Immediate and mid-term effects of pyrimethanil toxicity on microalgae by simulating an episodic contamination

Review: Progress towards research on the toxicology of pyrimethanil

Pyrimethanil is a persistent environmental pollutant that poses a significant threat to human health. In this review, we summarize the fungicidal mechanism of pyrimethanil and its toxicological effects on aquatic organisms and mammals, as well as its impact on growth and development as an endocrine disruptor. Additionally, we investigate the metabolism of pyrimethanil in mammals and its molecular mechanism in the occurrence of Alzheimer's disease. Furthermore, this review outlines the influence of climate change on the toxicity of pyrimethanil, emphasizing the need to consider the impact of mixtures of multiple compounds on human health. Finally, we propose several promising future directions for pyrimethanil research, believing that there is a better understanding of the interaction between pyrimethanil and organisms, as well as the development of techniques to remove pyrimethanil, may be the best approach to eliminating the threat posed by this compound.

Effects of pyrimethanil fungicide on Chironomidae community structure

The use of agrochemicals in agriculture may impact aquatic ecosystems, particularly influencing the stream insect communities. Among aquatic insects, the family Chironomidae is the most abundant and species-diverse insect group found in freshwater ecosystems. However, in the southern hemisphere, studies with Chironomidae are still sparse, compared to Europe and North America. The present study evaluates the responses of Chironomidae species (Insecta: Diptera) to pyrimethanil fungicide in a mesocosm experiment. Water contamination and chironomid community were monitored over 10 months. After five months of monitoring, the pyrimethanil fungicide was completely degraded and there was a statistically significant increase in the Margalef Richness and Shannon-Wiener Index (H') in the control units when compared with the contaminated mesocosms (p = 0.003). Our results point out that the utilization of agrochemicals can be a harmful factor influencing negatively the Chironomidae populations. This finding has key implications for insect conservation strategies and ecological management environments.

Effects of abamectin-based and difenoconazole-based formulations and their mixtures in Daphnia magna: a multiple endpoint approach

This study evaluated the toxicity of pesticide formulations Kraft® 36 EC (active ingredient-a.i. abamectin) and Score® 250 EC (a.i. difenoconazole), and their mixtures in Daphnia magna at different biological levels of organization. Survival, reproduction and biochemical markers (cholinesterase (ChE), catalase (CAT) and lipid peroxidation (LPO)) were some of the endpoints evaluated. Total proteins and lipids were also studied together with energy consumption (Ec). D. magna neonates were exposed for 96 h to Kraft (2, 4, and 6 ng a.i./L) and Score (12.5, 25, and 50 µg a.i./L) for the biochemical experiments, and for 15 days to abamectin (1-5 ng a.i./L) and to difenoconazole (3.12-50 µg a.i./L) to assess possible changes in reproduction. Exposures of organisms to both single compounds did not cause effects to antioxidant and detoxifying enzymes, except for LPO occurring at the highest concentration of difenoconazole tested. For ChE and CAT there was enzymatic induction in mixture treatments organisms, occurring at minor pesticides concentrations for CAT and at the two highest concentrations for ChE. There were no significant differences for total protein in D. magna but lipids showed an increase at the highest concentrations of pesticide mixture combinations. There was a significant increase of Ec in individuals of all treatments tested. In the chronic test, increased fecundity occurred for D. magna under difenoconazole exposures and mixtures. This study demonstrated that mixtures of these pesticides caused greater toxicity to D. magna than when tested individually, except for Ec. Therefore, effects of mixtures are very hard to predict only based on information from single compounds, which most possibly is the result of biological complexity and redundancy in response pathways, which need further experimentation to become better known.

Long-term effects of the fungicide pyrimethanil on aquatic primary producers in macrophyte-dominated outdoor mesocosms in two European ecoregions

Even though empirical data supporting sound ecoregion-specific ecotoxicological evaluations are still scarce, the differences of environmental (including climatic) conditions in specific ecoregions are already currently being regulated for environmental risk assessment of pesticides in Europe. To shed new light on the ecotoxicological effects of pesticides on aquatic communities across ecoregions, the model pollutant pyrimethanil (fungicide) was tested in an outdoor mesocosm study with macrophyte-dominated communities in the European "South" (Portugal) and "Centre" (Germany) regulatory zones. Phytoplankton indicators monitored over 12 months indicated a low risk of the fungicide (0.73 or 0.77 mg pyrimethanil L^-1, single application) to phytoplankton functioning; as expected since exposure simulated worst-case scenarios. However, the growth of key structural macroalgae and macrophytes was affected by the fungicide and negative effects occurred, especially in the Central zone experiment. Such effects were not detected earlier than approximately nine months post single pyrimethanil application. The presence or absence of such extremely long-lasting/delayed pyrimethanil effects depended on species, competitive situation, and ecoregion-specific physico-chemical environment. The present findings suggest that a better understanding of both direct and indirect effects of fungicide pollution on aquatic flora in two European ecoregions helps to consolidate the environmental risk assessment of pesticides in specific regulatory zones.

Effects of long-term exposure to two fungicides, pyrimethanil and tebuconazole, on survival and life history traits of Italian tree frog (Hyla intermedia)

Over the last few years, the hazards associated with the extensive use of fungicides have become an issue of great concern but, at present, the effects of these substances on amphibians remain poorly understood. The goal of the present study was to assess the effects of two commonly used fungicides, tebuconazole and pyrimethanil, on Italian Tree Frog (Hyla intermedia), a species frequently found in agricultural areas. Tadpoles were exposed to fungicides from developmental Gosner stage 25 (GS 25) to completion of metamorphosis (GS 46) and the whole exposure period lasted 78 days. For both tested fungicides we used two concentrations (5 and 50μg/L) that are comparable to those detected in surface waters, near agricultural fields. A variety of sublethal effects-on growth, development, behavior, and physiology-may be used for evaluating alterations induced by pollutants in amphibians. We estimated whether pyrimethanil and tebuconazole exposure impacted on H. intermedia life history traits. For this purpose, survival, growth, development, initiation of metamorphosis, success and size at metamorphosis, time to metamorphosis, and frequency of morphological abnormalities were evaluated. We showed, for all considered endpoints, that the exposure to tebuconazole exerts more harmful effects on H. intermedia than does exposure to pyrimethanil. Before the onset of metamorphic climax we showed, for both fungicides, that the low concentrations (5μg/L) induced significantly greater effects than the higher ones (50μg/L) on survival and deformity incidence. During the metamorphic climax, a complete reversal of this nonlinear trend takes place, and the percentage of animals initiating metamorphosis was reduced in fungicide-exposed groups in a concentration-dependent manner. Furthermore, a strong correlation emerged between fungicide exposure and the incidence of morphological abnormalities such as tail malformations, scoliosis, edema, mouth and limb deformities. Exposure to tested fungicides also caused a reduction in developmental rates just prior to the onset of metamorphic climax, which translated to a significant delay in timing of metamorphosis. We detected a drastic decrease in the success at metamorphosis in all exposed groups, compared to control group (86.25%). In fact, the percentage of survived larvae to GS 46, in the high and low concentrations, respectively, was only 22.5% and 36.25% in tebuconazole-exposed groups and 43.75% (50μg/L) and 56.25% (5μg/L) in pyrimethanil-exposed groups. Our findings underscore the hazardous properties of these two fungicides for non-target species in the context of ecotoxicological risk assessment. No published studies have addressed the long-term effects of tebuconazole and pyrimethanil on amphibians. To date, this is one of only a few studies documenting the effects of fungicide exposure over the whole larval development.