What the Hex is with Chromium

1
What the Hex is with Chromium?

• OSHAs Hexavalent Chromium Standard
• Summary of Hazards
• Initial Exposure Determinations in Stainless
  Steel Making, Carbon Steel Making and Stainless
  Steel Fabricating Industries Welding/Torch
  Cutting

B. Quinn, CIH 1/23/07
Welder using Plasma Cutter
2
OSHA Hexavalent Chromium Standard

• General Industry - 1910.1026
• Shipyards - 1915.1026
• Construction - 1926.1126
• Most requirements are generally the same for all
  industries

3
Exceptions to the New Standard

• Does not impact application of some pesticides
  (EPA regulated)
• Does not impact exposures to Portland cement
• Does not impact situations in which the employer
  has objective data demonstrating that a material
  containing chromium or specific operation or
  activity cannot release Cr (VI) in concentrations
  at or above 0.5 µg/m3 as an 8 hour TWA
• Partial Exemption if exposure is less than 30
  days of the year

4
What is Hexavalent Chromium?

• Hex Chrome means chromium with a valence of
  positive six, in any form or chemical compound in
  which it occurs. This term includes Cr6 in all
  states of matter, in any solution or other
  mixture, even if it is encapsulated by another
  substance.
• Stainless steel does not contain hexavalent
  chromium. Zero state with Cr III on surface
• However, chrome is a raw material used in many of
  the specialty metals

5
What is Hexavalent Chromium?

• Hex chrome can be generated during certain hot
  work processes. In these instances, the chrome
  in the metal changes valance upon heating.
• The primary route of entry for hexavalent
  chromium (Cr6) compounds into the body when in a
  fume state would be inhalation.

6
Why Is Hex Chrome A Concern?

• POTENTIAL HEALTH EFFECTS
• Lung cancer
• Nasal septum ulcerations and perforations
• Asthma
• Skin ulcers
• Allergic and irritant contact dermatitis

7
Health Concerns
Permanent perforation of the nasal septum from
continuous exposure performing chrome plating of
small appliance parts
Chrome hole on finger. Can also occur on hands
or forearms, and on bottom surfaces of feet from
chrome salts permeating through boots or shoes.
8
Chromates have Varying Solubilities

• Highly soluble in water
• Sodium dichromate
• Chromic acid
• Slightly soluble in water
• Calcium chromate
• Strontium chromate
• Zinc chromate
• Insoluble in water
• Lead chromate
• Barium chromate

9
Carcinogenic Effects Lung Cancer

• Cells uptake Cr(VI)
• Faster for soluble forms of Cr(VI)
• Insoluble chromates concentrate
• Particles lt 10 µm contact target cells
• Cells react with Cr(VI) to form Cr(III) and toxic
  byproducts, Reactive Oxygen Species
• DNA is damaged
• Cell replication disturbed

10
Sources of Occupational Exposure
11
Major operations/job tasks resulting in potential
Cr(VI) exposure

• Chrome plating/Electroplating
• Welding on stainless steel or Cr(VI) painted
  surfaces
• Painting
• Aerospace
• Auto body repair
• Chromate pigmentand chemical production

Chrome Plating Bath
12
Major operations/job tasks resulting in potential
Cr(VI) exposure

• Chromium dye and catalyst production
• Glass manufacturing
• Plastic colorant production
• Construction
• Traffic painting
• Refractory brick restoration
• Paint removal from bridges

Bridgework
13
Stainless and Carbon Steel operations/job tasks
with potential Cr(VI) exposure
Melting Casting Continuous Teeming Baghouse To
rch Cutting/Oxygen Lancing Grinding Hot
Rolling Welding/Plasma Torch Cutting
14
Steel Process Flow
15
Steel Process Flow
16
OSHA Hexavalent Chromium Standard

• In 2006, OSHA passed a new regulation pertaining
  to Hexavalent Chromium.
• General Industry Standard 1910.1026
• There are 13 major provisions to the Standard
• The following is a summaryof these provisions

17
OSHA Hexavalent Chromium Standard

• Provision 1 -- Scope Who is Covered by the
  Standard?
• All occupational exposures to Cr6 compounds
  except
• Where employers have objective data demonstrating
  that a material containing chromium or a process
  involving chromium cannot release Cr6 in
  concentrations at or above 0.5 µg/m3 as an 8-hour
  time-weighted average (TWA) under any condition
  of use.
• Provision 2 Permissible Exposure Limits
• PEL 5 µg/m3 TWA
• AL 2.5 µg/m3 TWA (50 of the PEL)

