Pesticides in aquifers from Latin America and the Caribbean

Occurrence and environmental risk assessment of pesticides reveal important threats to aquatic organisms in precordilleran rivers of north-central Chile

While pesticides are essential for food production, their widespread use poses environmental risks beyond lowland areas. Recent evidence indicates that mountain ecosystems are also vulnerable due to both local agriculture and long-range atmospheric transport. This study assesses pesticide contamination and ecological risks in five mountainous agricultural watersheds of north-central Chile, where pesticides support intensive crop production. Using primarily polar organic chemical integrative samplers (POCIS), complemented by sediment samples, we found pesticides at 26 of 30 sampled sites. Detection varied by location and method. Desethylatrazine, an atrazine metabolite, was most frequently found in POCIS samples, detected at 20 sites across all watersheds. While other pesticides only occurred at few sites, their presence across multiple, geographically dispersed locations contributed to extensive ecological risk. Northern watersheds (Limarí, Choapa, Aconcagua) showed the highest ecological risks, despite lower pesticide loads, due to the presence of highly toxic insecticides. Key factors influencing pesticide distribution included water conductivity, agricultural land use, and latitude. Ecotoxicological risk assessments revealed eight pesticides exceeding high-risk thresholds for aquatic organisms-mainly insecticides and fungicides. Pyrethroids such as deltamethrin, cyfluthrin, and lambda-cyhalothrin posed severe threats to fish and invertebrates. High-risk levels were also detected in sediments, particularly in the northernmost Limarí watershed. These findings underscore the urgent need for targeted monitoring and stricter pesticide regulation in mountain freshwater ecosystems of Chile, which are vital water sources and harbor unique biodiversity. This study provides one of the first comprehensive evaluations of pesticide risks in mountainous rivers, highlighting the ecological threats from agricultural contaminants.

Population genomics of Anopheles darlingi, the principal South American malaria vector mosquito

Malaria in South America remains a serious public health problem. Anopheles (Nyssorhynchus) darlingi is the most important malaria vector across tropical Latin America. Vector-targeted disease control efforts require a thorough understanding of mosquito demographic and evolutionary patterns. We present and analyze whole genomes of 1094 A. darlingi (median depth 18x) from six South American countries. We observe deep geographic population structure, high genetic diversity including thirteen putative segregating inversions, and no evidence for cryptic sympatric taxa despite high interpopulation divergence. Strong signals of selection are plausibly driven by insecticides, especially on cytochrome P450 genes, one of which we validated experimentally. Our results will facilitate effective mosquito surveillance and control, while highlighting ongoing challenges that a diverse vector poses for malaria elimination in the western hemisphere.

Uptake and translocation of pesticides in pepper and tomato plants

BACKGROUND

In this study, field and greenhouse experiments were done with spray application of the insecticides acetamiprid, indoxacarb, deltamethrin, λ-cyhalothrin, spinosad, chlorantraniliprole on pepper and tomato plants. Results were interpreted with numerical modeling.

RESULTS

Observed fruit concentration dynamics could be described overall well by modeling. After application, concentrations decreased in pepper and (slower) in tomato fruits (lower degradation and dissipation for tomato). Chemical input to individual above-ground compartments (fruit, leaf, stem, soil), arising from spray, was among the unknowns and hence estimated. Input to fruits was estimated 1-13% and 1-17% of the total applied amount; input to stem, leaf and/or soil 0-13% and 0-26% (pepper and tomato). Input showed high variation across compounds, with considerable uncertainty due to a partly low sensitivity of stem/leaf/soil input to fruit concentrations. The pathway stem-fruit was relevant for all compounds except λ-cyhalothrin (pepper, tomato) and deltamethrin (tomato). The pathways soil-root-stem-fruit and leaf-stem-fruit (phloem) were only sensitive for acetamiprid and chlorantraniliprole.

