# Combined Modeling of Multiple Exposure Routes for Terrestrial Arthropods Using the Toxicokinetic–Toxicodynamic BufferGUTS Model

## TL;DR

This paper introduces a new model to assess pesticide risks to non-target arthropods by combining multiple exposure routes into a single framework.

## Contribution

The study extends the BufferGUTS model to integrate multiple exposure routes for terrestrial arthropods without species-specific adaptations.

## Key findings

- The model was tested with honeybee data for topical and oral exposure to five insecticides.
- Three insecticides showed nonsimilar effects between topical and oral exposure routes.
- The model can help identify the most relevant exposure routes for each pesticide.

## Abstract

Pesticide applications in agricultural landscapes pose
significant
risks to nontarget arthropods (NTAs), which are vital for maintaining
ecological functions such as pollination and pest control. Effective
risk assessment is made challenging by the complexity of terrestrial
exposure, which is highly variable and event-driven. Unlike in aquatic
settings, NTAs experience pesticide exposure through multiple routes,
such as overspray, ingestion, or contact. To integrate such multiple
exposure routes into a unified framework, this study proposes an extension
to the toxicokinetic–toxicodynamic (TKTD) and time-resolved
BufferGUTS model that can be applied to a broad range of NTAs without
species-specific adaptations. Our model extension draws on principles
from mixture toxicity and allows for individual effect contributions
and effect kinetics per uptake route, providing further insight into
the substance effect dynamics. We tested the model using honeybee
() data for topical and
oral exposures to five insecticides. Among the insecticides tested,
only one exhibited different kinetics between topical and oral applications,
while three exhibited nonsimilar effects from the two routes. We recommend
the integration of such TKTD models into environmental risk assessment
practices to combine uptake route effects, model field-relevant exposure
scenarios, and identify the most relevant routes for each substance.
This will enable more informed decision-making, thereby enhancing
ecological management and protection efforts.