MSc in Environmental Biology (1980, Universidad Autonoma de Madrid, Spain) PhD in Ecology (1985, Universidad Autonoma de Madrid, Spain) Dip Applied Science (1989, UNSW, Australia) Researcher at the UNSW and the University of Sydney (Australia) between 1992-2001 Assistant Professor at the Laboratories of Toxicology and Applied Entomology & Zoology of the Faculty of Horticulture, Chiba University (Japan), 2002-2006 Research Associate, University of Technology-Sydney (Australia), 2007-current Main interests in ecotoxicology of agrochemicals and other pollutants, their impact on populations and ecosystems, risk assessment and remediation.
Abstract: Ecotoxicology is a multidisciplinary science that examines the effects of toxic chemicals on individual organisms, populations, communities and ecosystems. However, with a 40-year history, ecotoxicology is still in its infancy. Up until recently a lot of work has been done to describe the fate and effect of chemicals in the environment, but most of it has been performed in the laboratory, usually with a narrow suite of test organisms. However, over the last two decades more and more experiments and monitoring have been performed in man-made (so called microcosms and mesocosms) as well as natural aquatic and terrestrial ecosystems. Also the use of modelling has allowed us to predict the behaviour of chemicals and their consequent effects in the environment. Impacts of pollutants at an ecosystem level, however, are reported mostly in the specialized journal literature as scattered pieces of a larger puzzle. To date, no systematic work bringing all the information on this subject together is available, neither to researchers nor the general public. This book was conceived to fill this gap.
Ecological Impacts of Toxic Chemicals presents a comprehensive, yet readable account of the known disturbances caused by all kinds of toxic chemicals on both aquatic and terrestrial ecosystems. Topics cover the sources of toxicants, their fate and distribution through the planet, their impacts on specific ecosystems, and their remediation by natural systems. Each chapter is written by well-known specialists in those areas, for the general public, students, and even scientists from outside this field. The book intends to raise awareness of the dangers of chemical pollution in a world dominated by industry and globalization of resources. Because the problems are widespread and far reaching, it is hoped that confronting the facts may prompt better management practices at industrial, agricultural and all levels of management, from local to governmental, so as to reduce the negative impacts of chemical contaminants in our Earth.
The editors would like to thank Bentham Science Publishers for providing this opportunity to bring this science to the general public.
Francisco Sánchez-Bayo,
Paul J. van den Brink,
Reinier M. Mann,
Editors
Abstract: Differences in susceptibility of five cladocerans to the neonicotinoid imidacloprid and the phenyl-pyrazole fipronil, which have been dominantly used in rice fields of Japan in recent years, were examined based on short-term (48-h), semi-static acute immobilization exposure tests. Additionally, we compared the species sensitivity distribution (SSD) patterns of both insecticides between two sets of species: the five tested cladocerans and all other aquatic organisms tested so far, using data from the ECOTOX database of U.S. Environmental Protection Agency (USEPA). The sensitivity of the test species to either imidacloprid or fipronil was consistent, spanning similar orders of magnitude (100 times). At the genus level, sensitivities to both insecticides were in the following descending order: Ceriodaphnia > Moina > Daphnia. A positive relationship was found between body lengths of each species and the acute toxicity (EC50) of the insecticides, in particular fipronil. Differences in SSD patterns of imidacloprid were found between the species groups compared, indicating that test cladocerans are much less susceptible than other aquatic species including amphibians, crustaceans, fish, insects, mollusks and worms. However, the SSD patterns for fipronil indicate no difference in sensitivity between cladocerans tested and other aquatic organisms despite the greater exposure, which overestimates the results, of our semi-static tests. From these results, Ceriodaphnia sp. should be considered as more sensitive bioindicators (instead of the standard Daphnia magna) for ecotoxicological assessments of aquatic ecosystems. In addition, we propose that ecotoxicity data associated with differences in susceptibility among species should be investigated whenever pesticides have different physicochemical properties and mode of action.
