An impact category indicator is a quantifiable representation of an impact category endpoint. This term serves as a fundamental concept in Life Cycle Impact Assessment (LCIA), providing the means to measure and express potential environmental impacts in concrete, comparable units.
According to ISO 14040, an impact category indicator represents a "quantifiable representation of an impact category endpoint". The emphasis on "endpoint" is crucial, as it clarifies that the indicator must ultimately relate to the final point of concern in the cause-effect chain of environmental impacts. This endpoint typically represents an attribute or aspect of the natural environment, human health, or resources that society seeks to protect.
Impact category indicators transform the results from Life Cycle Inventory analysis into meaningful environmental metrics. For example, in climate change assessment, the impact category indicator might be expressed in kilograms of CO₂ equivalents, which quantifies the potential contribution to global warming. For human health impacts, indicators such as Disability-Adjusted Life Years (DALYs) provide a standardised measure of health burden.
The selection and definition of impact category indicators follows characterisation models that describe the relationship between life cycle inventory results and their subsequent impacts as represented by the impact category endpoints. Each indicator must be scientifically robust, allowing practitioners to calculate the magnitude of potential environmental impacts associated with a product system throughout its life cycle.
By providing quantifiable representations, impact category indicators enable comparison between different product systems, identification of environmental hotspots, and informed decision-making in product development and policy contexts. They serve as the bridge between raw inventory data and actionable environmental insights.
