s. gagné
TRANSCRIPT
Évaluation adéquate d’aérosols de diisocyanate-4,4’ de diphénylméthane (MDI) à partir d’un CIP10
Sébastien Gagné, M. Sc., Chimiste Membre titulaire Society of Toxicology Membre titulaire de la Société de toxicologie du Canada Co-auteur: Silvia Puscasu, Simon Aubin, Yves Cloutier, Philippe Sarazin et Huu Van Tra
Introduction – 4,4'-methylene diphenyl diisocyanate (pMDI)
• pMDI is used for spray foam application in a ratio of ≈50%monomer/50%oligomers.
• pMDI monomer and oligomers are strong sensitizers and respiratory and cutaneous irritants.
• The main consequence of work-related overexposure to pMDI is occupational asthma.
• Occupational Exposure Limit (OEL) of 5 ppb for MDI monomer in air adopted by most countries.
• The toxicity of the total isocyanate functional groups must be considered, since oligomers induce asthma as much as monomers.
• The monomer and oligomers must be derivatized during sampling and further analyzed in the laboratory.
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Introduction – Sampling devices used for isocyanates
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Efficiently collects MDI monomer and oligomer aerosols
Risk of fire and explosion
Not practical for personal sampling (spillage)
Well accepted by OSH community for NCO monomer and oligomer sampling
Easy to use and solvent-free (Field desorption needed)
Underestimate the level of MDI measured vs impinger in fast curing applications
Impinger Filters ASSET™ EZ4-NCO Easy to use for NCO
sampling and solvent-free
No MDI oligomer analytical method published
Sampling efficiency not characterized for pMDI spray foam insulation
The sampling devices available are limited for safe and efficient MDI aerosol sampling
Introduction – Current needs for MDI aerosol sampling
• Safe sampling device • Avoids volatile and flammable solvent usage • Compatible with personal sampling
• Efficient sampling device
• Provides MDI monomer and oligomer aerosol concentrations comparable to the impinger in pMDI spray foam insulation
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Introduction – Additional sampling devices available
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CIP10
CIP10M
• Safe and designed for personal sampling • Different configurations available
• CIP10: Dust • CIP10M: Microorganisms
• Sampling rate of 10L/min with a sampling
efficiency of >95% (a.d. = 2.8 µm)*
• Never used for isocyanate aerosol sampling
* Gorner, P. et al., (2006) J. Environ. Monit., 8(1): 43-48
Objectives
• Adapt the CIP10 technology for pMDI aerosol sampling in spray foam insulation • Develop the laboratory method and establish analytical performances
• Compare the CIP10 with impinger and ASSET for pMDI aerosol
sampling in spray foam insulation
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CIP10 adaptation
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• Use the CIP10M configuration • Good theoretical sampling efficiency for pMDI
aerosol (a.d. ~10 µm) • Replace the aqueous medium with a non-
volatile co-solvent • Low viscosity to allow easy centrifugation
• Add derivatization agent
1-(2-Methoxyphenyl)piperazine (MOPIP) in the co-solvent compatible with HPLC-PDA detection
CIP10 adaptation – Co-solvent selection
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• Non-volatile polymer
• Require a liquid/liquid extraction (LLE) prior to HPLC-PDA analysis
• Easily miscible with MOPIP
• Non-volatile and non-flammable solvent with a high boiling point (293oC)
• Easily dissolves MOPIP
• No LLE required prior to HPLC-
PDA injection
Dimethylpolysiloxane (DMPS) Tributylphosphate (TBP)
Method’s analytical performances with DMPS
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Analytical parameters MDI-MOPIP monomer derivative
LOD 0.010 μg/ml
LOQ 0.033 μg/ml Dynamic range 0.079 μg/mL (10% OEL) to
0.787 μg/mL (100% OEL) R2 >0.990
Intra-day precision 4%
Inter-day precision 4%
Recovery (matrix effect) 98 ± 4%
Accuracy 100 ± 6%
• The method’s analytical performances established in the laboratory meet expectations • The analytical performances are similar with TBP (data not shown) • The method is judged suitable for field evaluations
Sample loss evaluation in CIP10M
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0%
20%
40%
60%
80%
100%
120%
140%
0 min 10 min 30 min 60 min
% r
ecov
ery
Time
DMPS 10L/min
DMPS 7L/min
TBP 10L/min
• Sample loss is avoided with TBP • TBP is the co-solvent selected for the field comparison
Field evaluation – Confined atmosphere
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4 m
3.1
m
• 2 panels on which the pMDI foam is sprayed
• Samples are collected inside and outside the jar using impingers to assess set-up reproducibility
• The set-up has been judged reproducible (data not shown)
• Demilec Airmetic Soya • Demilec Isocyanate A100 • Sampling: ~25 minutes • Layer: ~1’’ • Total applications: 5/panel • Concentration: ~50-150% OEL
Field evaluations – Jar
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• Jar dimension • Diameter: 17½ inches • Height: 25½ inches • Orifice diameter: 4 inches • Chimney height: 15½ inches • Sampler attached 16 inches from the bottom • Fan sucking at 8 inches/sec
• Compatible with all sampling devices
• Up to 10 devices can run in parallel at
variable flow rate
• Designed to allow a homogenous atmosphere
Field comparison – CIP10M vs impinger
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• The MDI monomer concentrations provided by the CIP10M sampling method were in the same range than the ones provided by the impingers
• Overall 14% lower (95% approximate confidence interval (CI) 2-26%) • A bias of 14% is considered very low compared to the typical environmental variability observed in
exposure data in workplaces • When restricting the analysis to days one and two, the results show that the two sampling methods
(i.e., CIP10M vs impingers) provided comparable results (difference of 0% (95% CI -15 to 15%)).
pMDI monomer
Field comparison – CIP10M vs impinger
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pMDI oligomers
• The CIP10M provided higher concentrations than the impingers • approximately two times greater (difference of 94% (95% CI 76-113%)) than the ones provided by
the impingers • This difference cannot be interpreted because even if the impinger were chosen as the reference method,
the absolute recovery for MDI oligomers has never been formally established for this sampling technique. • The amount of oligomers detected agrees with the formulation of the foams used. The CIP10M appears to
be more efficient than the impingers for the collection of MDI oligomers
Field comparison – ASSET EZ4-NCO vs impinger
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pMDI monomer pMDI oligomers
• The ASSET EZ4-NCO:
• Significantly underestimated the MDI monomer and oligomers concentrations
• The ASSET sampler is currently used by some laboratories for pMDI quantitation in fast curing application despite these results
Conclusion
• The sampler efficiency must be assessed in the field as early as possible during method development and must be characterized for each different application
• The use of a CIP10 containing TBP as the co-solvent seems promising for
pMDI aerosol sampling in spray foam insulation
• The ASSET sampler significantly underestimated the MDI concentrations vs the impinger in spray foam insulation
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Future work
• Evaluate the CIP10M configuration now supplied • Currently, the configuration from 2006 is used
• Evaluate the sampler in a real situation in the field
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Acknowledgements
• Lucile Richard – laboratory and field sampling
• Claude Letourneau and Pierre Drouin – jar construction • Jacques Lesage - invaluable advice
• Isolation Majeau et frère – field sampling
• IRSST and UQAM - instrumental and financial support
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Questions
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