Abstract: Assessment of ecological impacts of toxicants relies currently on extrapolation of effects observed at organismal or population levels. The uncertainty inherent to such extrapolations, together with the impossibility of predicting ecological effects of chemical mixtures, can only be resolved by adopting approaches that consider toxicological endpoints at a community or ecological level. Experimental data from micro- and mesocosms provide estimates of community effect levels, which can then be used to confirm or correct the extrapolations from theoretical methods such as species sensitivity distributions (SSDs) or others. When assessing impacts, the choice of sensitive community endpoints is important. Four community endpoints (species richness, abundance, diversity and similarity indices) were evaluated in their ability to assess impacts of two insecticides, imidacloprid and etofenprox, and their mixture on aquatic and benthic communities from artificial rice paddies. Proportional changes of each community endpoint were expressed by ratios between their values in the treatment and control paddies. Regression lines fitted to the endpoint ratios against the time series of chemical concentrations were used to predict percentile impacts in the communities. The abundance endpoint appears to be the most sensitive indicator of the communities’ response, but the Czekanowski similarity index described best the structural changes that occur in all communities. Aquatic arthropods were more sensitive to the mixture of both insecticides than zooplankton and benthic communities. Estimated protective levels for 95% of aquatic species exposed to imidacloprid (<0.01–1.0 μg l−1) were slightly lower than predicted by SSD, whereas for etofenprox the protective concentrations in water (<0.01–0.58 μg l−1) were an order of magnitude lower than SSD’s predictions.
Abstract: The environmental risks of pesticides are typ- ically determined by laboratory single-species tests based on OECD test guidelines, even if biodiversity should also be taken into consideration. To evaluate how realistic these assessments are, ecological changes caused by the systemic insecticides imidacloprid and fipronil, which have different physicochemical properties, when applied at recommended commercial rates on rice fields were monitored using experimental paddy mesocosms. A total of 178 species were observed. There were no significant differences in abundance of crop arthropods among the experimental paddies. However, zooplankton, benthic and neuston communities in imidacloprid-treated field had significantly less abundance of species than control and fipronil fields. Significant differences in abundance of nekton community were also found between both insecticide-treated paddies and control. Influences on the growth of medaka fish were also found in both adults and their fries. Both Principal Response Curve analysis (PRC) and Detrended Corre- spondence Analysis (DCA) showed the time series varia- tions in community structure among treatments, in particular for imidacloprid during the middle stage of the experimental period. These results show the ecological effect-concentrations (LOEC * 1 lg/l) of these insecti- cides in mesocosms, especially imidacloprid, are clearly different from their laboratory tests. We suggest that differences in the duration of the recovery process among groups of species are due to different physicochemical properties of the insecticides. Therefore, realistic predic- tion and assessment of pesticide effects at the community level should consider not only the sensitivity traits and interaction among species but also the differences in physicochemical characteristics of each pesticide.
Abstract: Agricultural landscapes, including paddies, play an important role in maintaining biodiversity, but this biodiversity has been under the threat of toxic agro-chemicals. Our knowledge about how aquatic communities react to, and recover from, pesticides, particularly in relation to their residues, is deficient, despite the importance of such information for realistic environmental impact assessment of pesticides. The cumulative ecological impacts on aquatic paddy communities and their recovery processes after two successive annual applications of two systemic insecticides, imidacloprid and fipronil, were monitored between mid-May and mid-September each year. The abundance of benthic organisms during both years was significantly lower in both insecticide-treated fields than in the controls. Large-impacts of fipronil on aquatic arthropods were found after the two years. Growth of medaka fish, both adults and their juveniles, was affected by the application of the two insecticides. A Principal Response Curve analysis (PRC) showed the escalation and prolongation of changes in aquatic community composition by the successive annual treatments of each insecticide over two years. Residues of fipronil in soil, which are more persistent than those of imidacloprid, had a high level of impact on aquatic communities over time. For some taxonomic groups, particularly for water surface-dwelling and water-borne arthropods, the second annual treatment had far greater impacts than the initial treatment, indicating that impacts of these insecticides under normal use patterns cannot be accurately assessed during short-term monitoring studies, i.e., lasting less than one year. It is concluded that realistic prediction and assessment of pesticide effects at the community level should also include the long-term ecological risks of their residues whenever these persist in paddies over a year.
