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Physical & Chemical properties

Particle size distribution (Granulometry)

Administrative data

Endpoint:
particle size distribution (granulometry)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
8-9 March 2006
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with national standard methods

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2006
Report date:
2006

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
other: ISO 7708: 1995(E) HSE 2000 MDHS 14
Principles of method if other than guideline:
The test used in this study allows particles to become dissociated (and possibly airborne) without the concomitant milling and attrition caused by conventional techniques of aerosol generation. It can therefore be used to assess, realistically, the airborne hazard likely to be associated with a powder during its normal modes of handling.

Once the particles have been dissociated, they are classified on the basis of their settling velocity in a vertical elutriator. The settling velocity of an airborne particle is inversely proportional to its aerodynamic diameter and it is the latter which governs the inhalability and fate of the particle within the respiratory tract. A vertical elutriator classifies particles on a pass/no pass basis. If the settling velocity of the particle is greater than the velocity of air passing up the elutriator, then the particle will settle back into the bulk sample. As the settling velocity of the particles approaches the cut point of the elutriator, the particles will travel further up the elutriator and will eventually escape, once their settling velocity is lower than the elutriation velocity of the air.

By weighing the elutriator before and after an elutriation period, the proportion of sample having an aerodynamic equivalent diameter less than the cut point of the elutriator can be calculated. A series of such measurements made at a range of velocities will enable a cumulative plot of “apparent” aerodynamic diameter to be made, from which deductions about the particle size distribution of the test substance and the associated inhalation hazard can be made.

During the elutriation period, the bed of test substance is fluidised by shaking on an Analysette III sieve shaker set at an amplitude of 1-3mm. This agitation is especially important as the lower flow rates will not alone cause sufficient mixing to allow all available particles to be elutriated
within a reasonable measurement period. The measurement period per elutriation velocity is set at 30 minutes, which is adequate to provide relevant data whilst avoiding any significant attrition to the test substance.
GLP compliance:
yes
Type of method:
other: The aerodynamic particle size distribution assessed by air elutriation.
Type of particle tested:
primary particle
Type of distribution:
mass based distribution

Test material

Constituent 1
Test material form:
solid: particulate/powder
Details on test material:
Light pink tinted powder

Results and discussion

Remarks on result:
other: AED
Remarks:
3.42% of the test substance eluted at an AED of <115 µm
Particle size
Key result
Remarks on result:
other: 3.42% being less than or equivalent to 115 µm aerodynamic equivalent diameter (AED). Approximately 0.03 % of the substance is classified as respirable according to UK and ISO definitions (2006)

Any other information on results incl. tables

The results derived from the mean of the two measurements taken using the elutriator were as follows:

 

AED*
(µm)

Weight loss (%)
Sample 1       Sample 2

Mean weight
loss (%)

Mean cumulative
loss (%)

<15

0.03

0.03

0.03

0.03

<35

0.03

0.13

0.08

0.12

<50

0.29

0.10

0.20

0.31

<75

0.39

0.43

0.41

0.72

<115

3.07

2.33

2.70

3.42

 

* This represents the aerodynamic cut points of the various elutriator velocities employed.

 

The results show that a proportion (3.42%) of the test substance eluted at an AED of <115 µm which is considered sufficient to represent the AED of

<100 µm specified by the HSE 2000.

Particle Size Distribution: Not determined
-------------------------------------------------------------
Mass Median Diameter: Not determined

Applicant's summary and conclusion

Conclusions:
A proportion of the test substance was capable of becoming airborne, 3.42% being less than or equivalent to 115 µm aerodynamic equivalent diameter (AED). Approximately 0.03 % of the substance is classified as respirable according to current UK and ISO definitions. This test substance is of low respirability.