18
OSHA Hexavalent Chromium Standard

• Provision 3 Exposure Determination
• Each employer who has a workplace or work
  operation covered by this Standard shall
  determine the 8-hour TWA exposure for each
  employee exposed to Hexavalent Chromium (Cr6).
• Two options for determining employee exposures
• Scheduled monitoring method
• Performance-oriented monitoring method
• If initial monitoring indicates exposures above
  the PEL or Action Level, future periodic
  monitoring is required
• Above the AL Monitor every 6 months
• Above the PEL Monitor every 3 months

19
OSHA Hexavalent Chromium Standard

• Provision 4 Regulated Areas
• Areas where exposures exceed or can be reasonably
  expected to exceed the PEL
• Must be demarcated from other areas
• Must limit access to employees who have a need to
  be there
• Performance wording of warning signs
• Provision 5 Methods of Compliance

• Engineering and work practice controls are the
  primary means of achieving exposures below the
  PEL.
• Use of respirators may be used to achieve the PEL
  during
• Periods necessary to install or implement
  feasible engineering and work practice
  controls Maintenance or repair operations where
  engineering and work practice controls are
  not feasible Operations where all feasible
  controls have been used and exposures are still
  above the PEL Operations where exposures do not
  exceed the PEL for 30 or more days per
  year Emergencies

20
OSHA Hexavalent Chromium Standard

• Provision 6 Respiratory Protection

• Shall be used in situations as described above
  and must comply with the requirements set forth
  29 CFR 1910.134. We will review these
  requirements in a later slide.

Provision 7 Protective Work Clothing
Equipment

• Must use where a hazard is present or is likely
  to be present from skin or eye contact with Cr6
• Must be provided and paid for by the employer
• Remove Cr6 contaminated clothing and equipment
  when work shift or task is completed
• Clean, store and label Cr6 contaminated clothing
  and equipment

21
OSHA Hexavalent Chromium Standard

• Provision 8 Hygiene Areas and Practices

Where protective clothing is required, must
provide change rooms and washing
facilitiesEmployees must wash their hands and
face at the end of a work shift and prior to
eating, drinking, smoking
Employer-provided eating
areas must be kept as free as practicable of
Cr6No eating, drinking, smoking etc. in
regulated areas
Provision 9 Housekeeping
All surfaces must be kept as free as practicable
of accumulations of Cr6 Use HEPA vacuums or
other methods that minimize exposure to Cr6
Use of compressed air prohibited unlessUsed in
conjunction with a ventilation system to capture
the dust cloud created by the compressed air,
or No alternative method is feasibleDispose of
Cr6 contaminated waste in labeled, impermeable
bags/containers
22
OSHA Hexavalent Chromium Standard

• Provision 10 Communication of Hazards

Training must be provided on the contents of the
Cr6 standard and the purpose and description of
the medical surveillance program required by the
standard Training must be conducted to inform
employees of the protective measures being
instituted to control exposures and means used to
communicate potential exposure areas.
Provision 11 Medical Surveillance
Which employees must be provided Medical
Surveillance? Exposed at or above the Action
Level (2.5 µg/m3) for 30 or more days per
year. Experiencing signs or symptoms of Cr 6
exposure Exposed in an emergency What is Medical
Surveillance? Provisions for conducting baseline
and periodic health assessments of exposed
employeesProvided by or under the supervision of
a physician or other licensed health care
professional (PLHCP)Provided at no cost to
employee and at a reasonable place and time
23
OSHA Hexavalent Chromium Standard

• Provision 12 Recordkeeping

Must maintain records of Air monitoring
data,Historical monitoring data,Objective
data,Medical surveillance information,
includingHealth Care Professionals written
opinions,Information provided to the Health Care
Professional
Provision 13 Effective Dates
New OSHA Standard Effective Date May 30,
2006 Key Compliance Dates All provisions
except engineering controls For employers with 20
or more employees Nov. 27, 2006 Engineering
Controls For all employers May 31, 2010
24
Sampling Analytical OSHA ID-215 Method

