived.
General dust limits of 4 mg/m³ (respirable fraction) and 3 mg/m³ (alveoli fraction) were determined.

Executive summary:

In a review of the results of epidemiological studies of silicosis prevalence (WHO 1986) the threshold value suggested for the avoidance of silicosis is a time-weighted average concentration of respirable crystalline silica dust of 0.04 mg/m³ for an 8-hour shift, 40-hour week and 35-year working life.

From the results of studies reviewed by the MAK Commission, a NOAEL for the respirable crystalline silica dust concentration can be derived, at best in the range below 0.020 mg/m³. This concentration, which is in the range of the detection limit of the currently used analytical method with personal sampling, was obtained mathematically by extrapolation from higher concentrations for shorter exposure periods to a working lifetime of 45 years. Use of a mathematical model without a threshold value predicts that reduction of the concentration of respirable crystalline silica dust to 0.05 mg/m3, measured as the average concentration during 40 years, corresponding to a cumulative exposure level of 2 mg/m³ × years, could reduce the cumulative silicosis risk below that resulting from higher level exposures.

According to the "Ausschuss für Gefahrstoffe" general dust limits were determined: 4 mg/m³ (respirable fraction) and 3 mg/m³ (alveoli fraction).