The ECETOC “young scientist‘ award at X2012 (7th International Conference on the Science of Exposure Assessment, organised by the British Occupational Hygene Society) was awarded to Katleen de Brouwere from Vito in Belgium for her paper “mechanistic risk assessment of indoor air pollutants: exposure to phthalates‘. Katleen successfully applied the methodology developed in the context of TAGS by Dr Alberto Gotti and Dr Spyros Karakitsios of CERTH (GR). The X2012 jury all agreed that Katleen‘s paper was of a very high standard and that the concepts she addressed (which arise from the CEFIC-LRI supported TAGS project) take the science of multi source, multi pathway consumer exposure and risk assessment to a new level. Indeed there was much subsequent discussion on how the concepts might also be applied to worker and environmental exposures.
Katleen de Brouwere (Vito, Belgium) and Chris Money (ExxonMobil)
For more information on the 7th International Conference on the Science of Exposure Assessment, visit www.x2012.org
Given the multitude of phthalates originating from sources in the indoor environment, their usage patterns and routes of exposure, an aggregate, multi-pathway exposure approach is needed for the evaluation of systemic health effects. To this end, the methodology and online tools developed within the INTERA project were used (http://intera-home.eu/). The INTERA knowledge management system hosts data libraries of exposure factors for the EU population, namely, 1) concentrations and release rates of phthalates in consumer products, 2) behavioral factors (usage and time activity patterns, mouthing behavior,â€¦) , and 3) physiological factors (inhalation rates, body weight, skin surface area,â€¦). These databases were linked to the INTERA computational platform which provides a full-chain modeling tool to calculate exposure starting from emissions up to concentrations in the human body. In addition to the use of absorption factors for each pathway to calculate aggregate exposure, the model also includes a PBPK model describing the dynamics of the fate of DEHP in the human body.
Indoor exposures to DEHP, BBzP, DINP and DIDP in the EU population, split up into several subpopulations (e.g. infants 0-1 year; toddlers 1-3 year; adults ) were modeled using the INTERA methodology and tools.
The European average aggregate exposure to DEHP in the indoor environment is more than 10-fold higher for infants than for adults (infants: 7.4 Î¼g/day/kg bw ; adults: 0.5 Î¼g/day/kg bw). Similar differences in aggregate exposure between these groups were found for BBzP, DIDP and DINP.
Infants‘ exposure to DEHP in the indoor environment was dominated by oral exposure via mouthing toys and other plastic objects (40 %) and by unintentional ingestion of dust (35 %). Dermal contact contributed to about 24 % of the systemic dose for DEHP, while dermal contact with dust was negligible; inhalation contributed only marginally (0.7 %) to the systemic dose for DEHP.
The model predictions were validated by means of independent data at various stages of the modeling chain. There was a good match between predicted concentrations in settled house dust (717 mg DEHP/kg dust) and measured data (210 â€“ 1050 mg DEHP/kg dust) (Kolarik et al., 2008; Langer et al., 2010). In addition, predictions of metabolites of DEHP in urine (MEHP: 1.4 ng/ml) fell in the same order of magnitude as reported averages from biomonitoring studies in the literature (MEHP in urine: 4 â€“ 10 ng/ml) (Wittassek et al., 2011) . Not surprisingly, biomonitoring data are higher than predictions since the latter do not include dietary intake which is a significant pathway for DEHP.
The findings from this case study demonstrate the use of the INTERA tools for indoor exposure assessment for chemicals with multiple sources and pathways, and with complex dynamics between gas and settled phase.
Acknowledgement: Project funded by CEFIC contract LRI-B4 THL (Brussels, 2009)
Kolarik B, Bornehag CG, Naydenov K, Sundell J, Stavova P, Nielsen OF. 2008. The concentrations of phthalates in settled dust in Bulgarian homes in relation to building characteristic and cleaning
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Langer S, Weschler CS, Fischer A, Bekö G, Toftum, Clausen G. 2010. Phthalate and PAH concentrations in dust collected from Danish homes and daycare centers. Atmospheric Environment 44: 2294-2301.
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