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From biological models to contaminant risks: How to unravel the mystery of environmental risks?
In today's society, with the rapid development of industrialization, the synthesis of new chemicals is increasing, and the potential harm of these chemicals to human health and the environment has become a problem that needs to be solved urgently. Environmental risk assessment, as a scientific measure, can help decision makers provide a scientific basis for the protection of public health and the ecological environment when facing these emerging pollutants. Although different ways of measuring pollutant concentrations, such as the "no observed adverse effect level" (NOAEL) and "exposure level", are controversial, their importance cannot be ignored.
No Effect Concentration (NEC) and No Observed Effect Concentration (NOEC)
The no-effect concentration (NEC) is an important parameter in risk assessment and is defined as the concentration of a pollutant that will not cause harm to the species in question under the specific impact being studied. This concept provides a starting point for the development of environmental policies. In practice, scientists typically determine this concentration through standard tests, which involve dividing groups of animals, exposing them to different concentrations of a chemical, and monitoring different effects such as survival, growth or reproduction.
However, this no-observed-effect-concentration (NOEC) method has been subject to much criticism in statistics, and many scholars believe that this concept should be abandoned.
ECx Proposals and Challenges
As an alternative to NOEC, ECx (effect concentration) came into being. ECx represents the specific effect ratio at a certain concentration (for example, EC50 means that 50% of the test animals in the experiment will die). However, this approach also faces difficulties when applied to risk assessment. Because any value of x other than zero could lead people to mistakenly believe that this is an acceptable effect, which goes against the overarching goal of protecting the environment.
In addition, the ECx value also depends on the exposure time. The longer the exposure time, the ECx value of its lifetime will gradually decrease until it reaches equilibrium. This is because the effect depends on the internal concentration, which takes time.
Biologically based approaches
Biologically based risk assessment approaches seek not only to describe observed effects but also to understand their underlying processes, such as toxicokinetics, mortality, feeding, growth, and reproduction. This approach starts with the uptake and elimination of the compound in the organism, because the main effects only occur after the compound enters the body.
Therefore, the use of NC as one of the model parameters can more flexibly reflect the impacts of multiple stressors and take into account multiple processes such as adaptation, population dynamics and life cycle phenomena under real field conditions.
Limitations of Standard Testing Procedures
It is important to note that standard testing procedures usually keep the local environment constant, thus eliminating the influence of multiple stressors. This is among the parameters that primarily affect survival and reproduction, which are needed to predict effects on populations growing in the wild.
Challenges Ahead
How to more effectively apply these biological models to the risk assessment of pollutants will be an important challenge to be faced in the future. Environmental scientists and policymakers must work together to ensure that the findings from scientific research are translated into effective governance strategies to protect our ecosystems and human health.
After reading this article, have you ever thought about whether future pollutant risk assessments can better balance the contradiction between ecological protection and industrial development?