Abstract: The mode of action of insecticides is responsible for their higher or lower toxicity to non-target organisms. However, the large variations in susceptibility among different animal taxa indicate that certain biochemical traits particular to a group of organisms are responsible for a specific level of sensitivity. A review of toxicity data to non-target organisms is presented here. Aquatic arthropods are most susceptible to all types of insecticides because they share many physiological features with the target insects. Other aquatic organisms, such as fish and amphibians, are very sensitive to broad-spectrum neurotoxic and respiratory inhibitor insecticides, but not so much to selective insecticides such as IGRs and stomach poisons. Terrestrial vertebrates are also sensitive to most neurotoxicants and respiratory inhibitors, with the exception of those insecticides derived from natural toxins produced by plants or fungi (e.g. pyrethroids, neonicotinoids, avermectins, spinosad), which appear to have little or no toxicity in birds and mammals.
Abstract: A fundamental goal of toxicology is to determine safe levels of exposure to potentially poisonous substances for humans and the environment. Traditionally, safe levels of a chemical have been derived from the non-observable effect level (NOEL) estimated in laboratory toxicity bioassays with organisms which are representative of certain taxa. There are fundamental problems with the validity of this approach, both conceptual and statistical in nature. Firstly, the outdated NOEL concept is being replaced by the no-effect concentration (NEC) level, which assumes that toxic chemicals do not have any effect on a population of organisms at very low concentrations. Recent developments in ecotoxicology, however, suggest that some toxicants can produce effects at any concentration level provided their exposure time is sufficiently long. Consequently, risk assessment of these chemicals, which includes neonicotinoid insecticides, some carcinogenic substances and certain metallic compounds, may require entirely new approaches. Secondly, the traditional approach to toxicity testing is to consider dose or concentration-effect relationships at arbitrarily fixed exposure durations which are supposed to reflect ‘acute’ or ‘chronic’ time scales. This approach measures the proportion of all exposed individuals responding by the end of those fixed exposure times. However, the endpoint values obtained this way cannot be linked to make predictions for the wide range of exposures encountered by humans or in the environment, thus leading to serious underestimates of actual risk. In order to overcome this handicap, an increasing number of researchers are using a variant of the traditional toxicity testing protocol which includes time to event (TTE) methods. This TTE approach measures the times to respond for all individuals, and provides information on the acquired doses as well as the exposure times needed for a toxic compound to produce any level of effect on the organisms tested. Consequently, extrapolations and predictions of toxic effects for any combination of concentration and time are now made possible. Examples are shown to demonstrate that this approach is superior to current toxicological testing procedures, and has important implications for risk assessment of chemicals, particularly when the chemical has delayed toxic effects in a time-dependent manner.
Abstract: A comparison of environmental risks of pesticides between tropical and nontropical regions has been performed, using data from the literature and modeling outputs based on the physicochemical properties of the compounds. With a few exceptions, the level of risk of exposure for most pesticides in tropical agriculture is similar to that in other climatic regions of the world. Generally, dissipation of pesticides increases under the warm and wet conditions of the tropics, with most of the dissipation occurring through hydrolysis in water and biological degradation in water and soil. High temperatures in the tropics also foster volatilization rates, whereas high precipitation and poor soils tend to increase losses into runoff and, for certain chemicals, affects their leaching behavior. The environmental risk is determined by a balance of soil types, soil organic carbon, pH, and the rates of degradation in the various environmental compartments.
Abstract: The herbicides amitrole and glyphosate, and its metabolite aminomethyl phosphonic acid (AMPA), in water samples have been directly analysed by high-performance liquid chromatography using an electrochemical (EC) detector. Limits of detection of 0.3 μg mL−1 for glyphosate, 0.05 μg mL−1 for AMPA and 0.03 μg mL−1 for amitrole were comparable to those obtained by other authors using EC and also by liquid-chromatography coupled to mass spectrometry, but the latter method requires derivatisation and pre-concentration of the sample whereas EC methods show similar sensitivity without the need of any derivatisation. The method was specifically designed to analyse extracts from passive samplers used for monitoring of polar herbicide residues in waters. To this purpose, three types of Empore® disks were tested for their ability to adsorb and desorb these ionic, polar analytes. A procedure for their extraction from the membranes and reducing the interferences from other substances present in natural waters (i.e. humic acids) is described. The method is simple, does not require sophisticated equipment and is valid for the analysis and monitoring of herbicides residues using passive samplers.
