Key Elements for Stainless Steels

1
Key Elements for Stainless Steels

• Chromium
• Hexavalent cpds. Carcinogenic to humans
• Trivalent cpds. Unclassifiable as to
  carcinogenicity to humans
• Nickel
• Insoluble cpds. Carcinogenic to humans
• Manganese Neurological effects on humans
• Explore occupational exposure limits for
• manganese compounds
• as these are topical components of welding fume

2
Manganese Inorganic Compounds Exposure Limit

• Comparison of three derived limits from
• ACGIH TLV proposal 2002
• UK HSE WEL 2001
• IEH/IOM OEL proposal 2004
• (Criteria document for International Manganese
  Institute)

3
Definitions ACGIH Threshold Limit Value - TLV

• Health-based
• Conditions under which it is believed that
  nearly all workers may be repeatedly exposed day
  after day without adverse health effects

4
Definitions HSE Workplace Exposure Limit - WEL

• Maximum concentration of an airborne substance,
  averaged over a reference period, to which
  employees may be exposed by inhalation
• Coupled with 8 Principles of Good Practice
• Has regard to practicability and economics

5
IEH/IOM Occupational Exposure Limit OEL

• Prepared according to EU guidelines
• Health-based
• Based on criteria document for EU SCOEL

6
Review References

• ACGIH 57 references, more than 20 not cited in
  IEH/IOM
• HSE 27 references, 15 not cited in ACGIH
• IEH/IOM Approx. 575 references

7
Welding cited?

• ACGIH No
• HSE Yes, including
• IEH/IOM consumables manufacture

8
Manganese Critical Factors Cited

• Subclinical effects on central nervous system
• Disturbance of motor function, loss of fine
  control of intentional movements
• Adverse effects on fertility of male workers
  (ACGIH only)

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Common Factors for Specifying OEL

• Definition of
• LOAEL Lowest Observed Adverse Effect Level
• NOAEL - No Observed Adverse Effect Level

10
Key Studies
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Conclusion - ACGIH

• Roels LOAEL 0.035 mg/m3 resp.
• Lucchini LOAEL 0.097 mg/m3 inhal.
• Assume respirable fraction Inhalable/2.6
• Therefore LOAEL 0.037 mg/m3 resp.
• Recommended TLV 0.03 mg/m3 resp.

12
Conclusion - HSE

• Motor effects reported at
• 0.251.6 mg/m3 Mn
• Not possible to define LOAEL from
  exposure-response data
• Health benefit value optimum (127M)
  achievable protection at 0.5 mg/m3 limit
• Approved WEL 0.5 mg/m3

13
Conclusion IEH/IOM

• Systemic effects come from respirable fraction
• Supplementary inhalable limit required for
  possible but unproven gastrointestinal effects
• Key studies allow NOAEL to be estimated
• Recommended OEL 0.1 mg/m3 resp.
• (Supplementary limit 0.5 mg/m3 inhal.)

14
Equivalent Exposure Limits

• Inhalable exposure limits based on
• Inhalable/Respirable 2.5 e.g. in MnO
  processing
• ACGIH 0.075 mg/m3
• HSE 0.5
• IEH/IOM 0.25
• Ratio 1 3.3 6.7

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Exposure Limits - Welding

• (all fume respirable)
• ACGIH 0.03 mg/m3.
• HSE 0.5
• IEH/IOM 0.1
• Ratio 1 3.3 16.7

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Current Exposure Limits
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Calculating Total Fume Limit

• For substance A
• Fume Limit 100 x OEL(A)
• Concentration(A)

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Total Fume Limits - MMA

• For fume containing 5 CrVI, 5 Mn, 1Ni
• UK 1 mg/m3
• Netherlands 0.5 mg/m3
• (Cr key component)

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Total Fume Limits - MIG

• For fume containing 16 Cr, 12 Mn, 8Ni
• UK 3.3 mg/m3
• Sweden 1.25 mg/m3
• (Key component Cr for UK, Ni for Sweden)

20
Proposed Limits
21
Proposed Limits - Total Fume Limit

• For fume containing 5 CrVI, 5 Mn, 1Ni

22
Exposures in Practice

• 20 Duty cycle
• Welders head out of plume LEV for
• Total fume lt0.1 mg/m3
• (Carter)
• Shipyard exposures with or without LEV
• CrVI 0.005 mg/m3
• (Castner)

23
Exposure Limit Variation

• Some reasons
• Definition and legal status differ between
  countries
• Revision periods vary e.g. OSHA PEL for Mn

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Risk and OELs

• Further reasons for variation
• Definition of OEL requires
• Risk assessment - Scientific (?)
• Risk management Value judgement

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Indicative Occupational Exposure Limit

• Where an IOELV is established at Community
  level, Member States shall establish a national
  OEL, taking into account the Community limit, in
  accordance with national legislation and
  practice
• Directive 98/24/EC

26
Practical Guidance

• Few employers measure exposure
• Netherlands specifies practical requirements for
  compliance with regulations
• UK publishing guidance sheets based on good
  practice principles

27
Respiratory Protection

• Filter helmet or Air-fed helmet

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Conclusions

• Need for coordination of exposure limits
• Practicability must be taken into account
• Compliance has to be supported by guidance
• All welders need protection!