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Fiber Escape from Asbestos Abatement Enclosures -
Quantitative ResultsPaul Bozek, PEng CIH ROH
Andrea Sass-Kortsak, PhD CIH ROH
PO 131 Industrial Hygiene General Practice
Background - AbatementContainment in “Type 3” Indoors:
Background - Abatement• Fiber level inside removal enclosures are
well known and studied• Fiber levels outside enclosures are not• Limited, published, old data suggests fiber
levels outside can be elevated, depend* on• Poor worker decontamination procedures• Insufficient negative pressure inside enclosures• Problems with negative air machines/filters
* Applied OEH 13(1) p 32, 1998
Study Method
• Observe practices /take pairs of air samples in Type 3 abatement projects (N=23) during:• Abatement (cutting, scraping, etc)• Worker decontamination at breaks• Asbestos Waste removal from enclosure
• NIOSH 7400 (PCM): 20 min to 1 hour, dependent on task
• Air samples are short term samples, not TWA!
• Gather data on project:• # workers, pressures, type of ACM, size
Study Method – Data
• Assumption for “overloaded samples”• Use air volume and NIOSH 7400 max fibre density
• Assumption for None detected (“ND”)• Use air volume and ½ x lab-specific fibre density LOD
Results
• 21 x “Type 3” Abatement Projects (Indoor)– 2 projects dropped due to short duration– 11 spray-on fireproofing– 4 plaster ceiling/wall removal (non-friable)– 5 friable ACM paper (e.g. “aircell”, sheet )– 2 friable “magblock” plus non-friable cement
• Toronto, Ontario between 2008-2011• Some data missing (due to timing of work)
Results – Observations (1)
• Failure to wet ACM during abatement:N = 5 of 21
• Inadequate negative pressure: • (-5 Pa = -0.02”WG)
– During Abatement , N = 8 of 21– During Garbage removal, N = 6 of 16
Results – Observations (2)
Worker decontamination at breaks or end of shift:• Zero of 21 observed/reported to pre-clean
suits/respirators in the “dirty room” before entering shower
• None had rags/buckets of water nor HEPA vacuums placed in the “dirty room” for this purpose
• Most workers took <1 minute to shower
Results – Observations (3)
Asbestos waste removal from shower or garbage chute:• Zero of 20 observed workers receiving waste
bags wore protective suits/respirators • 8 of 20 observed to be passing out garbage bags
that had not been cleaned (wet wipe or HEPA)• 6 of the 8 observed double bagging in the “dirty
room” but not cleaning the outer bag
“Dirty”Room
Air Results: AbatementMean: 0.65 f/ccMedian 0.39 f/cc10 overloaded Outside Enclosure
Mean: 0.045 f/ccMedian 0.002 f/cc2 overloaded, 9 ND
“Dirty”Room
2 overload2 ND
Air Samples: Worker Decontamination Task
Mean: 0.20 f/ccMedian: 0.03 f/cc
Mean: 0.04 f/ccMedian: 0.03 f/cc3 ND
“Dirty”Room
6 overload1 ND
Air Samples: Garbage Removal Task
Mean: 0.26 f/ccMedian 0.11 f/cc
Mean: 0.013 f/ccMedian: 0.008 f/cc3 ND
Air Samples: Univariate Analyses
Few variables were truly normally distributed• Abatement pressure• Fibre count on dirty side during garbage removal
Log-normal not apparent either• Too few samples?
Non-parametric testing : some correlations significant, mostly relating to garbage removal
Air Samples: Multivariate Analyses - Garbage Removal
Fibre Count - Clean side was a function of (p<0.05)– Fibre Count (dirty side)– Number of workers in project– Negative Pressure– ACM type (non-friable, spray-on, mixed)
Other models (abatement, worker decon) were not significant (p>0.05)
Conclusions
• Observed practices could lead to fibre escape and exposure to those in immediate vicinity of the abatement enclosures, but levels generally acceptable (with some exceptions)
• 3rd party on-site consultants need to observe work practices, not just conduct milestone inspections
Limitations
• Short term tasks = short term sampling• Small dataset• Timing of sampling with respect to tasks variable• High variability of tasks = 21 sites representative?• Assumption for “overloaded samples”• Could be overloaded due to non-fibrous aerosols
Acknowledgements
Co-Investigator: Mike Russo and Enzo GarritanoInfrastructure Health and Safety Assoc. of Ontario
Grant Funding:Workplace Safety and Insurance Board of Ontario