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Erin Dickison

Biological monitoring is one of the most accurate approaches for measuring true body burden (actual exposure) from exposure to substances and can be used along with exposure monitoring. Biomonitoring is a scientific technique for assessing human exposures to natural and synthetic chemicals based on sampling and analysis of an individual's tissues and fluids, usually urine and/or blood. It identifies certain substances in the body (Biomarker) at the time of measurement. A biomarker can be the substance itself or a metabolite. In the workplace, information collected from biomonitoring helps occupational health and safety professionals (occupational health physicians, industrial hygienists, epidemiologists, toxicologists, etc.) to determine whether current protective measures are adequate to limit exposures.

A biomarker should be specific – preferably measuring only the substance in question. The chemical reactivity of diisocyanates precludes measurement of free diisocyanates in humans. The current occupational biomonitoring method used for diisocyanates involves hydrolysis of urine and measurement of the diisocyanate hydrolysis product (amine). However, this method is not very specific and cannot distinguish hydrolysis of the diisocyanate from concurrent exposure to the amine.

A biomonitoring method should be sensitive and have sufficient ability to identify positive results, therefore to measure low levels that may be relevant to workplace exposures at or below current occupational exposure limits. The method should also be standardized to allow for comparability across laboratories. In addition, the method should show a relationship between measured results and possible exposure concentrations to determine if an occupational exposure limit has been exceeded.

Various research projects are currently being undertaken to identify a ‘Biomarker’ that is specific to the diisocyanates and displays relevant sensitivity. See the Additional Resources to obtain some references on current research.

When considering results from any biomonitoring analysis, it is important to recognize that the detection of a substance in the body indicates only that an exposure has taken place; it does not indicate an adverse health effect. This point is underscored by the U.S. Centers for Disease Control and Prevention (CDC): “Just because people have an environmental chemical in their blood or urine does not mean that the chemical causes disease1.”

Diisocyanates and The Human Body

Exposure to diisocyanates is unlikely. From this review of the biological transformation process, we can see that in addition to worker protections that limit exposure to diisocyanates, our natural defense systems have the capability to mitigate potential toxic effects whenever exposure might occur. Meanwhile, continuous safe use of diisocyanates allows us all to benefit from their many positive applications in our lives.

Additional Resources

  • The American Chemistry Council provides general information about the role Biomonitoring can play in helping protect public health and in making informed policy-decisions. For additional information about diisocyanate workplace monitoring methods and reporting, visit the Industrial Hygiene or the Air Monitoring sections. For information about diisocyanate environmental monitoring, including EPA Testing Methods and stack emissions testing, visit the Environmental Emissions Reporting and Testing section.
  • Bhandari D, Ruhl J, Murphy A, McGahee E, Chambers D, Blount BC. 2016. Isotope Dilution UPLC-APCI-MS/MS Method for the QuantitativeMeasurement of Aromatic Diamines in Human Urine: Biomarkers of Diisocyanate Exposure. Anal. Chem. 88: 10687−10692.
  • Hettick, J.M. and P.D. Siegel. Determination of the toluene diisocyanate binding sites on human serum albumin by tandem mass spectrometry. Analytical Biochemistry 414(2): 232-238, 2011
  • Leng G, Gries W. 2017. New specific and sensitive biomonitoring methods for chemicals of emerging health relevance. International Journal of Hygiene and Environmental Health 220: 113–122
  • Ruwona TB, Johnson VJ, Hettick JM, Schmechel D, Beezhold D, Wang W, Simoyi RH, Siegel PD. 2011. Production, characterization and utility of a panel of monoclonal antibodies for the detection of toluene diisocyanate haptenated proteins. J Immunol Methods. Oct 28;373(1-2):127-35
  • Sabbioni G, Dongari N, Kumar A. 2010. Determination of a new biomarker in subjects exposed to 4,4’-methylenediphenyl diisocyanates. Biomarkers, 15(6): 508–515
  • Sabbioni G, Gu O, and Vanimireddy LR. 2012. Determination of isocyanate specific albumin-adducts in workers exposed to toluene diisocyanates. Biomarkers, 17(2): 150–159
  • Säkkinen K, Tornaeus J, Hesso A, Hirvonen A, Vainio H, Norppa H, Rosenberg C. 2011. Protein adducts as biomarkers of exposure to aromatic diisocyanates in workers manufacturing polyurethane (PUR) foam. J Environ Monit. 13(4):957-65.

1 Centers for Disease Control and Prevention. Second National Report on Human Exposure to Environmental Chemicals.CDC; 2003. p.2.

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