Evaluating Human Health Impacts of Products from a Life Cycle Perspective: Method and Case Studies

The human health impacts of products, especially those may have consumer exposure, is a crucial aspect in product safety assessment. Existing life cycle assessment (LCA) is well established to evaluate products by traditional environmental metrics, such as global warming potential. However, a holistic and comprehensive approach is needed to study the human health impact of products along their life cycle and understand their fate, transport and distribution in the environment. This dissertation illustrated how human health impact assessment (HHIA) could be conducted at product level from a life cycle perspective. This work showed that when advanced environmental engineering modeling tools are combined with LCA in product safety assessment, our understandings of chemical exposure and associated human health risks can be improved. In this research, a method was developed to integrate high resolution air dispersion modeling and LCA to conduct HHIA, using publicly available inventory data. In particular, this method was applied to Methylene Diphenyl Diisocyanate (MDI), a chemical commonly used in building and construction products. It was found that the additional inhalation human health risks were three orders of magnitude lower than the United States Environmental Protection Agency (USEPA)’s risk management threshold. Besides manufacturing stages, this research also evaluated the indoor air quality impact of the spray polyurethane foam (SPF) through industrial hygiene (IH) measurement, lab chamber testing and multi-media mass transfer modeling. The IH study revealed that MDI emitted from SPF decayed rapidly in the indoor environment. Two mass transfer models were employed to study the emission and distribution of Tris(1-Chloro-2-Propyl) Phosphate (TCPP), a flame retardant in SPF, and quantify its human health risks in the indoor environment. Verified by field measurements, the modeling results showed that TCPP was removed from indoor air primarily through indoor-outdoor ventilation, followed by the sorption into indoor diffusional sinks such as drywall. A screening level risk characterization revealed that in this SPF renovated house, TCPP time weighted average ingestion exposure of the most sensitive population (1-2 years old) was below (0.6 µg/kg BW/day) the threshold set by USEPA (10 µg/kg BW/day). The modeling approach is transferable to study other indoor pollutants.