Mixture toxicity assessment of a biocidal product based on reproduction and avoidance behaviour of the collembolan Folsomia candida

Considering safe and sustainable by design alternatives-Environmental hazards of an agriculture nano-enabled pesticide to non-target species

Nanopesticides (Npes) offer improved efficacy compared to their conventional forms while reducing the usage/application rates, hence being more sustainable options. However, there is still a knowledge gap on the Npes environmental impacts. To support the safety of nano-enabled pesticides, the present study aimed at assessing the toxicity of the commercial Npe NUCOP-M and the active substance copper oxychloride, using the ecotoxicological soil model Enchytraeus crypticus and LUFA 2.2 soil. Bioassays were performed to assess various endpoints within short-to longer-term exposures: avoidance behaviour (2 d), hatching (13 d), survival, reproduction and organisms' size (based on the standard OECD test (28 d), the OECD extension (56 d), and the Full Life Cycle test - FLCt (46 d)). Based on the standard OECD test and its extension, NUCOP-M had a similar level of toxicity as copper oxychloride without indications of increase in toxicity over time (28 versus 56 d). The shorter-term exposures (2 and 13 d) showed higher toxicity for copper oxychloride. The exposure from cocoon stage (FLCt) seemed to provide an adaptative advantage (reduced toxicity) to NUCOP-M. The differences might be related to a slower release of Cu2+ ions from NUCOP-M, which seems to account for the toxicity at longer-term. Based on the recommended application doses (ca. 1.72 mg NUCOP-M kg-1, i.e. 0.62 mg Cu kg-1 in the topsoil) there is no unacceptable risk of NUCOP-M on the enchytraeid population.

Environmental hazards of WELGRO® Cu+Zn: A nano-enabled fertilizer

Nanoagrochemicals have the potential to revolutionize agriculture towards a precision farming system, able to reduce application rates and consequently their environmental footprint, while keeping efficacy. Several nanoagrochemicals (including nanopesticides (Npes) and nanofertilizers (Nfer)) are already commercialized but the environmental risk assessment of these advanced materials is often lacking. In the present study, we studied the commercial fertilizer WELGRO® Cu + Zn and assessed its ecotoxicity to the soil invertebrate species Enchytraeus crypticus (Oligochaeta), further comparing it to its individual active substances CuO and ZnO. To get a comprehensive picture of possible effects, we used four types of highly relevant tests in LUFA 2.2 soil: 1) avoidance behaviour (2 days), 2) reproduction (OECD standard, 28 d), 3) its extension (56 d), and 4) the full life cycle (FLC) (46 d) - this high level of hazard screening allows for increased interpretation. The results confirmed the nano-features of WELGRO® and a higher toxicity than the mixture of the individual components CuO + ZnO. E. crypticus avoided the soil spiked with WELGRO® and CuO + ZnO, this being the most sensitive endpoint - avoidance behaviour. Both WELGRO® and the active substances were little to non-toxic based on the OECD standard test. However, the toxicity dramatically increased in the tests focussing on longer-term sustainability measures, i.e., 56 days, ca. 170 for WELGRO®. This seems related to the nano-features of WELGRO®, e.g., slow release of ions from the nanoparticles throughout time. The FLCt results showed WELGRO® affected hatching and juveniles' survival, being these the most sensitive life stages. Hence, under actual real world field usage scenarios, i.e., based on the recommended application rates, nanoenabled WELGRO® can affect oligochaete populations like enchytraeids, both via the immediate avoidance behaviour and also via prolonged exposure periods.

Additive and dose-dependent mixture effects of Flumite 200 (flufenzin, acaricide) and Quadris (azoxystrobin, fungicide) on the reproduction and survival of Folsomia candida (Collembola)

Chemical plant protection is still a dominant agricultural practice in the world, and usually fields are treated with several pesticides many times per year. This means that not only the single substances affect the environment and the non-target organisms, but their mixtures. Our model organism was Folsomia candida (Collembola). We aimed to gain information on the toxicity of Quadris (azoxystrobin) and Flumite 200 (flufenzine aka. diflovidazine) on survival and reproduction and whether the animals can mitigate the toxicity with soil and/or food avoidance behaviour. Also, we aimed to test the effect of the mixture of these two pesticides. We used the OECD 232 reproduction test, a soil avoidance test, and a food choice test for both single pesticides and their mixture. We prepared the mixtures based on the concentration addition model, so the 50% effective concentrations (EC50) of the single materials were used as one toxic unit with a constant ratio of the two materials in the mixture. In the end, the measured mixture EC and LC (lethal concentration) values were compared to the estimate of the concentration addition model. Both materials were toxic to the Collembola in much higher concentrations than the recommended field concentrations (Flumite 200 EC50: 1.096, LC50: 1.561, Quadris EC50: 65.568, LC50: 386.165 mg kg-1). The springtails did not consistently avoid the polluted soils, this only happened in higher concentrations. The mixtures seemed to have additive effects on the reproduction and we found dose-dependent interaction with the survival (EC50: 1.022 Toxic Unit, 0.560 Flumite 200 and 33.505 Quadris; LC50: 1.509 Toxic Unit, 0.827 Flumite 200 and 49.471 mg kg-1 Quadris). The deviation from the concentration addition model suggests that the curve starts with a synergy. but above EC50 it becomes antagonistic. We conclude that both Quadris and Flumite 200 are safe for springtails until the recommended field concentration is respected. However, if higher concentrations are used the animals cannot avoid Flumite 200 and the toxic effects can fully manifest. Consequently, the dose-dependent deviation from the concentration addition model is a reason for caution as the low concentrations were synergistic for survival. That means the field concentrations can possibly cause synergistic effects. However, to clarify that further tests are necessary.