• 37 mm NaOH pre-treated quartz fiber filter
  preferred for chrome plating operations
• 37 mm PVC filter (5.0 micron pore size, can use
  0.8 u as well) can use PVC at chrome plating
  but must be post/preped by lab. These must be
  analyzed within 6 days or prepared upon receipt
  at lab
• PVC filters used for welding must be analyzed
  within 8 days Iron II interference
• Submit to AIHA accredited lab 24 Hr

25
Summary Exposure Determinations

• Stainless Steelmaking 6 Melt shops, 4 Casters,
  2 Teeming, 5 Hot Rolling Mills, 8 AP Lines, 7
  Slitters and Related Torch Cutting/Welding
  Operations and baghouses
• Approximately, 1000 data points personals and
  areas along with settled dust and surface wipes.
• Exposures generally under AL sometimes a few
  exceeded AL, restricted to older Melt shops,
  elevated areas Charging Cranes above PELs (2 to
  15 ug/m3), hand torch cutting and welding at AL
  or PEL.

26
Summary Exposure Determinations

• Carbon Steelmaking HSLA, Galvanizing Lines and
  Tin (Chrome) Lines 8 Melt shops, 10 Galvanizing
  Lines, 1-Tin Line, and associated welding/torch
  cutting stainless and baghouses
• Approximately, 500 data points, personals and
  area samples
• Exposures have been below AL. Several area
  samples near spray application areas at galvanize
  lines have exceeded AL or PEL

27
Hex Cr Sources Steel Industry
28
Summary Exposure Determinations

• Welding and/or Plasma Torch Cutting Stainless
  and Carbon Steelmaking locations-maintenance and
  process lines, fabrication/weld shops on
  stainless steel.
• Approximately, 100 data points, personals and
  area samples.
• Exposures vary widely (less than AL to 5X PEL,
  dependent on many variables)

29
Welding Operations

• Most welding operations join metals by heating
  the base and/or filler metal to temperatures at
  or above the melting point and vaporization
  temperature of the weld joint material.
• Stainless steels or other chromium-containing
  alloys represent the source of hexavalent
  chromium in welding operations.

30
Welding Operations

• Except for resistance and laser welding, a weld
  pool of liquid metal is formed at the welding
  arc. A portion of the metal vapor, including
  chromium vapor originating from the base metal,
  consumable electrode, surface coating, or surface
  contaminants instantaneously reacts with
  atmospheric oxygen and condenses into solid
  particles (known as fume) to form metal oxides,
  such as iron oxide, and chromium oxides.
  Metallic chromium when vaporized, may react with
  oxygen to form both trivalent chromium (Cr2O3)and
  hexavalent chromium (CrO3) oxide-containing fume.

31
Welding Operations

• Two General Types of Welding- Manual or Automatic
  
• Manual - welding gun and electrode holder are
  hand held during manual welding operations, the
  welders breathing zone is within an arms length
  of the arc .

32
Welding Operations

• Common types -Manual Welding -Presented in
  decreasing order of relative welding fume
  generation rate.
• Flux Core Arc Welding (FCAW) consists of a wire
  electrode with arc shielding provided by flux
  contained within the electrode. One FCAW process
  variation uses an inert gas fed through the
  welding gun to provide additional shielding of
  the arc.
• Shielded Metal Arc Welding (SMAW), most common
  type. A short electrode with a coating.
• Gas Metal Arc Welding (GMAW) also known as MIG,
  second most common type. A wire electrode with an
  inert gas (e.g. argon) which is fed through the
  welding gun to provide a shield against
  oxidation.
• Tungsten Inert Gas Welding (TIG) uses a
  non-melting tungsten electrode and in some cases
  a metal filler that the welder introduces into
  the arc. An externally-supplied inert gas (e.g.
  helium, argon) is fed through the welding gun to
  shield the arc.

33
Welding Operations

• Automatic welding processes - typically performed
  with the welding machine operator positioned at a
  greater distance from the welding arc. In
  addition, automatic welding processes can be
  partially enclosed or isolated from personnel in
  the welding area. Examples of automatic welding
  processes are
• Submerged arc welding (SAW) uses a blanket of
  granular flux that is fed into the weld zone
  ahead of the electrode, and a shielding gas is
  not required.
• Plasma welding is performed by a plasma welding
  torch with a non-melting electrode located within
  a copper nozzle that has a small opening at the
  tip. The plasma is actually a gas that is heated
  to an extremely high temperature. The plasma
  gases are normally argon, and the torch also uses
  a secondary gas to shield the molten weld puddle.
• Laser welding uses a high energy beam process and
  the energy density of the laser is achieved by
  concentration of light waves. The focal spot
  (thousands of an inch in diameter) is targeted on
  the weld joint surface.

