title: Air exposure assessment of TDI and biological monitoring of TDA in urine in workers in polyurethane foam industry.
abstract: OBJECTIVE
  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/m(3), 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.
authors: Provikmo Occupational Health Services, Dirk Martensstraat 26/1, B-8200 Bruges, Belgium. tom.geens@provikmo.be
authors: Tom
authors: T
authors: Geens
authors: Sandra
authors: S
authors: Dugardin
authors: Ann
authors: A
authors: Schockaert
authors: Geert
authors: G
authors: De Cooman
authors: Marc
authors: M
authors: van Sprundel
mesh_terms: D000395:Air Pollutants, Occupational / Q000009:adverse effects / Q000652:urine*; D059366:Asthma, Occupational / Q000209:etiology / Q000652:urine*; D015415:Biomarkers / Q000652:urine; D002617:Chemical Industry; D004784:Environmental Monitoring / Q000379:methods*; D006801:Humans; D016273:Occupational Exposure / Q000032:analysis*; D009790:Occupations; D010655:Phenylenediamines / Q000652:urine*; D011140:Polyurethanes; D012016:Reference Values; D014051:Toluene 2,4-Diisocyanate / Q000009:adverse effects / Q000032:analysis*
chemical_list: D000395:Air Pollutants, Occupational; D015415:Biomarkers; D010655:Phenylenediamines; D011140:Polyurethanes; D014051:Toluene 2,4-Diisocyanate; C025235:2,6-diaminotoluene