This document discusses occupational hygiene and measuring exposure to hazardous substances like sulphuric acid mist. It explains that a new workplace exposure limit has been set for the thoracic fraction of sulphuric acid mist. Two options for measuring exposure are discussed: 1) sampling the inhalable fraction, which would overestimate thoracic exposure but may still indicate if the limit is exceeded, and 2) developing a validated method for directly measuring the thoracic fraction, which would be expensive. Interpreting exposure measurement results and correcting for background also need consideration.

1. Mike Slater

2. This Slideshare version of the
presentation includes some
additional explanatory text not
included on the original slides

3. Recognition Evaluation Control

4. Recognition Evaluation Control
Occupational hygiene is about preventing ill
health at work

5. Recognition Evaluation Control
Measuring exposure to hazardous
substances can be an important part of that
process

7. A new Workplace Exposure Limit (WEL) has
recently been introduced for sulphuric acid mist

8. It’s the first limit to be specified as the thoracic
fraction

9. The “thoracic
fraction” includes
those particles that
can deposit in the
regions of the
respiratory system
coloured blue and
pink on this diagram
Image Source: http://www.skcinc.com

10. Criteria for selecting a suitable
method:

11. Criteria for selecting a suitable
method:
Specificity


12. Criteria for selecting a suitable
method:
Specificity

No interferences from other
compounds that may be present

13. Criteria for selecting a suitable
method:
Specificity

Sensitivity


14. Criteria for selecting a suitable
method:
Specificity

Sensitivity

preferably can detect
concentrations as low as 1/10th
of the WEL (i.e. 0.005mg/m3)

15. Criteria for selecting a suitable
method:
Specificity

Sensitivity

Thoracic fraction


16. Criteria for selecting a suitable
method:
Specificity

Sensitivity

Thoracic fraction

Personal sampling


17. BS ISO 21438-1: 2007
Workplace atmospheres – Determination of
inorganic acids by ion chromatography,
part 1: Non-volatile acids (sulphuric acid and
phosphoric acid)

18. BS ISO 21438-1: 2007
Workplace atmospheres – Determination of
inorganic acids by ion chromatography,
part 1: Non-volatile acids (sulphuric acid and
phosphoric acid)
The method commonly used in the UK

19. BS ISO 21438-1: 2007
Workplace atmospheres – Determination of
inorganic acids by ion chromatography,
part 1: Non-volatile acids (sulphuric acid and
phosphoric acid)
This collects the inhalable fraction

20. Source:www.tsi.com

21. Particulates
Inhalable Thoracic Respirable

22. Particulates
Inhalable Thoracic Respirable
Lets look at the methods used to collect
the different fractions

23. Particulates
Inhalable Thoracic Respirable

24. Inhalable Fraction
7 hole head IOM head Filter cassette
Operate at 2 litres/minute

25. I.O.M sampler
The common sampler used in the UK

26. BS ISO 21438-1: 2007
Workplace atmospheres – Determination of
inorganic acids by ion chromatography,
part 1: Non-volatile acids (sulphuric acid and
phosphoric acid)
Collects the inhalable
fraction

27. Particulates
Inhalable Thoracic Respirable

28. Respirable Fraction
The cyclone sampler
Source: http://www.skcinc.com

29. Particulates
Inhalable Thoracic Respirable

30. Thoracic Fraction

31. Thoracic Fraction
A universal method has not been
established

32. Thoracic Fraction
So let’s look at some possible options

33. Respirable - Thoracic Cyclones
This sampler is used
for oil mist in the USA
Source: www.bgiusa.com/ihi/hfrtc.htm

34. Parallel Particle Impactor
Size-selective Samplers for Thoracic or
Respirable Particulates
Source: http://www.skcinc.com/prod/225-380.asp

35. So what are the options for
sampling sulphuric acid mist?

36. Criteria for selecting a suitable
method:
Specificity

Sensitivity

Thoracic fraction

Personal sampling


38. Nyrstar method
Staplex Model
TFIA-2F high
volume sampler
with 4-inch
diameter filter

39. Nyrstar method
Not personal
sampling

40. Nyrstar method
Not thoracic
fraction

41. Nyrstar method
Specificity

Sensitivity

Thoracic fraction

Personal sampling


42. Source:www.tsi.com

43. Option 1
 Sample for inhalable fraction

44. BS ISO 21438-1: 2007
Specificity

Sensitivity

Thoracic fraction

Personal sampling


45. BS ISO 21438-1: 2007
Specificity

TheSensitivity with interferences can be
problems
overcome

Thoracic fraction

Personal sampling


46. Option 1
 Sample for inhalable fraction
This approach will overestimate the
thoracic fraction

47. Option 1
 Sample for inhalable fraction
But if results lower than 0.05 mg/m3,
then the thoracic concentration will be
well below the limit

48. Option 1
 Sample for inhalable fraction
If results substantially higher than
0.05 mg/m3, then it is likely that the
limit will be exceeded

49. Option 1
 Sample for inhalable fraction
But results will be difficult to interpret if
they are just above 0.05 mg/m3

50. Option 2
 Develop and validate a method for the
thoracic fraction of sulphuric acid mist

51. Option 2
 Develop and validate a method for the
thoracic fraction of sulphuric acid mist
Method development and validation
will be expensive

52. Option 2
 Develop and validate a method for the
thoracic fraction of sulphuric acid mist
I think it is unlikely that HSE will fund
this

53. Other important considerations
 Correcting for background sulphate
 Sampling strategy
 Interpreting results

54. mike@diamondenv.co.uk
www.diamondenv.co.uk
http://diamondenv.wordpress.com
www.slideshare.net/mikeslater
Twitter @diamondenv
Mike Slater

55. Mike Slater, Diamond Environmental Ltd. (mike@diamondenv.co.uk)
This presentation is distributed under the Creative Commons
Attribution-NonCommercial-ShareAlike
UK:International Licence