Traditional risk assessments of chemicals are failing to protect the environment
Regulatory decisions based on current risk approaches are flawed simply because the science underpinning the risk of chemicals is inappropriate in many cases. A fundamental problem is to use one methodology for all compounds, irrespective of their toxic mode of action in organisms. According to the theories of Druckrey and Küpfmüller, the character of a poison is primarily determined by the reversibility of critical receptor binding. Chemicals showing irreversible or slowly reversible binding to specific receptors will produce cumulative effects with time of exposure, and whenever the effects are also irreversible (e.g. death) they are reinforced over time; these chemicals have time-cumulative toxicity.This concept was validated by Druckrey and co-workers with genotoxic carcinogens, the action of which is described by what is now known as the Druckrey-Küpfmüller equation: c x t˄n = constant, where c = exposure concentration, t = median time to effect, and n is an exponent > 1, which reflects reinforcement of the effect over time. Using data generated by Sanchez-Bayo, Tennekes demonstrated that the Druckrey-Küpfmüller equation also described the toxicity of (non-genotoxic) neonicotinoid insecticides to arthropods. This discovery showed that the theories of Druckrey and Küpfmüller were generally applicable in toxicology and, perhaps even more importantly, that risk assessment procedures needed to be revised, because the risks of time-cumulative toxins had been seriously underestimated.