Ecotoxicological assessment of Uruguay River and affluents pre- and post-pesticides' application using Caenorhabditis elegans for biomonitoring

Uruguay River is the most important river in western Rio Grande do Sul, separating Brazil from Argentina and Uruguay. However, its pollution is of great concern due to agricultural activities in the region and the extensive use of pesticides. In a long term, this practice leads to environmental pollution, especially to the aquatic system. The objective of this study was to analyze the physicochemical characteristics, metals and pesticides levels in water samples obtained before and after the planting and pesticides' application season from three sites: Uruguay River and two minor affluents, Mezomo Dam and Salso Stream. For biomonitoring, the free-living nematode Caenorhabditis elegans was used, which were exposed for 24 h. We did not find any significant alteration in physicochemical parameters. In the pre- and post-pesticides' samples we observed a residual presence of three pesticides (tebuconazole, imazethapyr, and clomazone) and metals which levels were above the recommended (As, Hg, Fe, and Mn). Exposure to both pre- and post-pesticides' samples impaired C. elegans reproduction and post-pesticides samples reduced worms' survival rate and lifespan. PCA analysis indicated that the presence of metals and pesticides are important variables that impacted C. elegans biological endpoints. Our data demonstrates that Uruguay River and two affluents are contaminated independent whether before or after pesticides' application season. In addition, it reinforces the usefulness of biological indicators, since simple physicochemical analyses are not sufficient to attest water quality and ecological safety.

Toxicity of fungicides to terrestrial non-target fauna - Formulated products versus active ingredients (azoxystrobin, cyproconazole, prothioconazole, tebuconazole) - A case study with Enchytraeus crypticus (Oligochaeta)

Despite the high usage of pesticides in current agricultural practices, its effects to humans and to the environment (non-target species) are a continuous concern. Soil dwelling organisms are among the first in line of exposure to pesticides, however their risks are often based on the pure active ingredient (a.i.) and not on the commercial formulated products (FPs) actually applied in the fields. In the present study, we investigated the effects of two fungicide FPs versus its a.i. (s): Amistar® XTRA and the respective a.i. (s) azoxystrobin and cyproconazole, and Prosaro® 250 EC and the respective a.i. (s) prothioconazole and tebuconazole, to the non-target soil oligochaete Enchytraeus crypticus. The standard Enchytraeid Reproduction Test was used to assess effects on survival and reproduction. Results showed that Amistar was more toxic than Prosaro, particularly for reproduction (EC₅₀ = 161 mg Amistar/kg soil, EC₅₀ = 350 mg Prosaro/kg soil). For both FPs, reproductive effects were mainly related to one of its a.i. (s) (azoxystrobin [EC₅₀ = 37 mg azosxystrobin/kg soil] for Amistar, and tebuconazole [EC₅₀ = 41 mg tebuconazole/kg soil] for Prosaro), while lethal effects were not predicted by the toxicity of its a.i. (s) (particularly in the case of Prosaro, which was more toxic than its a.i. (s)). These findings highlight the need to further explore the toxicity data of the FPs compared to the a.i. (s), aiming to predict a more realistic environmental hazard of pesticides.

Effects of Amorphous Silica Nanopowders on the Avoidance Behavior of Five Soil Species-A Screening Study

Silica nanoparticles (SiO2NPs) are one of the most used in commercial products and biomedical tools, however, their environmental effects have not been fully described. Although negative effects of SiO2NPs on the behavior of freshwater invertebrates have been reported, the knowledge is limited, especially the effect of nanopowders in terrestrial organisms. Accordingly, the aim of the present study is to understand the effects of SiO2NPs on the avoidance behavior of five soil species, whose niche may differ thus contributing to differential harmful SiO2NPs effects. Hence, avoidance assays testing SiO2NPs concentrations of 0, 10, 100, 250, 500 and 1000 mg/kg were performed with Enchytraeus crypticus, Folsomia candida, Tenebrio molitor, Porcellionides pruinosus and Eisenia fetida. SiO2NPs induced different behavioral effects, depending on the invertebrate ecology/habitat, exposure route and physiology. T. molitor, P. pruinosus and F. candida did not avoid contaminated soil; however, E. crypticus and E. fetida significantly avoided SiO2NPs spiked soil. Since these terrestrial worms (oligochaetes) live mostly burrowed in the soil, this can provide greater opportunity for SiO2NPs' uptake. On the other hand, the other tested organisms mainly living on the upper part of the soil did not avoid the SiO2NPs spiked soil. The avoidance data obtained here also highlight the need for further studies to understand whether (or not) the detected behavioral responses are linked to either neurotransmission processes or sensorial aspects of the biological models.