Table 4.

Summary of MDI exposure studies for the main processes.

Sector	Study populations (country, no. workers)	Biomonitoring data [expressed as range (median)]	Notable correlations/comments	LaKind scoringa	References
(Rigid) foam production	Finland, n = 57	Urine: 0.015–1.4 (0.13) µmol mol−1 cr. Plasma: 1.8–2.6 µg l−1 18–37 pmol g−1 (Hb)	Airborne levels (very low or not detected) and task time not associated with urinary biomarker levels.	13	Säkkinen et al. (2011)
	Sweden, n = 18	Urine: 0.5–8.4 µg l−1 [~0.2–3.5 µmol mol−1 cr.] Plasma: 0.4–19.4 µg l−1	Plasma and urinary MDA correlated after 2 days of no exposure (P > 0.986).	12 Creatinine and specfic gravity	Tinnerberg et al. (2014)
PUR industry (generic)	France, n = 169 (19 factories)	Urine: <0.1–23.6 µg l−1 [<0.5–19.25 µmol mol−1 cr.]	Association with skin exposure. Elevated pre-shift levels but not cumulative. Higher MDI % in formulations not associated with higher results.	13 Both raw and corrected data	Robert et al. (2007)
	Sweden, n = 18	Urine: 0.3–78 (2) µg l−1 [~0.13–32.7 (0.8) µmol mol−1 cr.] Plasma: 0.2–74 (0.7) µg l−1	Weak but significant correlations with air. P < 0.01 (U), P < 0.05 (P)	12 Both raw and corrected data	Sennbro et al. (2006)
	UK, n = 71	Urine: <0.5–0.7 µmol mol−1 cr. (only 6+ve/71 results above LoD)	Low levels of isocyanate exposure in the PUR elastomer industry.	11	Cocker et al. (2009)
	UK, n = 90	Urine: 56/326 > LoD, 90% 0.5 µmol mol−1 cr. (median < LOD)		12	Keen et al. (2012)
	Finland, n = 21	Urine: <0.01–3.1 µmol mol−1 cr.	Low exposures but highest levels seen in pipe layers.	11	Rosenberg et al. (2002)
PUR industry (glue)	Sweden, n = 150	Urine: <LoD–1.8 µg l−1 [~<LoD–0.8 µmol mol−1 cr.] <LoD-9.4 (heat) µg l−1	Higher exposure levels when using heated glue.	11 External QA	Littorin et al. (2000)
Construction	Switzerlandb, n = 65	Urine: MDA 0.003–3.2 µg l−1 [~0.001–1.3 µmol mol−1 cr.] Median (P90) Hb-MDA: 0 (0.177) pmol g−1 Hb Hb-AcMDA: 2 positive, 2.3 and 3.7 pmol g−1 Hb	U-MDA-tot correlates with U-AcMDA and Hb-MDA with r = 0.86 and r = 0.39, respectively (P < 0.01). U-AcMDA correlates with Hb-MDA with r = 0.47, (P < 0.01). U-MDA correlates with Hb-MDA (r = 0.38, P = 0.05).	14 Methodology not well described	Sabbioni et al. (2007)
	Switzerlandb, n = 65	Albumin: MDI-Lys 0–899.4 fmol mg−1 AcMDI-Lys: 0–51.2 fmol mg−1	Correlation MDI-Lys with MDA-Hb, r = 0.295 (P < 0.05) Same workers as Sabbioni et al. (2007) MDI-Lys levels were compared in a subgroup of construction workers (n = 19) which were analysed prior to isocyanate exposure and after 4–7 months of isocyanate exposure; the MDI-Lys levels increased significantly (Wilcoxon sign test, P < 0.01).	12	Sabbioni et al. (2010)
	Finland, n = 21	Urine: <0.1–0.2 µmol mol−1 cr. Dermal: 88% <2 µg MDI 10 cm−2 on hand	Effect of RPE lowering exposure seen in post-shift samples but not evening and following morning samples indicating 2 routes of exposure, dermal and inhalation.	12 Both raw and corrected data	Henriks-Eckerman et al. (2015)
Other	Switzerlandbn = 27 (chemical industry)	Urine: MDA 0–10.2 (1.7) nmol l−1 [~0–0.9 (0.142) µmol mol−1 cr.] Albumin: MDI-Lys 0–138 pmol g−1 AcMDI-Lys: 25.6 pmol g−1 (1 +ve)	Correlation MDI-Lys with MDA-Hb, r = 0.382 (P < 0.05).	12	Sabbioni et al. (2010)
	Switzerland, n = 73 (urethane mould production)	Albumin: MDI-Lys = 191 pmol g−1 (mean) (based on 4 workers with asthma who reported that their last activity with MDI was >3 months ago) MDI-Lys = 750 pmol g−1 (mean) (n = 5)	Workers with confirmed asthma had significantly higher adduct levels than healthy worker.	14 Methodology not well described	Sabbioni et al. (2017)
	Germanyb, n = 25	Urine: <500–124 490 pmol g−1 creatinine [0.004–1.1 µmol mol−1 cr.] Hb: MDA <0.35–1.12 pmol g−1 ABP-Val-Hyd 0.15–16.2 pmol g−1	No exposure assessment; measurement of Hb adducts and ABP-Val-Hyd reflect long term exposure (up to 120 days)	12	Gries and Leng (2013)

^aThe lower the LaKind score the better the overall quality (possible range 8–24).

^bCountry of origin assumed from authors’ affiliation, not specifically stated in paper.