Chemical and (eco)toxicological characteristics of pyrimethanil .
Via the application of agrochemicals, farmers currently guarantee high productivity of fruit and vegetable crops. However, pest reduction using excessive amounts of such chemicals has a negative effect on aquatic organisms. The spray-drift, leaching, run-off or accidental spills occurring during or after application has become a serious and increasing problem for aquatic ecosystems. Pyrimethanil (PYR) is one of the most used fungicides. Such increase has heightened the interest in studying the potential risk and influence of PYR on the environment. In this chapter information on the PYR environmental risks for aquatic organisms was divided into three different approaches: (i) assessment of toxic effects of the pure active ingredient or the commercial formulation on primary producers, (ii) assessment of toxic effects of the pure active ingredient and PYR formulation on aquatic animals, and (iii) estimation of the role of PYR as an environmental disturber by triggering avoidance response. The available data provide evidences that PYR is potentially toxic for many aquatic species, affecting survival, reproduction, feeding, growth, and that it can disturb the environmental quality with no direct effect at the individual level by inducing organisms to migrate to less impacted areas.
- aquatic organisms
- environmental disturbance
Increasing food requirements exert a constant pressure for intensifying agricultural activities, recognized, nowadays, as one of the most important economic activities in many high and low income countries . In fact, agriculture has been considered a feasible solution for reducing the levels of poverty and hunger given that the vast majority of poor people in developing countries are concentrated in rural areas . The high demand for agricultural products requires optimizing the production to reduce the loss due to crop diseases such as those caused by fungi. Although incentives for agriculture optimization and development are usually paralleled by sustainable practices, intensive agricultural practices and the pursuit for more profitable productions have unfortunately escalated the increase in the use of agrochemicals against crop pests/pathogens. Additionally, the agrochemical market represents an important economic sector for many countries . According to the previously mentioned authors, although the use of chemicals such as lime sulfur and Bordeaux mixture as fungicides began in the mid-1800s, only in the 1960s did fungicides with specific (systemic) modes of action become protagonists in controlling against fungal pathogens. The more serious consequence is the fact that the impact of agrochemicals is not only on pests and pathogens, but also on non-target organisms inhabiting adjacent areas, including humans. The excessive and indiscriminate application of agrochemicals linked to a lack of legal control about their use, commercialization and regularization in many countries has given agrochemicals a primary role of concern in environmental management. Among the groups of chemicals used in agriculture against pathogens, fungicides are the third most used agrochemical group, representing ca. 23% of sales on the agrochemical market . Contrary to most agrochemicals, fungicides are frequently applied in a prophylactic manner several times per season, although at lower application rates than most herbicides and insecticides, which increases the risk of chronic exposure to aquatic biota . On the other hand, some organisms can develop resistance to fungicides after relatively short periods (years) of exposure, resulting in fungal pathogens being responsible for important economic losses of fruit and vegetable products [5, 6].
Via the application of agrochemicals, farmers currently guarantee high productivity of fruit and vegetable crops. However, reduction of crop losses by using excessive amounts of such chemicals has a negative effect on aquatic organisms. The spray-drift, leaching, run-off or accidental spills occurring during or after application of agrochemicals has become a serious and increasing worldwide problem for aquatic ecosystems [7, 8]. Pyrimethanil (PYR) is one of the most used fungicides that has been detected in many aquatic ecosystems  and one of the most frequently used in European vineyards [9, 10, 11]. Such increase has heightened the interest in studying the potential risk and influence of PYR on the environment [3, 5, 12–14].
The main objective of this chapter is to provide information on the environmental risks posed by PYR for aquatic organisms. For this, PYR chemical characteristics as well as its potential risk for the aquatic environment will firstly be provided and subsequently three different approaches will be discussed: (i) assessment of toxic effects of the pure active ingredient or the commercial formulation on primary producers using traditional assays with forced exposure, (ii) assessment of toxic effects of the pure active ingredient and PYR formulation on aquatic animals using traditional assays with forced exposure and
2. Pyrimethanil: Characteristics and hazard potential
The fungicide PYR (
The regulatory decision to approve a given agrochemical should be based not only on its efficiency in controlling the pest/pathogen, but also on the potential environmental impact on non-target organisms inhabiting both target and nearby areas. Given the lack of information on PYR biological effects and the imminent need to expand the range of toxicity tests, a series of recent studies have been conducted to fill in this information gap. This chapter is to present these results and integrate them with the information that was already available. With the latter purpose, different aquatic organisms from different levels of biological organization have been used in ecotoxicological studies in the past years to evaluate the potential risks due to exposure to PYR via different routes. Beside traditional toxicity tests, approaches taking into account multigeneration responses, temperature influence and behavioral endpoints as well as
3. Toxicity of pyrimethanil to primary producers (microalgae and macrophytes)
Agrochemicals can considerably affect the structure of algal communities generating functional changes, due to alterations in biotic interactions. Freshwater macrophytes and microalgae usually are not the target of agrochemicals; however, the potential impact that these compounds can have on primary producers is well known . Various studies alerting to the risk of excessive excessive pesticide application and consequent pollution of aquatic environments have been performed using different microalgae, duckweeds, and the aquatic plant