Abstract: The influence of various diets on the survival, fecundity, and the polyunsaturated fatty acid (PUFA) composition of the benthic estuarine amphipod Melita plumulosa (Zeidler) in laboratory cultures were determined. Apart from a natural silty sediment, six commercial food supplements were examined: an omega-6 PUFA enriched Spirulina-based dry powder, Sera® micron; a shrimp-based pellet food; an omega-3 PUFA enriched algal paste, Rotiselco®-ALG; an omega-6 PUFA enriched algal dry powder, AlgaMac-ARA (arachidonic acid); flaxseed meal; and an omega-3 PUFA enriched dry powder, Frippak®. We have previously established that M. plumulosa cultures perform poorly and eventually decline if provided with silty sediment alone, but will thrive if supplemented with Sera micron. Conversely, if the amphipods are cultured on a nutrient-depleted sand substrate, Sera micron alone does not constitute an adequate feed. The major difference in the fatty acid composition of M. plumulosa cultured on silty sediment compared to amphipods cultured on a sand substrate and both fed Sera micron was an increase in the ratio of omega-3 to omega-6 PUFAs, indicating that the silty sediment provides additional food sources rich in omega-3 PUFAs. Furthermore, amphipods cultured in sand and fed any of the three algal-based foods or the Frippak powder as the sole food source had poor survival rates, although Sera micron maintained the best survival - this was attributed to it containing high amounts of -carotene and terpenoids. Melita plumulosa fed a mixture of Sera micron in conjunction with the omega-3 PUFA enriched Rotiselco-ALG and cultured on a silty substrate were found to have good fecundity with low variability.
Abstract: In the Coleambally irrigation area (NSW, Australia), the occurrence of four tadpole and frog species in rice bays on farms growing either rice only or both rice and corn was studied over two seasons. In addition to analysis of species occurrence, both gonadal histology and assessment of Batrachochytrium dendrobatidis infection rates were performed. The rice acreage available as potential tadpole habitat was extensively distributed throughout the irrigation area, but more corn was grown in the northern region compared with the southern region. The mean abundance of Litoria raniformis tadpoles was significantly lower in the northern sites compared with the southern sites. In contrast, tadpoles of Limnodynastes fletcheri, Limnodynastes tasmaniensis, and Crinia parinsignifera had a uniform distribution across all study sites. A principal components analysis showed a relationship between farm type and the rice herbicide applied when the crops were initially sown, with sites occupied by Litoria raniformis in the beginning being predominantly rice-only farms. A discriminant analysis showed that low concentrations of the corn herbicide metolachlor and increased pH were the main variables studied that determined site occupation by L. raniformis. This suggested that farms growing only rice (and not corn) with high algal production were the preferred sites. The rates of chytrid infection and gonadal malformations were low across both regions. Histology of the gonads of metamorphs showed that L. raniformis gonadal differentiation is slow compared to that of the two Limnodynastes species. We concluded that farm practices associated with increased corn cropping in the northern region, rather than any direct effect of corn herbicides, determine the reduced presence of Litoria raniformis in the northern region.
Abstract: The ability to predict the effects of toxicants in organisms with reasonable accuracy depends to a great extent on the toxico-kinetic models used to describe such effects. Toxic effects of organic chemicals and heavy metals have been described adequately using a hyperbolic model that considers the concentration of the toxicant and the time of exposure only. Such a model relies on the median time to effect (ET50) of a chemical to estimate effects at any exposure time, but cannot make predictions for concentrations other than those tested experimentally. A complementary log-to-log model can calculate all ET50 values for a toxicant, thus enabling the hyperbolic model to predict any level of effect for any combination of concentrations and times of exposure. The parameter values used in both models are obtained from experimental bioassays where the time-to-effect of a toxicant is recorded regularly in addition to standard acute or chronic toxicity data. These models will facilitate the risk assessment of chemicals by (1) predicting effects under any combination of time and concentrations, and (2) reducing to a minimum the experimental efforts required to obtain comprehensive ecotoxicity data.
Abstract: To elucidate the ecological impacts of imidacloprid [1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine] on vegetable crops and their surrounding areas, arthropods on eggplant patches treated with this insecticide were monitored throughout two cultivation seasons, spring and autumn, and the results compared with those of control crops. Residues of imidacloprid in soil accounted for 4-8% of total applied, and concentrations outside the crop were always below 5 ug/kg. Communities of the crop vegetation experienced significant density reductions, mostly of aphids, and had fewer species diversity during the first month. Those in the surrounding pasture were similarly affected though with less intensity, while non-target ground arthropods both inside and outside the crop only showed significant impacts in the two weeks after planting.