34
Welding Operations
Submerged Arc Welding
Plasma Welding
Laser Welding
35
Welding Processes and Fume Generation Rates
(g/min)

• FCAW-CO2 gt1
• FCAW-Ar/CO2 0.6
• GMAW-Steady 0.5
• SMAW 0.4
• GMAW-Pulsed 0.2
• GTAW lt0.1
• SAW lt0.1

36
Welder Exposures (µg/m3)

• SMAW 0.1 - 150
• FCAW 0.1 - 38
• GMAW 0.1 - 13
• GTAW LDL- 5
• SAW LDL - 0.7
• Plasma cutting 0.1- 20
• Metal cleaning (Grinding) 0.1 - 610

37
Controlling Welding Hex Cr Exposures

• The Hierarchy of Controls - Hexavalent Cr
• 1 - Engineering
• 2 - Administrative
• 3 - Personal Protective Equipment

38
Controlling Welding Hex Cr Exposures

• Flexible exhaust duct positioned near the welding
  arc.

39
Controlling Welding Hex Cr Exposures

• Down-draft Welding Tables with Filtration
  Another method of extracting fumes at the source
  is right at the table.
• Advantages Ventilation requires no operator
  adjustment, and fume extraction occurs at any
  point on the table.
• Limitations Less effective on large parts and
  part configurations that may interfere with
  exhaust air flow.

40
Controlling Welding Hex Cr Exposures

• Side-draft hoods and booths Provides directional
  exhaust ventilation to draw welding fumes away
  from the welder. Also available with production
  aids such as a turntable that allows rotation of
  larger parts to position the welder away from
  welding fume.
• Advantages Provides local exhaust ventilation
  over a relative large work area. Can accommodate
  larger size parts.
• Limitations Less effective when welding parts
  with configurations that impede air flow. For
  some welds, part configuration may require the
  welder to be positioned between the source of
  welding fume and hood exhaust.

41
Controlling Welding Hex Cr Exposures

• Fume Extractor guns Capture welding fumes at the
  source through a ventilation intake nozzle
  located immediately adjacent to, or integrated
  around the welding gun shielding gas/welding wire
  nozzle. Used on GMAW and FCAW applications.
• Advantages Requires no operator positioning of
  the exhaust system. The fume extractor gun can
  provide exhaust ventilation in restricted areas
  not accessible by other exhaust ventilation
  systems.
• Limitations Fume extractor guns are typically
  heavier, have a larger grip circumference, and
  the gun nozzles are larger diameter than
  comparable GMAW and FCAW welding guns not
  equipped with fume extraction. Less effective
  fume collection during welding on angle and
  corner section than when welding on flat surfaces.

42
Welding Studies Summary (FEG)

• A welding shop study where grade 321 stainless
  steel was GMAW welded, use of FEGs achieved a
  hexavalent chromium reduction ranging from 26
  79 (20.2 µg/m3 reduced to 15 4.2 µg/m3).
• Source Kura, 1998.

43
Controlling Welding Hex Cr Exposures

• Additional Engineering Controls Process
  Modification
• Modify the composition of shielding gas

Replace SMAW with GMAW
Reduce Sodium and Potassium Content in SMAW
Welding Electrodes (Rods)
Replace Typical GMAW Welding Systems With
Pulse-Arc GMAW
44
Welding Studies Summary

• Hexavalent chromium in SMAW fume ranged between
  47 to 62 percent of the total chromium in the
  fume measured
• Hexavalent chromium in GMAW fume from stainless
  steel is approximately 4 percent of the total
  chromium in the fume measured.
• The large amount of hexavalent chromium found in
  most fumes created by SMAW welding of stainless
  steel has been shown to be associated with the
  sodium and potassium compounds in SMAW welding
  fluxes. It is almost certain that the hexavalent
  chromium is present in such fumes as chromates of
  these metals, Na2CrO4 and K2CrO4. It is possible
  that the stability of these compounds compared to
  most other metal chromates prevents or minimizes
  the processes leading to reduction of hexavalent
  chromium in GMAW fume. Sodium and potassium
  chromates are also stable at higher temperatures
  than most other chromates and this could explain
  the much faster formation of hexavalent chromium
  in SMAW fume than in GMAW fume.