The growth of the floating plants
Also, toxicity tests with water from PYR-treated mesocosms (commercial formulation Mythos®; initial PYR concentration of 1.4 mg L-1) were performed with the microalgae
4. Toxicity of pyrimethanil to aquatic animals
The toxic effects of pure PYR on different aquatic animals and responses have also been addressed. For the cladocera
Regarding aquatic insects, the NOEC of pure PYR for the non-biting midge
Recently, impairment in the feeding ability of the tropical cladoceran
Aiming to assess the suitability of the yeast
A multi-parameter approach to assess the toxicity of PYR in a probable global change scenario has been used by Müller et al. , Seeland et al.  and Scherer et al. , based on the assumption that under climate change conditions warmer and more humid environments are expected, leading to conditions suitable for fungi development, thus an increase in the use of fungicide . Therefore, these authors evaluated if the toxicity of PYR for invertebrate species (
5. Role of pyrimethanil as environmental disturber: Avoidance assays
It has been hypothesized that contaminants can act as toxicants as well as habitat disruptors. The former role is characterized by directly measuring acute or chronic responses in organisms, while their role as habitat disruptor is directly linked to effects on habitats, reducing their quality and triggering avoidance before toxic effects are detected. The latter effect is particularly important given that concentrations at which it might occur could be considered non-risky as no toxic effect at the individual level would be usually observed [43, 44]. Habitat disturbance caused by contamination as a result of agricultural activities may, therefore, be considered an additional factor that increases the threat of local population decline [26, 45].
Given the above, a new approach based on avoidance as an endpoint and using a non-forced exposure system has been proposed to assess the role of contaminants as environmental disturbers. This approach considers that contaminants as environmental disturbers can change the community structure with no direct toxic effect on organisms as they may be able to detect and avoid contaminants [26, 43–45]. The exposure system used here creates a contamination gradient in which organisms can freely move across different levels of contamination and choose the less contaminated zone. A few studies have tested this methodology and proved that contamination levels lower than those considered potentially dangerous for organisms can trigger avoidance response by many aquatic organisms [26, 43, 44]. As a consequence, an ecosystem can suffer structural changes as individuals able to detect contamination move towards less contaminated zones [44–46].
Avoidance tests in non-forced exposure systems (Figure 3) in which a PYR gradient was simulated have been performed with fries of
According to these findings, we emphasize the importance of taking into account the risk of the presence of plant protection products in the environment, even at non-lethal concentrations, due to their potential to trigger emigration. The presence of PYR can be a decisive factor in the habitat selection process of many species, such as shown in Figure 3. The disturbing effect of contaminants on ecosystems can be comparable to the loss and fragmentation of habitats [47, 48]. Habitats with reduced quality due to presence of contaminants probably may support a smaller population as well as lose the capacity to serve as sink habitats for surrounding populations . Since avoidance experiments can provide information about contamination-driven habitat selection, the use of non-forced exposure systems is therefore encouraged in environmental risk assessment with agrochemicals.
6. Final remarks
Undoubtedly, agrochemicals are potentially dangerous for aquatic organisms. The PYR concentration causing 50% reduced offspring in the most vulnerable aquatic species
The similarly PYR-sensitive diatom
The available information provides evidences that PYR is potentially toxic for many aquatic species, affecting survival, reproduction, feeding, growth, and that it can disturb the environmental quality with no direct effect at the individual level by inducing organisms to migrate to less impacted areas. Although the amount of relevant information on the toxic potential of PYR on several species is increasing, little information is available on how the presence of PYR (and “inert compounds”) can disturb broader environmental processes: chemical balance, direct effects on primary producers and consumers, changes in structure and functioning of the community and alterations in dispersion patterns. Further studies on the probable risk due to spray-drift, leaching, run-off, or accidental spills have to be encouraged. Presently, outdoor mesocosm studies taking into account different species, endpoints and exposure types in a more complex and relevant approach by using mesocosm experiments are ongoing. Given that the behavior and effects of PYR could vary between different climate conditions, the latter experiments are being performed across different climatic regions, from tropical to South- and North-temperate. Under these three environments, chemical dynamics of PYR in water and sediment are being followed for at least a 1 year period together with the monitoring of the complex local community, individual sub-lethal effects, changes in biodiversity and implications in ecological succession. The compilation of that information could help to understand the possible role that PYR plays environmental disturber for aquatic biota.
CVM Araújo and C Shinn are grateful to FCT (Fundação para a Ciência e a Tecnologia, Portugal) for postdoctoral fellowships (reference SFRH/BPD/74044/2010 and SFRH/BPD/78642/2011, respectively) and PROMETEO program (SENESCYT – Secretaría Nacional de Educación Superior, Ciencia, Tecnología e Innovación, Ecuador), R. Müller to Hesse’s Ministry of Higher Education, Research, and the Arts (Germany) for funding by the LOEWE program (Landes-Offensive zur Entwicklung Wissenschaftlich Ökonomischer Exzellenz), and all to the FAPESP (São Paulo Research Foundation, Brazil, #11/07218-6).