Culmination of Low-Dose Pesticide Effects

Abstract

Pesticides applied in agriculture can affect the structure and function of nontarget populations at lower doses and for longer timespans than predicted by the current risk assessment frameworks. We identified a mechanism for this observation. The populations of an aquatic invertebrate (Culex pipiens) exposed over several generations to repeated pulses of low concentrations of the neonicotinoid insecticide (thiacloprid) continuously declined and did not recover in the presence of a less sensitive competing species (Daphnia magna). By contrast, in the absence of a competitor, insecticide effects on the more sensitive species were only observed at concentrations 1 order of magnitude higher, and the species recovered more rapidly after a contamination event. The underlying processes are experimentally identified and reconstructed using a simulation model. We conclude that repeated toxicant pulse of populations that are challenged with interspecific competition may result in a multigenerational culmination of low-dose effects.

Toxicological evaluation of ametryn effects in Wistar rats

“…Recently, there has been a rapid decline in biodiversity in many ecosystems and this fact has been associated to environmental stressors such as pesticides in high concentrations, suspensions, and organic pollution, which are a threat to worldwide biota (Liess et al, 2013). Our research group has demonstrated testicular toxicity in Wistar rats exposed to sub-lethal doses of ametryn (Dantas et al, 2015), highlighting oxidative stress induction and decrease of Leydig cell and sperm number, corroborating this association.…”

Effects of chemical disturbances on intertidal benthic assemblages

“…These sub-lethal effects could impair organisms in numerous ways, such as decreasing their reproduction efforts or their competitive ability (e.g. Liess et al, 2013). These could eventually lead to changes in their abundances, and consequently, to changes in community structure.…”

Scientific Opinion on good modelling practice in the context of mechanistic effect models for risk assessment of plant protection products

“…When acute effects are modelled, the maximum concentration over time may be most relevant (Liess and von der Ohe, 2005). However, culmination of sequential pulses of pesticides may need to be considered in cases where several pulses of pesticides affect individuals, cohorts or successive generations within a population (Liess et al, 2013). When simulating chronic effects and recovery, the decrease of the exposure concentration resulting from dissipation (the exposure regime) is important as well.…”