45
Welding Studies Summary (Replace SMAW with GMAW)

• Welding research suggests that chromium-containing
  fume created by GMAW welding on stainless steel
  can continue to evolve chemically for several
  minutes. In some cases, the hexavalent chromium
  content in the fume appears to rise to a maximum
  approximately 20 seconds after formation of the
  fume and then partly decays to trivalent chromium
  again. Unlike GMAW fume, no changes in
  hexavalent chromium concentrations were found in
  SMAW welding fume, suggesting that not all
  welding fume is subject to aging.
• Limitations GMAW welding equipment is not as
  readily transported or moved as SMAW equipment.
  Unlike SMAW, GMAW equipment includes 1- a wire
  feeder unit, 2- a supply of inert shielding gas
  typically from a compressed gas cylinder and 3-
  a welding gun supply hose/cable that carries
  electric power, electrode wire, and inert
  shielding gas to the welding gun.
• Sources Gray, et. al., 1983 Karlsen, et al.,
  1992 Zatka, 1985

46
Welding Studies Summary (Modify the composition
of shielding gas)

• Shielding gases with high oxygen potentials, such
  as CO2, produce more fume than argon-based
  shielding gases.
• Although use of 100 percent carbon dioxide as a
  shielding gas for FCAW results in higher fume
  generation, it is still the most commonly used
  gas for FCAW welding, used in slightly more than
  50 percent of FCAW applications, due to low cost
  and easy availability.
• The second most popular shielding gas for FCAW
  consists of 75 argon and 25 carbon dioxide.
• Reducing the CO2 content of shielding gas used
  for FCAW can reduce the fume generation rate and
  potentially the exposure of workers.

47
Welding Studies Summary (Modify the composition
of shielding gas)

• Reductions in fume generation rates can be
  achieved with FCAW with stainless steel
  electrodes. The fume generation rate (FGR) for
  an E309LT electrode using 100 percent CO2
  shielding gas was measured to be approximately
  0.6 grams/minute (g/min). The same electrode
  welded using 75 argon-25 CO2 shielding gas
  resulted in a reduction of FGR to as low as 0.3
  g/min. Additional FGR measurements for E309LT and
  E316T electrodes using 95 argon-5 CO2
  shielding gas show that FGR could be as low as
  0.1 g/min.
• Limitations Present commercial FCAW electrodes
  for stainless steels are not formulated for 95
  argon-5 CO2 shielding gas. Formulation changes
  would be required to take advantage of the
  reduced FGR.
• Source Edison Welding Institute, 2003

48
Welding Studies Summary (Reduce Sodium and
Potassium Content in SMAW Welding Electrodes
(Rods))

• The presence of sodium and potassium in the flux
  or coating of SMAW stainless steel welding rods
  and FCAW welding wire results in the production
  of fume containing higher concentrations of
  hexavalent chromium. Hexavalent chromium is
  produced when welding flux components combine
  with atmospheric oxygen to form Na2CrO4 and
  K2CrO4.
• When the sodium and potassium content of the
  coating of E-308 welding rod was lowered from the
  range of 2 to 5 percent - typically found in SMAW
  welding electrodes - to less than 1 percent, the
  emission rate for total chromium was reduced by
  30 percent and for hexavalent chromium by 94
  percent. Reducing the amount of these elements in
  electrodes and fluxes will reduce the production
  of hexavalent chromium in the welding fume by
  reducing the ratio of hexavalent chromium to
  trivalent chromium.

49
Welding Studies Summary (Reduce Sodium and
Potassium Content in SMAW Welding Electrodes
(Rods))

• Welding equipment manufacturers presently offer
  welding rods that contain lower sodium and
  potassium.
• Limitations Low sodium and potassium welding
  electrodes are not commercially popular because
  they reportedly produce slag that is more
  difficult to remove and the arc characteristics
  create a weld bead with a ropy or wavy appearance
  compared to SMAW welding electrodes that
  contain typical amounts of sodium and potassium.
  Despite these cosmetic issues, there are no
  reported weld quality or performance problems
  associated with the low sodium or potassium
  welding rods on the market.

