Challenges and ways forward in pesticide emission and toxicity characterization modeling for tropical conditions

Abstract

Purpose In tropical cropping systems, pesticides are extensively used to fight pests and ensure high crop yields. However, pesticide use also leads to environmental and health impacts. While pesticide emissions and impacts are influenced by farm management practices and environmental conditions, available Life Cycle Inventory (LCI) emission models and Life Cycle Impact Assessment (LCIA) toxicity characterization models are generally designed based on temperate conditions. There is, hence, a need for adapting LCI and LCIA models for evaluating pesticides under tropical conditions. To address this need, we aim to identify the characteristics that determine pesticide emissions and related impacts under tropical conditions, and to assess to what extent LCI and LCIA models need to be adapted to better account for these conditions. Methods We investigated the state-of-knowledge with respect to characteristics that drive pesticide emission patterns, environmental fate, human and ecological exposures, and toxicological effects under tropical conditions. We then discuss the applicability of existing LCI and LCIA models to tropical regions as input for deriving specific recommendations for future modeling refinements. Results and discussion Our results indicate that many pesticide-related environmental processes, such as degradation and volatilization, show higher kinetic rates under tropical conditions mainly due to higher temperatures, sunlight radiation, and microbial activity. Heavy and frequent rainfalls enhance leaching and runoff. Specific soil characteristics (e.g., low pH), crops, and cropping systems (e.g., mulching) are important drivers of distinct pesticide emission patterns under tropical conditions. Adapting LCI models to tropical conditions implies incorporating specific features of tropical cropping systems (e.g., intercropping, ground cover management), specific drift curves for tropical pesticide application techniques, and better addressing leaching processes. The validity domain of the discussed LCI and LCIA models could be systematically extended to tropical regions by considering tropical soil types, climate conditions, and crops, and adding active substances applied specifically under tropical conditions, including the consideration of late applications of pesticides before harvest and their effect on crop residues and subsequent human intake. Conclusions Current LCI and LCIA models are not fully suitable for evaluating pesticide emissions and impacts for crops cultivated in tropical regions. Models should be adapted and parameterized to better account for various characteristics influencing emission and impact patterns under tropical conditions using best available data and knowledge. Further research is urgently required to improve our knowledge and data with respect to understanding and evaluating pesticide emission and impact processes under tropical conditions.

Exposure and toxicity characterization of chemical emissions and chemicals in products: global recommendations and implementation in USEtox

“…Further refinement of these initial recommendations, along with alignment with efforts to update ecotoxicity impact assessment (Fantke et al 2018a;Owsianiak et al 2019), led to a set of final recommendations discussed and agreed upon in a scientific expert workshop held in Valencia (Spain) in 2018. While the general recommendations have been summarized in the related workshop report (Frischknecht & Jolliet 2019), the present paper details the underlying methodological framework for human near-field exposure and toxicity characterization.…”

Improved plant bioconcentration modeling of pesticides: The role of periderm dynamics

“…Second, the weather and soil conditions are not considered in our model and may differ from those in the experimental study, which could significantly affect the fate of pesticides in soil and further impact the uptake of pesticides by potatoes. Weather conditions such as temperature and humidity in the soil and air can affect the transpiration rate of plants, which determines the pesticide uptake rate by plants 3,37,59–61 . Moreover, different geographical regions always form different soil characteristics, including mineral contents, microorganisms, and physical properties, which can affect the horizontal or vertical distribution of pesticide residues in soil 62,63 .…”

“…The entire transport process is modeled based on three compartments: (i) the soil compartment where pesticide transport is predominantly affected by pesticide emission, degradation in soil, and diffusion to (or from) potato tubers; (ii) the tuber periderm compartment, where pesticide transport is determined by diffusion to (or from) both the soil and medulla, dilution by growth of the potato, and degradation; and (iii) the medulla compartment, where pesticide transport is also determined by diffusion, growth dilution, and degradation processes. Other possible pesticide fate processes, such as volatilization from soil surfaces to air and leaching to deeper soil layers, which are affected by weather and soil conditions, 37 are not discussed in more detail due to our focus on the influence of the potato periderm on pesticide residue dynamics in edible potato tubers. When incorporating processes between soil, potato periderm, and medullar into more complex plant uptake frameworks, additional relevant processes are usually already considered.…”

No simple menu for sustainable food production and consumption

“…As the crop production systems and pesticide application regimes in tropical climates are quite different from those in temperate climates, the modeling of the impact of pesticides on human and environmental health developed mainly based on temperate conditions needs to be adjusted accordingly. The key factors to be taken into account are the environmental characteristics of the tropical conditions along with agricultural practices and farmers' behavior (Gentil et al 2019). To accommodate this, the existing databases need to be extended to include tropical crop characteristics and cropping/farm management practices as well as soil and climate types.…”