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Air exposure assessment of TDI and biological monitoring of TDA in urine in workers in polyurethane foam industry
  1. Tom Geens1,
  2. Sandra Dugardin1,
  3. Ann Schockaert1,
  4. Geert De Cooman1,
  5. Marc van Sprundel2
  1. 1Provikmo Occupational Health Services, Bruges, Belgium
  2. 2Department of Epidemiology and Social Medicine, University of Antwerp, Antwerp, Belgium
  1. Correspondence to Dr Tom Geens, Provikmo Occupational Health Services, Dirk Martensstraat 26/1, B-8200 Bruges, Belgium; tom.geens{at}


Objectives Toluene diisocyanate (TDI) is used in the manufacturing process of polyurethane (PU) foams and is a potent inducer of occupational asthma. The objective of this study was to evaluate the correlation between the exposure to total TDI (2,4- and 2,6-TDI) in air and the corresponding biomarker concentration of total TDA (2,4- and 2,6-TDA) in hydrolysed urine. The aim was also to propose an appropriate biological exposure limit for total TDA in urine.

Methods 9 workers from two production lines in a PU foam producing plant were studied. Personal exposure to TDI during four representative production shifts was monitored by an active air sampling method (filter impregnated with 1-(2-methoxyphenyl)piperazine) and quantified by high-performance liquid chromatography and diode array detection (NIOSH n° 2535, 5521). In parallel, pre-shift and post-shift urinary samples were collected from the exposed workers, and TDA concentrations were determined by gas chromatography–mass spectrometry after alkaline hydrolysis. All samples were collected on four measuring days: two Fridays (end of workweek) and two Mondays (start of workweek) separated by a weekend without exposure.

Results Strong correlations between the personal air concentrations of total TDI and the corresponding biomarker levels of total TDA in urine (r=0.816) were observed. An increase of 18.12 μg TDA/l (post-shift minus pre-shift concentration) corresponds to an exposure of 5 ppb (37 μg/m3, the current American Conference of Governmental Industrial Hygienists threshold limit value) during the shift.

Conclusions The increase in TDA during the shift is a suitable biomarker for exposure to TDI during the same shift. Further research is needed to evaluate the use of start of week or end of week post-shift TDA in urine as biomarker since TDA was found to accumulate during the working week and thus the moment of sampling will clearly influence the result.

  • TDI
  • exposure assessment
  • TDA
  • biomonitoring
  • biological monitoring
  • hygiene/occupational hygiene
  • toxicology

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  • Funding TG and SD were financially supported by Provikmo to conduct this study. The workers agreed to participate for free in the study.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.