Transformation products in the life cycle impact assessment of chemicals

The current life cycle impact assessment (LCIA) of chemicals focuses only on the fate and effects of the parent compound, neglecting the potential impact of transformation products. Here, we assess the importance of including the potential impact of transformation products in the calculation of characterization factors (CF). The developed method is applied to freshwater ecotoxicity for 15 pesticides and perchloroethylene, which are all known to have potentially persistent transformation products. The inclusion of transformation products resulted in a median increase in CF that varied from negligible to more than 5 orders of magnitude. This increase, however, can be highly uncertain, particularly due to a lack of toxicity data for transformation products and a lack of mode of action-specific data. We show in a case study that replacement of atrazine with other pesticides for application on corn results in a median impact score of 2 orders of magnitude lower when the fate and effects of only the parent compounds are included. When transformation products are included, the reduction in median impact score would likely be lower (less than 1 order of magnitude). An uncertainty analysis showed that the difference in impact scores of atrazine and the atrazine replacements was not statistically significant when only the parent chemical was considered. When transformation products were included, the uncertainty in impact scores was even greater.