Assessing burden of disease as disability adjusted life years in life cycle assessment.

Disability adjusted life years (DALYs) have been used to quantify endpoint indicators of the human burden of disease in life cycle assessment (LCA). The purpose of this paper was to examine the current use of DALYs in LCA, and also to consider whether DALYs as used in LCA have the potential to be compatible with DALYs as used in quantitative risk assessment (QRA) to facilitate direct comparison of the results of the two approaches. A literature review of current usage of DALYs in LCA was undertaken. Two prominent methods were identified: ReCiPe 2008 and LIME2. The methods and assumptions used in their calculations were then critically reviewed. The assumptions used for the derivation of characterization factors in DALYs were found to be considerably different between LCA methods. In many cases, transparency of these calculations and assumptions is lacking. Furthermore, global average DALY values are often used in these calculations, but may not be applicable for impact categories where the local factors play a significant role. The concept of DALYs seems beneficial since it enables direct comparison and aggregation of different health impacts. However, given the different assumptions used in each LCA method, it is important that LCA practitioners are aware of the differences and select the appropriate method for the focus of their study. When applying DALYs as a common metric between LCA and QRA, understanding the background information on how DALYs were derived is crucial to ensure the consistency of DALYs used in LCA and QRA for resulting DALYs to be comparable and to minimize any double counting of effects.

Global and local health burden trade-off through the hybridisation of quantitative microbial risk assessment and life cycle assessment to aid water management.

Life cycle assessment (LCA) and quantitative risk assessment (QRA) are commonly used to evaluate potential human health impacts associated with proposed or existing infrastructure and products. Each approach has a distinct objective and, consequently, their conclusions may be inconsistent or contradictory. It is proposed that the integration of elements of QRA and LCA may provide a more holistic approach to health impact assessment. Here we examine the possibility of merging LCA assessed human health impacts with quantitative microbial risk assessment (QMRA) for waterborne pathogen impacts, expressed with the common health metric, disability adjusted life years (DALYs). The example of a recent large-scale water recycling project in Sydney, Australia was used to identify and demonstrate the potential advantages and current limitations of this approach. A comparative analysis of two scenarios - with and without the development of this project - was undertaken for this purpose. LCA and QMRA were carried out independently for the two scenarios to compare human health impacts, as measured by DALYs lost per year. LCA results suggested that construction of the project would lead to an increased number of DALYs lost per year, while estimated disease burden resulting from microbial exposures indicated that it would result in the loss of fewer DALYs per year than the alternative scenario. By merging the results of the LCA and QMRA, we demonstrate the advantages in providing a more comprehensive assessment of human disease burden for the two scenarios, in particular, the importance of considering the results of both LCA and QRA in a comparative assessment of decision alternatives to avoid problem shifting. The application of DALYs as a common measure between the two approaches was found to be useful for this purpose.