CONCLUSION

The dynamic model approach, implementing the appearance and growth of individual fruits, was after calibration successful in describing insecticide fate in pepper and tomato plants. Special consideration was given to dynamic modelling of plant growth and connected xylem and phloem flow. The dynamic approach was superior to assuming constant plant mass and transpiration, where growth dilution is described by rate constants. Information on the time-window of experiments within the vegetation period and on the number and appearance of individual fruits is important for adequately describing growth and thus chemical fate within plants. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Mutagenic drinking water and different levels of emerging micropollutants in Southern Brazil: A new challenge

This study investigated the presence of mutagenic compounds in raw and treated waters at four water treatment plants (WTP01 to WTP04), in southern Brazil. Samples were concentrated using Amberlite XAD4 resin and the acidic and neutral pH fractions tested by mutagenesis in Salmonella/microsome assay, using TA98, TA100 and YG7108 strains in presence and absence of metabolic activation (in vitro human S9). Mutagenesis in raw water was found only by strain TA98 at WTP03, with and without S9. In treated water, significant results were found for TA98 and TA100 strains, the latter being the most sensitive, with prevalence in acidic extract tests without S9. A chemical analysis was performed in the water samples, prioritizing the investigation of the presence and concentration of globally used Emerging Micropollutants (EMs). These compounds in water sources have the potential to contaminate drinking water due to the inefficiency of the conventional treatment employed and can generate disinfection by-products. WTP04 site had the highest total EMs in raw and treated waters, followed by WTP03 in treated water. These WTPs expressed an EMs removal capacity of 45% and only 23%, respectively. Some pharmaceuticals and caffeine showed the highest concentrations, and the latter was directly related to the disposal of domestic sewage in the aquatic ecosystem. The presence of EMs in water after treatment for all WTPs investigated suggests the importance of expanding guidelines that include EMs to establish better standards for the protection of aquatic life and better quality of the drinking water supplies.

Acute toxicity effects of pesticides on beneficial organisms - Dispelling myths for a more sustainable use of chemicals in agricultural environments

Agricultural practitioners, researchers and policymakers are increasingly advocating for integrated pest management (IPM) to reduce pesticide use while preserving crop productivity and profitability. Using selective pesticides, putatively designed to act on pests while minimising impacts on off-target organisms, is one such option - yet evidence of whether these chemicals control pests without adversely affecting natural enemies and other beneficial species (henceforth beneficials) remains scarce. At present, the selection of pesticides compatible with IPM often considers a single (or a limited number of) widely distributed beneficial species, without considering undesired effects on co-occurring beneficials. In this study, we conducted standardised laboratory bioassays to assess the acute toxicity effects of 20 chemicals on 15 beneficial species at multiple exposure timepoints, with the specific aims to: (1) identify common and diverging patterns in acute toxicity responses of tested beneficials; (2) determine if the effect of pesticides on beetles, wasps and mites is consistent across species within these groups; and (3) assess the impact of mortality assessment timepoints on International Organisation for Biological Control (IOBC) toxicity classifications. Our work demonstrates that in most cases, chemical toxicities cannot be generalised across a range of beneficial insects and mites providing biological control, a finding that was found even when comparing impacts among closely related species of beetles, wasps and mites. Additionally, we show that toxicity impacts increase with exposure length, pointing to limitations of IOBC protocols. This work challenges the notion that chemical toxicities can be adequately tested on a limited number of 'representative' species; instead, it highlights the need for careful consideration and testing on a range of regionally and seasonally relevant beneficial species.

Effects of herbicides and fertilization on biofilms of Pampean lotic systems: A microcosm study

We experimentally assessed the impact of the application of herbicides and fertilizers derived from agricultural activity through the individual and simultaneous addition of glyphosate, atrazine, and nutrients (nitrogen 'N' and phosphorus 'P') on the biofilm community and their resilience when the experimental factors were removed. We hypothesize that i) the presence of agrochemicals negatively affects the biofilm community leading to the simplification of the community structure; ii) the individual or simultaneous addition of herbicides and nutrients produces differential responses in the biofilm; and iii) the degree of biofilm recovery differs according to the treatment applied. Environmentally relevant concentrations of glyphosate (0.7 mgL-1), atrazine (44 μgL-1), phosphorus (1 mg P L-1 [KH2PO4]), and nitrogen (3 mg N L-1[NaNO3]) were used. Chlorophyll a, ash-free dry weight, abundance of main biofilm groups and nutrient contents in biofilm were analyzed. At initial exposure time, all treatments were dominated by Cyanobacteria; through the exposure period, it was observed a progressive replacement by Bacillariophyceae. This replacement occurred on day 3 for the control and was differentially delayed in all herbicides and/or nutrient treatments in which the abundance of cyanobacteria remains significant yet in T5. A significant correlation was observed between the abundance of cyanobacteria and the concentration of atrazine, suggesting that this group is less sensitive than diatoms. The presence of agrochemicals exerted differential effects on the different algal groups. Herbicides contributed to phosphorus and nitrogen inputs. The most frequently observed interactions between experimental factors (nutrients and herbicides) was additivity excepting for species richness (antagonistic effect). In the final recovery time, no significant differences were found between the treatments and the control in most of the evaluated parameters, evincing the resilience of the community.

