An Update of the Human Toxicity Potential with Special Consideration of Conventional Air Pollutants

We present updated values for the Human Toxicity Potential (HTP) of 349 pollutants. The HTP is a characterization method used to weight emissions, such as those listed in life-cycle inventories and toxic release inventories. HTP is a screening-level risk indicator that accounts for both toxicity and the potential to result in exposure, but that does not account for regional differences or variations in population density. This paper introduces new calculations for conventional air pollutants, which also account for the oxidation products of SO2 and NOx, which are more dangerous than the primary pollutants. For the first time, we take into account the scale of mixing in the atmosphere. Calculations are presented for emissions to air, surface water, as well as to agricultural and non-agricultural soil at two different soil depths. This update also reflects changes in the underlying toxicity data. Because sulfur dioxide and nitrogen oxides are ubiquitous and emitted in large amounts, this update has a significant impact on life cycle assessment results.