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Toxicological information

Repeated dose toxicity: inhalation

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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

Referenceopen allclose all

Reference Type:
review article or handbook
Title:
Unnamed
Year:
2003
Report Date:
2003
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

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid

Results and discussion

Effect levels

open allclose all
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'
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
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).