Pesticides in soil, groundwater and food in Latin America as part of one health

We here report of a conference about "Pesticides in Soil, Groundwater and Food in Latin America as part of One Health" that took place at the "IV Seminario Internacional de Sanidad Agropecuaria (SISA)" in Varadero, Cuba, 8-12 May 2023. Researchers of Latin America (Argentina, Brazil, Chile, Costa Rica, Colombia, Cuba, Mexico) and Switzerland (workshop initiator) held presentations about occurrence and effects of pesticides on the environment, human health, the replacement of highly hazardous pesticides (HHP) by agroecological alternatives and the agri-food value chain. In a subsequent round table discussion, the presenters identified deficits, needs, interests and opportunities. According to them, the lack of awareness of pesticide use affects the health and safety of workers applying the chemicals. Despite Latin America representing the main agricultural area in the world with a very intense pesticide use, monitoring data of pesticides in soil, surface and groundwaters, food, as well as in humans are missing. Risks of pesticides to humans should be assessed so that authorities can withdraw or limit within "short time" the access to corresponding formulations on the market. Also, communication is not state of the art and should be improved as, e.g. the teaching of workers and farmers, how to correctly use and apply pesticides or the briefing of decision makers. Pollinators suffer from multiple stressors not the least due to pesticides, and alternatives are badly needed. On the technical side, the different analytical methods to determine residues of active ingredients and transformation products in matrices of concern should be harmonized among laboratories.Seven future actions and goals were identified to overcome the above deficits. Next steps after the publishing of this conference report are to harmonize and complete the information status of the presenters by exchanging the results/data already present. Therefore, a platform of interaction to address issues described above and to enhance collaboration shall be created. Samples of different matrices shall be exchanged to harmonize the chemical analysis and establish interlaboratory comparisons. Such activities might be facilitated by joining international associations or organizations, where researchers can offer their expertise, or by forming a new pesticide network for Central and South America that could present tailored projects to national and international organizations and funding agencies.

ATR induces hepatic lipid metabolism disorder in rats by activating IRE1α/XBP1 signaling pathway

Atrazine (ATR) is a widely used herbicide and due to its persistence in environment and bioaccumulation, it can cause harmful impacts on human health. ATR exposure can lead to disorders of lipid metabolism in the liver, but its underlying mechanism is still unclear. 40 eight-week-old rats were given different doses of ATR (0, 0.5, 5 and 50 mg/kg/d) for 90 days. The liver tissue and serum were collected for histological observation and biochemical analysis. The levels of lipid and oxidative stress were assessed using colorimetry. Changes in MMP and ROS of liver cells were observed through flow cytometry. The expression of mRNA and protein was detected using Real-Time PCR and western blot. The results showed that TC and HDL-C levels in both the liver and serum were increased in the ATR-treated groups. The levels of MDA were accumulated, while the levels of SOD and GSH were depleted in the liver with ATR exposure. The expression of liver lipid metabolism related genes (SCD1, DGAT2, ACC1, PPARγ) was elevated. The liver ERS was activated and the gene expression of IRE1α/XBP1 signal pathway and GRP78, GRP94 in the liver was increased. There was a correlation between the levels of ERS and the levels of lipid metabolism. These results suggested that ATR can activate ERS and promote the expression of IRE1α/XBP1 signaling pathway, and further lead to lipid metabolism disorders in rat liver. This study can provide valuable insights as a reference for the prevention and control of hazards associated with agricultural residues.