Load and Level CLL approach for assessment of ecosystem risks

Critical loads and levels are measurable quantitative estimates showing the degree of tolerable exposure of receptors to one or more pollutants. According to present knowledge, when this exposure remains below the critical load and level thresholds, significant harmful effects on specified receptors do not occur (Gregor, 2003). They serve as reference points against which pollution levels can be compared and potential risks to environmental components can be estimated. 

Over time, there has been growing interest in defining critical loads at a regional level to define sensitivity of particular areas to inputs of pollutants and to set specific 

The latest advances and trends in developing the CLL concept, which has been constantly validated and progressively improved since its international authorization in 1988 (Cresser, 2000), have encouraged the author to consider if critical loads and their exceedances could be used in El A for assessing effects on ecosystems. 

The following strengths of the CLL approach in the context of EcoRA/EIA are summarized below. 

Quantitative nature of the CLL approach. Numerical tolerable exposure levels for pollutants of concern are defined to establish quantitative thresholds for risk characterization therefore the CLL approach provides a basis for quantitative ecosystem risk and damage assessment. 

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