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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