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