Extending the Validity of Sampling for Mercury at Low Levels by Modifying NIOSH Method 6009, Cold Vapor
Atomic AbsorptionVince Daliessio, CIH, Industrial
Hygiene Project ManagerScott Van Etten, National Director of
Industrial HygieneEMSL Analytical, Westmont NJ
The Problem
• Recently mercury-contaminated buildings have been recycled for residential use, without proper assessment or remediation
• NIOSH 6009 cannot see Mercury to appropriate clearance levels unmodified
Unique Properties
• Symbol Hg (hydrargyrum)• Has a significant vapor pressure
(0.0012 mm Hg)• Equilibrium concentration at STP
approximately 18mg/m3
Implications
• Density-flows to inaccessible areas• Liquid absorbed into porous
building materials• Amalgamates with other metals• Re-vaporizes slowly over time to
cause significant air concentrations
Why Is Mercury Bad?• Particularly toxic to developing brain,
nervous system, respiratory system, kidneys, teeth, gums, skin
Published Air Limits
• OSHA - PEL- 100 ug/m3• ACGIH - TLV- 25 ug/m3• ATSDR -(Cleanup)- 0.5 ug/m3• EPA - Rfc - 0.3 ug/m3• ATSDR - MRL - 0.1 ug/m3
Air Sampling by NIOSH 6009
• Particulates, vapor, both• MCEF (part.) Carulite (vapor)• 0.2 Liters per minute for 100
minutes• Current RL by CV-AAS is 0.05 ug
(0.5ug/m3 at 100L)
But the method falls short!• Air volume to hit the ACGIH Cleanup Level
(0.5ug/m3);0.05ug/0.0005mg/m3 = 100L
• Air volume to hit the EPA Reference Concentration (RfC - 0.3 ug/m3);
0.05ug/0.0003mg/m3 = 166L• Air volume to see the ACGIH Minimal Risk
Level (MRL - 0.1ug/m3);0.05ug/0.0001mg/m3 = 500L
Possible alternatives
• Rathje and Marcero(1976) - higher sorbent volume, higher flowrates and volumes than NIOSH 6009– Regulatory agencies often require agency
methods• EPA Method
– Gold-coated media, cost is significant• ICP-MS promises much lower detection
limits– Newer technology, methods are lacking, cost
Near-term solution
• Validate NIOSH 6009 for higher volumes– Spike tubes in the concentration range of
interest– Draw multiples of the method volume through
the tubes– Compare mass recoveries and reported
concentrations– Use these to support sampling at 2x-5x
method volume
Spiking Tubes
• Spiked with different volumes of saturated aerosol solution (18 mg/m3);– 3000 ul = 0.0540 ug– 5000 ul = 0.0900 ug– 8000 ul = 0.1440 ug
Results
• Spike masses reported were higher than expected– Lab temperature was higher than STP;
• 28C vs 25C
• Corrected spike masses were in good agreement
• Selected 8000ul spike (0.26ug Hg) for sample volume study
0.0000
0.0500
0.1000
0.1500
0.2000
0.2500
0.3000M
ass
ug
3000 3000 5000 5000 8000 8000 ReportLimit
Spike Volume ul
Spiking Study - Theoretical vs. Reported Mass
Theoretical MassReported Mass
Results - 1X method volume
• Good agreement with spiking study• Consistent recovery across multiple
samples– 0.17-0.23 ug
• Consistent air concentrations– 1.69 - 2.35 ug/m3
0.0000
0.0500
0.1000
0.1500
0.2000
0.2500
Rep
orte
d M
ass
ug1X Method Volume Reported Mass
HG0009HG0009AHG0010HG0010AHG0011HG0011AHG0012HG0012AHG0013HG0013AReport Limit
0.00
0.50
1.00
1.50
2.00
2.50
Air
Con
cent
ratio
n ug
/m3
1X Method Volume Reported Air Concentration
HG0009HG0009AHG0010HG0010AHG0011HG0011AHG0012HG0012AHG0013HG0013AReport Limit
Results - 2X method volume
• Fair agreement with spiking study• Somewhat consistent recovery across
multiple samples– 0.15-0.22 ug
• Somewhat consistent air concentrations– 0.69 - 1.67 ug/m3– 2 samples less than 200L
0.0000
0.0500
0.1000
0.1500
0.2000
0.2500
Rep
orte
d M
ass
ug2X Method Volume Reported Mass
HG0014HG0014AHG0015HG0015AHG0016HG0016AHG0017HG0017AHG0018HG0018AReport Limit
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
Air
Con
cent
ratio
n ug
/m3
2X Method Volume Reported Air Concentration
HG0014HG0014AHG0015HG0015AHG0016HG0016AHG0017HG0017AHG0018HG0018AReport Limit
Results - 3X method volume
• Good agreement with spiking study• Very consistent recovery across multiple
samples– 0.22-0.25 ug
• Very consistent air concentrations– 0.72 - 0.83 ug/m3
0.0000
0.0500
0.1000
0.1500
0.2000
0.2500
Rep
orte
d M
ass
ug3X Method Volume Reported Mass
HG0004HG0004AHG0005HG0005AHG0006HG0006AHG0007HG0007AHG0008HG0008AReport Limit
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
Air
Con
cent
ratio
n ug
/m3
3X Method Volume Reported Air Concentration
HG0004HG0004AHG0005HG0005AHG0006HG0006AHG0007HG0007AHG0008HG0008AReport Limit
Discussion
• Method appears to work for volumes up to 300L
• Significant limitations include extended sampling time, battery life
• More samples required before a valid statistical analysis can be done
• May be acceptable to regulators requiring an agency method
Helpful Links• ATSDR Toxicological Profile - Mercury;
http://www.atsdr.cdc.gov/toxprofiles/tp46.html
• NIOSH Method 6009;http://www.cdc.gov/niosh/nmam/pdfs/6009.pdf
• OSHA Safety and Health Topic - Mercury;http://www.osha.gov/dts/chemicalsampling/data/CH_250510.html