1. ADEQUACY OF EXISTING AEROSOL SAMPLERS FOR MONITORING NORM EXPOSURES European ALARA Network 9th Workshop on Occupational Exposure to Natural Radiation Augsburg, 20th October 2005
Olivier Witschger
Aerosol Metrology Laboratory
INRS – Lorraine Centre

2. Background
November 1999 : 3rd Workshop of the European ALARA Network on “Managing Internal Exposures”.
“…there is a need to pursue efforts to improve the quality and accuracy of internal dose monitoring techniques (particularly personal air sampler) to fit with the specifications needed for analytical task dosimetry. The meeting recommends to the Commission and regulatory bodies, that they support research in that area.”
Within SMOPIE, the objective of the WP#4 was to study the potentially useful monitoring methods and tools relevant to optimisation of predictable occupational internal exposure under different work place conditions.

3. Aerosol sampling in the industrial hygiene context (1/2)
Aerosols are major sources of hazards in lots of occupational environments.
“Aerosol exposure” via inhalation is of great interest for many years…
To assess realistically and in a manner relevant to health the risk of aerosol exposure, there are five primary ingredients to consider:
Sampling criteria
Instrumentation
Analytical instrumentation
Sampling strategy
Limit value

4. Aerosol sampling in the industrial hygiene context (2/2)
The accurate measurement of aerosol exposure via inhalation requires sampling devices that match particle deposition to the relevant areas of the respiratory system.
Standards have been developed describing representative penetration of aerosol particles through the respiratory system.
These standards provide a basis for estimating the aerosol concentration potentially available to cause harm and underlie many industrial hygiene aerosol sampling methods.

5. Aerosol sampling in the radiological protection context (1/5)
Sampling in the radioprotection context differs from the industrial hygiene context for two reasons:
The targeted information is the effective dose (Sv)
The ICRP 66 Human Respiratory Tract Model (HRTM) already includes inhalation of particles in the respiratory tract.
Dose coefficient (Sv/Bq) should be applied to the “total” aerosol concentration
All measurements performed with commercially available aerosol samplers should be corrected for any deviation to the 100% sampling efficiency

6. Aerosol sampling in the radiological protection context (2/5)
To assess the “ambient” activity concentration or “true” exposure, correction should be made according to:
There is no unique factor: it depends on the aerosol (AMAD, GSD) and the sampling performance of the sampler.
(Bq/m3)
(Bq)

7. Aerosol sampling in the radiological protection context (3/5)
To assess the true effective dose (Sv), the situation is more complex…
(Sv)

8. Aerosol sampling in the radiological protection context (4/5)
The bias between the estimated dose and the true effective dose is given by:
To illustrate, situation #4 (AMAD and GSD are not known ) leads to:
In this theoretical example, the sampler that minimise the bias in the estimation of the dose is the thoracic sampler.

9. Aerosol samplers in the radiological protection context (5/5)
Using the generic method, a number of different situations have been evaluated for NORMs (radionuclides, lung absorption rates). See final report, annex 3, appendix 3.
Altogether from the calculations it appears that the bias is minimum when:
A thoracic sampler is used for NORM with lung absorption type S and M
An inhalable sampler is used for NORM with lung absorption type F
When ambient aerosol characteristics are not known, default values of 5 m (AMAD) and 2.5 (GSD) are used.
These above conclusions are valid whatever the particle size distribution of the ambient aerosol is (AMAD, GSD).

10. Aerosol samplers for measuring in the workplaces
The accuracy and relevance of aerosol samples taken within the workplace predominantly rely on selection of an appropriate aerosol sampler. However, filter selection, pump selection and use, sampling strategy also play a role in determining the accuracy and suitability of samples.
In the first place of sampling strategy, there is the question of area vs. personal sampling.

11. Aerosol samplers for measuring in the workplaces
Inhalable Personal Samplers
The filter cassettes (1 or 2 L/min)
Poor performances and exhibits specific problems (losses, uniformity of the deposit, difficult to be airtight etc.)
The IOM Inhalable Sampler (2 L/min)
Over-sampling and not adequate for radioactive analysis A B C

12. Aerosol samplers for measuring in the workplaces
Inhalable Personal Samplers
The Button Aerosol Sampler (4 L/min)
Recently developed, no losses or over-sampling, low sensitivity of incoming wind direction
The future… A B C

13. Aerosol samplers for measuring in the workplaces
Static samplers and aerosol spectrometers (static and personal)

14. Conclusion
The purpose of aerosol sampling in the the industrial hygiene context and in the radiological protection context is not the same.
A generic method has been proposed to facilitate the identification of the appropriate aerosol sampling technique in the radiological protection context.
For dose assessment of many NORM industries (compounds characterised by a slow or moderate absorption) a thoracic-type personal samplers is preferable.
When the particle size distribution of the ambient aerosol is not know (for sampling efficiency correction and dose coefficient), default values of 5 m (AMAD) and 2.5 (GSD) could be used.

15. Conclusion
Existing aerosol samplers have been (and continue to be) developed and tested for industrial hygiene purposes, means according to the inhalable, thoracic or respirable sampling criteria).
Research and development should be encouraged to:
Thoracic personal sampler showing good performances (efficiency, low sensitivity to wind, sample handling etc.)… and being inexpensive.
Increase flow-rate (pumps, sampler geometry)

16. ADEQUACY OF EXISTING AEROSOL SAMPLERS FOR MONITORING NORM EXPOSURES European ALARA Network 9th Workshop on Occupational Exposure to Natural Radiation Augsburg, 20th October 2005
Olivier Witschger
Aerosol Metrology Laboratory
INRS – Lorraine Centre