Determination of Clearance
Criteria Following Mercury
Decontamination Projects
PO-115
American Industrial Hygiene Conference and Exposition
May 13-16, 2006
Chicago, Illinois
David Regelbrugge, CIH, CSP
Gary N. Crawford, CIH
Brad Caddick
Win Williams
PH: 847-692-4700
E-Mail: [email protected]
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Background
• How do you go about clearing a
mercury clean-up site?
– Few established methods for
identification, decontamination and/or
clearance of remediated areas.
2
Background
• Spills & Releases
– Most often seen in educational facilities
and hospitals.
• Spills may be from years of abuse or a
single careless incident
– For example, laboratory use vs. a student
finding or bring mercury from home to school to
show to fellow students.
– Rare but occasionally seen in homes.
3
Exposure Values
• Occupational Exposure Values
– OSHA
• Ceiling limit of 100 µg/m3
– ACGIH®
• TLV® of 25 µg/m3
• Also carries a “Skin” notation
4
Exposure Values
• Environmental Values
– Values vary between agencies
• EPA Reference Concentration 0.3 µg/m3
• Agency for Toxic Substances and Disease
Registry (ATSDR)
– 0.2 µg/m3 minimal risk level
– 3 µg/m3 for Industrial/commercial clearance
» For an 8 hr day
– <1 µg/m3 for residential clearance
» For a 24 hr day
– Which value should be used?
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Exposure Values
• Environmental Values
– Illinois gas regulators spills
• Began in July of 2000
• Older gas regulators (installed prior to
1961) contained approximately 135 grams
(two teaspoons) of liquid mercury.
• Located inside homes
• Mercury was spilled during replacement
• Approximately 200,000 homes affected
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Exposure Values
• Illinois environmental values
– Illinois Department of Public Health
(IDPH), the ATSDR, EPA and other
local agencies agreed upon acceptable
environmental levels.
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Illinois Re-occupancy
Environmental Levels
Level Acceptable for
Re-occupancy
Indoor Air
Concentration
Residential
<1 µg/m3
Industrial-Commercial
3 µg/m3
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Exposure Values
• Since there had been a consensus
between the IDPH, ATSDR, EPA
and other agencies in the Illinois
case, we decided to used the
ATSDR industrial-commercial
clearance level of 3 µg/m3.
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Assessment Strategy
•
Use direct reading instrument to survey
areas and identify potential areas of
concern.
–
Two instruments available
•
Instrument “A”
–
•
Instrument “B”
–
–
Detection minimum detection level of 3 µg/m3
Detection minimum detection level of 0.002 µg/m3
Instrument “B” was used due to the
increased sensitivity.
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Assessment Strategy
• Any area with visible mercury or
measurements above the Illinois
industrial/commercial clearance
levels (3 µg/m3) was considered
contaminated.
– Contour map developed or highlighted
photograph used to identify where
contamination was found.
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Remediation Strategy
• All contaminated areas were cleaned
by a contractor with mercury
remediation experience.
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Case Study 1
Mercury Contamination in Laboratory
13
Case Studies
• Case 1:
Laboratory where mercury had been
used in experiments for years. Lab
was scheduled for a major
renovation. Lab officials wanted the
area checked for asbestos and
mercury prior to
demolition/renovation.
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Case Study 1
• Initial assessment:
– Mercury concentrations ranged from
0.3 µg/m3 to >260 µg/m3
– Highest concentrations near a fume
hood
– Elevated concentrations also observed
above asbestos floor tile located near
the fume hood.
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Case Study 1
• Asbestos and mercury remediation
was recommended
• Contractor with asbestos and
mercury abatement experience was
hired to perform the remediation.
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Case Study 1
• Removal techniques
– Containment with decontamination
chamber (DCU)
– Workers wore disposable clothing and
respirators equipped with
HEPA/mercury filters.
– Vacuums and negative air machine
equipped with HEPA/mercury filters.
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Case Study 1
• Remediation techniques
– Asbestos materials removed first
• Increase in airborne mercury (Hg) vapors
seen when tile was removed
– Possible contamination under the tile?
– Following the asbestos removal
• Hg Sorb®, a mercury absorbent was used
on floor and other contaminated areas. This
was followed by a through cleaning of the
areas with Red Devil TSP/90®
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Case Study 1
• Air samples collected during
remediation
– Samples for both asbestos and mercury
collected during removal.
