Lime (chemical), hydraulic

Particle size distribution (Granulometry)

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

particle size distribution (granulometry)

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods

Qualifier:

according to guideline

Guideline:

other: DIN 55992-1:2006 (Determination of a parameter for the dust formation of pigments and extenders – Part 1: Rotation method)

Deviations:

yes

Remarks:

Refer to principles of method section below

Principles of method if other than guideline:

The Heubach dust meter is modified in a way that a seven stage cascade impactor is connected to the system. This involves an additional air fed of 20 L/min via the coarse dust separator needed to supply the cascade impactor with 40 L/min air current as specified in the manufacturer’s specifications.
The calculation report: Grewe, T (2010)
The Multiple-Path Particle Dosimetry Model (MPPD, v2.0; CIIT, 2006) was used to predict this fractional deposition behaviour for workers.
The model algorithms calculate the deposition (and clearance) of mono-disperse and polydisperse aerosols in the respiratory tract for particles ranging from ultra-fine (0.01 microns) to coarse (20 microns) sizes. Within each airway, deposition is calculated using theoretically derived efficiencies for deposition by diffusion, sedimentation and impaction within the airway or airway bifurcation. Filtration of aerosols by the head is determined using empirical efficiency functions.

GLP compliance:

no

Type of method:

other: refer to principles of method above

Type of distribution:

volumetric distribution

Remarks on result:

other: refer to any other information on results below

Dustiness (airborne fraction): total: 69.11 mg/g.

In the original study report by DMT, a calculation of the mass median diameter was not conducted. Since the deposited fractions were provided for each of the cascade impactor stages, it was possible to fit a bimodal lognormal distribution to the data by a standard non-linear regression procedure. As a result, the MMAD and GSD are calculable and reported (p1: 54.0 %, MMAD1 = 6.68 µm, GSD1 = 1.97, p2: 46 %, MMAD2 = 32.21 µm, GSD2 = 1.10). As the cascade impactor already takes aerodynamic characteristics of the particles into account, the reported mass median diameter can be interpreted as the mass median aerodynamic diameter.

This figure and the corresponding GSD were used as distribution parameters for the MPPD model enabling an estimation of deposited dust fractions in the human respiratory tract: These fractions were estimated as follows:

Head (ET): 63.9 %

Tracheobronchial (TB): 0.9 %

Pulmonary (PU): 2.3 %

Conclusions:

Total Dustiness (airborne fraction): 69.11 mg/g (experimental result, DMT Report).

Mass median aerodynamic diamaters (bi-modal distribution) of airborne fraction: MMAD1 = 6.68 µm (54.0 %) , MMAD2 = 32.21 µm (46 %) (distribution fitted to cascade impactor data, percentage in parentheses indicates weighting factor).

Geometric standard deviation of MMAD: GSD1 = 1.97 µm, GSD 2 = 1.10 µm

Fractional deposition in human respiratory tract (MPPD model, based on calculated MMAD):
Head (ET): 63.9 %
Tracheobronchial (TB): 0.9 %
Pulmonary (PU): 2.3 %

Reference 2

Endpoint:

particle size distribution (granulometry)

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2010-03-05 to 2010-05-21

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

OECD Guideline 110 (Particle Size Distribution / Fibre Length and Diameter Distributions)

Version / remarks:

1981

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2009-11-26

Type of distribution:

volumetric distribution

Percentile:

D50

Remarks on result:

not determinable

Too few particles were of a size less than 10.0 µm to allow accurate assessment of the mass median aerodynamic diameter.

Sampling for the cascade impactor determinations was performed by rolling the test material container for approximately 10 minutes then sampled from the top, middle and bottom.

The inhalable fraction is defined as the mass fraction of particles which can be inhaled by nose or mouth, the thoracic fraction is defined as the mass fraction of particles that passes the larynx and the respirable fraction is defined as the mass fraction of particles that reaches the alveoli.

Particle size data acquired for the test material is as follows:

- Proportion of test material having an inhalable particle size < 100 µm: 96.6 % (sieve method)

- Proportion of test material having a thoracic particle size < 10.0 µm: 0.20 % (cascade impactor)

- Proportion of test material having a respirable particle size < 5.5 µm: 5 X 10^-2% (cascade impactor)

Conclusions:

Particle size data acquired for the test material is as follows:
- Proportion of test material having an inhalable particle size < 100 µm: 96.6 % (sieve method)
- Proportion of test material having a thoracic particle size < 10.0 µm: 0.20 % (cascade impactor)
- Proportion of test material having a respirable particle size < 5.5 µm: 5 X 10^-2% (cascade impactor)

Description of key information

Total Dustiness (airborne fraction): 69.11 mg/g (experimental result, DMT Report).

Mass median aerodynamic diamaters (bimodal distribution) of airborne fraction: MMAD1 = 6.68 µm (54.0 %) , MMAD2 = 32.21 µm (46 %) (distribution fitted to cascade impactor data, percentage in parentheses indicates weighting factor).

Geometric standard deviation: GSD1 = 1.97 µm, GSD 2 = 1.10 µm

Fractional deposition in human respiratory tract (MPPD model, based on the MMAD):

Head (ET): 63.9  %; Tracheobronchial (TB): 0.9 %; Pulmonary (PU): 2.3 %

Additional information

For the evaluation of this endpoint, data from a study (Parr, 2010; Grewe, 2010) that was conducted according to national standard (DIN 55992 -1:2006, modified Heubach method) were used as key information supported by data from a guideline compliant study (OECD 110, O'Connor and Wooley, 2010).

The key study was selected based on the fact that the study considers the airborne fraction of lime (chemical) hydraulic, which is exposure-related and relevant for workplace conditions. In the other study, used as supportive information, the airborne fraction of calcium dihydroxide was not determined, but the total of the substance fed in a cascade impactor. This is not exposure-related and not relevant for workplace conditions.