• Sources Hewitt and Hirst, 1993 Kimura et. al.,
  1979 R.K. Tandon, et al., 1986 and Palmer, 1987
  

50
Welding Studies Summary (Replace Typical GMAW
Welding Systems With Pulse-Arc GMAW)

• Advances in welding power source technology
  involving the use of pulsed welding current can
  reduce fume generation of GMAW compared to
  conventional procedures. For example, a
  significant reduction of welding fume emission,
  by up to 80 percent, is attainable using the
  pulsed arc process as compared to the short arc
  process. With the pulsed arc, the weld bead is
  transferred without short-circuiting, in much the
  same way as the spray arc. The pulsed arc welding
  process avoids increased fume emission due to
  explosive bead detachment as a short circuit
  occurs.
• The reduction in welding fume that can be
  achieved by using pulsed welding current is
  demonstrated by shipyard tests. Operator
  exposure to hexavalent chromium was measured for
  pulsed gas metal arc welding (GMAW-P) of HY80 and
  HY100 steels (which contain 0.5-1.5 chromium),
  stainless steel (CRES), and nickel alloys. These
  tests show the value of pulsed GMAW welding in
  reducing hexavalent chromium exposures. The
  overall average hexavalent chromium exposure was
  0.23 µg/m3 with a median of 0.15 µg/m3 for 8
  measurements when welding several base metals
  with nickel alloy 625 and 276 alloy electrodes.
  This represents a 75 reduction compared to the
  GMAW baseline value.
• Sources Stern, February 1985 and Edison
  Welding Institute, 2003.

51
Respiratory Protection OSHA 1910.134-APFs
 
52
Respiratory Protection OSHA 1910.134-APFs

• Notes1Employers may select respirators assigned
  for use in higher workplace concentrations of a
  hazardous substance for use at lower
  concentrations of that substance, or when
  required respirator use is independent of
  concentration.
• 2The assigned protection factors in Table 1 are
  only effective when the employer implements a
  continuing, effective respirator program as
  required by this section (29 CFR 1910.134),
  including training, fit testing, maintenance, and
  use requirements.
• 3This APF category includes filtering facepieces,
  and half masks with elastomeric facepieces.
• 4The employer must have evidence provided by the
  respirator manufacturer that testing of these
  respirators demonstrates performance at a level
  of protection of 1,000 or greater to receive an
  APF of 1,000. This level of performance can best
  be demonstrated by performing a WPF or SWPF study
  or equivalent testing. Absent such testing, all
  other PAPRs and SARs with helmets/hoods are to be
  treated as loose-fitting facepiece respirators,
  and receive an APF of 25.
• 5These APFs do not apply to respirators used
  solely for escape. For escape respirators used in
  association with specific substances covered by
  29 CFR 1910 subpart Z, employers must refer to
  the appropriate substance-specific standards in
  that subpart. Escape respirators for other IDLH
  atmospheres are specified by 29 CFR 1910.134
  (d)(2)(ii).

53
Respiratory Protection

• Any NIOSH approved filter
• P-100 (as shown) is best
• Can use up to 10X the PEL (50 ug/m3)

54
Respiratory Protection

• Full-Face Respirator
• Any NIOSH approved filter
• Can use up to 50X the PEL (250 ug/m3-for hex
  chromium)

55
Respiratory Protection

• Powered Respirator (PAPR)

• Used with full-face respirator
• High Efficiency (N,R or P-95) or HEPA (N,R or
  P-100) filter preferably P-100
• Can use up to 50X the PEL (unless mfr can attest
  to 1000x)

56
Respiratory Protection

• Welders Hood/PAPR Combination
• 25x PEL or 1000x PEL with written testament of
  Mfr. (125 ug/m3 or 5,000 ug/m3 for hexavalent
  chromium)

57
Respiratory Protection

• Air Line Respirators Supplied Air

• Constant- Flow
• Positive Pressure
• No filter required
• Can be used up to 25X or 1000X the PEL with Mfr.
  Written testament

58
Summary

• New Hexavalent Chromium Std.
• Affects several industries chromates-Painting,
  electroplating, welding stainless
• Stainless steel mfr. Limited exposure sources
  older melt shop-elevated areas
• Chromic acid areas and operations Carbon Steel
• Welding many variables time,type,controls,
  filler rods
• Local exhaust ventilation

59
References

• www.nsrp.org Navy and National Shipbuilding
  Research Program 1998 published report
• www.ewi.org/njc the Edison Welding Institute
  report contracted by NSRP and published in 2003
• www.osha.gov/SLTC/hexavalent chromium/index.html
  - hex chrome compliance assistance
• www.lni.wa.gov/safety training kit- ppt. Hex
  Cr