– Asbestos samples collected in
accordance with NIOSH 7400
– Mercury concentrations measured with
the direct reading instrument
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Case Study 1
• Multiple cleanings were conducted
– Cleaning process repeated for mercury
until area measurements indicated that
airborne mercury concentrations were
below 3 µg/m3 (ATSDR commercial
level)
• Cleanings performed 6 times over four
days
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Case Study 1
• Waste
– All asbestos waste double bagged
– All waste bags tested for mercury
contamination prior to disposal with the
direct reading instrument
• Waste > 1 µg/m3 (the residential clearance
criteria) considered potentially
contaminated and TCLP analysis
performed.
• If TCLP analysis indicated levels > 0.2
mg/L (EPA limit) the material was disposed
of as mercury waste.
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Case Study 1
• Waste (Continued)
– Any elemental mercury or known
mercury contaminated wastes were
placed into plastic drums or buckets.
– This waste was sent to a licensed metal
disposal/recycling facility.
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Case Study 1
• Final mercury air samples (continued)
– When direct reading instrument indicated that
mercury concentrations in the remediated area
were below 3 ug/m3 final air samples were
collected.
– Final air sampling methodology
• Five (5) samples collected throughout the lab
• NIOSH Method 6005 on SKC® Hydrar® sorbent
tubes
• seven to eight hours sampling duration
• Ambient temperature kept above 75oF during
collection
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Case Study 1
• Final mercury air samples (continued)
– Area was released when air samples
indicated the mercury concentrations
were at or below the ATSDR
industrial/commercial level of 3 µg/m3.
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Case Study 2
Mercury Contaminated Science Hall
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Case Study 2
• Case 2:
Three story college science hall
scheduled for sale and possible
demolition. Mercury use in building
was unknown but suspected. Limited
visible mercury observed in a couple
of areas.
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Case Study 2
• Mercury survey completed with the
direct reading instrument
• Same criteria used as in Case 1
• Isolated areas of mercury
contamination identified.
• Highlighted digital photographs used
to indicate contaminated areas.
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Case Study 2
Highlighted digital photographs used
to identify contaminated areas
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Case Study 2
• Mercury remediation of contaminated
areas recommended.
• Remediation performed, similar to
that used in Case 1.
– Regulated areas were used instead of
full containment.
• Limiting access to contaminated areas
• Full PPE for remediation crew.
• Disposable foot coverings used to prevent
potential tracking of mercury.
29
Case Study 2
• Direct reading instrument used to evaluate
remediation progress.
• Findings during remediation
– Visible mercury found underneath cabinets
and ceramic tiles near cabinets.
– Mercury detected in some of the drain pipes.
• Horizontal pipes removed
• Vertical pipes flushed with mercury surfactant
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Case Study 2
• Main catch basin for the building was
tested for mercury.
– Water & sludge tested
• Water results compared Local Sanitary
Districts discharge limits for mercury
• Sludge sent for TCLP analysis.
– Water and sludge were contaminated.
– Test performed prior to pipe cleaning.
31
Case Study 2
• On-site sewer system tested
– Same environmental criteria applied to
manholes as the catch basin.
– Mixed results
• Sludge contaminated in three of the four
manholes tested.
• Water in most manholes was not
contaminated.
32
Case Study 2
• On-site sewer system cleaned
– Cleaning performed by a licensed
hazardous waste/remediation
• Sewer vacuum/cleaning truck utilized.
• All sludge & water removed
– Direct reading instrument was used to
evaluate sewer cleaning
• Considered clean when measurements
below the ATSDR level of 3 µg/m3.
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Case Study 2
Visible mercury found underneath baseboard & cabinet
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Case Study 2
Bottom of cabinet and floor tile removed to access
mercury contamination.
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Case Study 2
Catch basin being cleaned
36
Case Study 2
• Final air samples (continued)
– When direct reading instrument indicated that
mercury concentrations were below 3 µg/m3
final air samples were collected.
– Final air sampling methodology
• Eight (8) samples collected on each floor of the
building.
• NIOSH Method 6005 on SKC® Hydrar® sorbent
tubes.
• Seven to eight hour sample duration.
• Ambient temperature kept above 75oF during
collection
37
Case Study 2
• Final air samples (continued)
– Area was released when air samples
indicated the mercury levels were at or
below the ATSDR industrial/commercial
clearance level of 3 µg/m3.
38
Lessons Learned
1. Instrument “B” was an excellent instrument
to use for the initial inspection, monitoring of
remediation and for use prior to final air
sampling.
2. Mercury contamination can be worse than it
originally appears.
3. The ATSDR’s recommended
industrial/commercial clearance level of 3
ug/m3 was achievable.
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Speaker Contact Information:
David C. Regelbrugge, CIH, CSP
Director, Environmental Health & Safety
Boelter & Yates, Inc.
847/685-9276
[email protected]
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