This presentation will be available to view as a discussion poster at the 7th International Conference on the Science of Exposure Assessment - X2012. It will be presented on 03 July 2012 from 13.45 – 15.45 followed by a chaired discussion of all posters in this session on Health Effects and Biological Monitoring. Appointments with the authors are available to book at https://x2012discussionposters.acuityscheduling.com

1. Discrimination of isocyanate exposure from
amine exposure in biological samples
Kate Jones & John Cocker
Health & Safety Laboratory, UK
Abstract
• Isocyanates continue to be one of the leading causes of occupational asthma in the
UK and biological monitoring is a valuable tool in assessing exposure to isocyanates.
• Current methods can be confounded by co-exposure to diamines.
• Isocyanate-specific lysine conjugates have previously been reported using blood
samples – we present some preliminary work looking at urine samples.
• Although further development is necessary, it may be feasible to detect isocyanate-
specific lysine conjugates in urine.
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2. Introduction
• Biological monitoring for isocyanates is
becoming increasingly widespread in the UK.
• Current methods measure the corresponding
amine in urine, after hydrolysis of any
conjugates.
• It has become apparent that there may be
issues distinguishing isocyanate exposures
from amine exposures in cases where either
both are used on-site or the amines are
generated through industrial processes.
• As the hazards of each (isocyanates are
respiratory sensitisers, amines are skin
absorbed and some are carcinogenic) are
different and require different control
solutions, discrimination of the exposures is
required.
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3. Methods
H 2N
Using a previously reported methodology1,
rough standards were prepared by
incubating HDI with human albumin in
physiologically-based saline (37oC, 16 HO NH2
hours). The standards were then
incubated overnight (again at 37oC) with O
pronase E (6 mg/ml) to break down the NH
albumin and release lysine conjugates. NH
O
• Standards and urine samples from exposed workers (previously analysed
for isocyanates by measuring the corresponding amine) were concentrated
and cleaned up using solid phase extraction (Strata X, methanol elution
• Analysis of lysine conjugates was by LC/MS/MS using a Synergi Hydro-RP
column (150 x 2.1mm, 4µ, Phenomenex) with a methanol:ammonium
acetate (10mM with 0.1% acetic acid) gradient. Positive electrospray mass
spectrometry using multiple reaction monitoring was used for detection.
1Sabbioni G, Gu Q, Vanimireddy LR. Biomarkers. 2012;17(2):150-9
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4. Results
1800 0
1600 0
1400 0
1200 0
H D I_ L y s in e ( a r e a )
1000 0
800 0
600 0
400 0
200 0
0
0 50 100 150 200 2 50
T o t a l H D A (n m o l/l)
a) rough standard of HDI-lysine, b) HDA incubated with albumin,
c) positive HDA urine sample, d) non-detected HDA urine sample
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5. Conclusions
• We have demonstrated that HDI can conjugate to albumin and
form a releasable lysine conjugate, which is specific to HDI (the
corresponding amine, HDA, does not form this conjugate).
• Some positive HDA urine samples from HDI-exposed workers
also demonstrate this lysine conjugate. In cases where the lysine
conjugate has been detected there appears to be a correlation
with the total HDA detected in urine.
• Further work is needed using a synthesised and characterised
standard.
• Additional work is ongoing to:
– analyse more samples
– determine whether HDI is bound to albumin or lysine in urine (or
both)
– investigate why some positive HDA samples showed no HDI-lysine
conjugate
– look at other isocyanates (where lysine conjugates have already
been demonstrated by others in blood samples)
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An Agency of the Health and Safety Executive