Abstract: The basis of ecotoxicology lies currently in the dose-response of organisms to toxicants, as typically described by probit and logistic models. While recognizing its merits, standard endpoints ignore the process of toxicity with time, and consequently our ability to predict direct toxic effects in environmental risk assessments is seriously curtailed. Although the response of toxicants with time has been studied before, its application in ecotoxicology remains underutilized. One reason is that no convincing mechanism has been proposed to explain the hyperbolic curves of such responses, whereas a variety of models have been used to describe them. The explanation of both time- and dose-dependent responses is found ultimately in the natural variability of receptor sites among individuals of populations exposed to a toxicant inhibitor with time. The process can be explained by the kinetics of inhibition, and is appropriately described by a simple mathematical expression like the Michaelis-Menten equation, though other asymptotic models (e.g. logistic model) can also be used. The advantage of the hyperbolic model is that median effect values (e.g. LC50 for dose- and ET50 for time-dependent responses) enable calculation of toxicity effects at any concentration level and/or time of exposure, thus making it especially attractive for risk assessment.
Abstract: Ecological changes due to the insecticide imidacloprid and a pollutant from anti-dandruff shampoos (zinc pyrithione) were monitored in experimental paddies throughout a cultivation period. A total of 88 species were observed, 54 of them aquatic. Plankton, nekton, benthic and terrestrial communities from imidacloprid fields had significantly less abundance of organisms than control and shampoo-treated fields, either for the entire period or in early stages. The absence of Chironomus yoshimatsui and typical paddy ostracods from imidacloprid fields was most remarkable; as a consequence, green algae blooms (Spirogyra sp.) developed, which in turn hampered the establishment of weeds. Such changes occurred while residues of imidacloprid in water were present at levels above 1μg/L. The overall diversity was similar in all fields, and increased constantly until the end of the study. Phytophagous insects dominated in early communities, giving way gradually to predators and scavengers in late stages, but imidacloprid fields had a lower proportion of the latter trophic group. Multivariate analyses helped describe and differentiate the communities between treatments and control. Hazard and risk assessment methods overestimated the effects of zinc pyrithione while failed to predict imidacloprid impacts, probably because of deficiencies in the exposure and relevant toxicity data used.
Abstract: The acute toxicity of imidacloprid, a neonicotinoid insecticide, and zinc pyrithione (Zpt), a biocide used in anti-dandruff shampoos and protective antifouling paints, to three species of ostracods and two waterfleas, including Daphnia magna, was determined and compared under light and dark conditions. Under normal laboratory conditions, UV light had no significant influence on the outcome of toxicity bioassays, although in the case of imidacloprid both EC50 and LC50 calculated values were twice as high under the light as in the dark. No influence of UV light was observed on bioassays conducted with Zpt, in spite of the fast aqueous photolysis exhibited by this compound. Imidacloprid 48-h LC50 for cladocerans (65–133 mg/L) were two orders of magnitude higher than for ostracods (301–715 μg/L); values of EC50 for cladocerans and ostracods were 2–6 mg/L and 3–16 μg/L, respectively. Toxicity of Zpt to both ostracod and cladoceran species appears to be similar, with 48-h LC50 in the range 137–524 and 75–197 μg/L for ostracods and cladocerans, respectively, and similar values for EC50s. The mortality endpoint (LC50), however, is not a reliable predictor of the effects of imidacloprid under field situations (e.g. rice paddies), because the paralysis effect induced by this insecticide takes place at much lower concentrations than those required to cause the death of the animals: regardless of the taxa, differences as large as 100- or 600-fold were observed between the EC50 and LC50 for the same exposures. As a consequence, immobilization tests and EC50 values are recommended for this class of compounds, while caution should be exercised in environmental risk assessments of this and possibly other related neonicotinoid insecticides with similar activity.
Abstract: A pilot-scale, ponded wetland consisting of an open pond and a vegetated pond in series was constructed on a cotton farm in northern New South Wales, Australia, and assessed for its potential to remove pesticides from irrigation tailwater. Ten incubation periods ranging from 7 to 13 days each were conducted over two cotton growing seasons to monitor removal of residues of four pesticides applied to the crop. Residue reductions ranging 22–53% and 32–90% were observed in the first and second seasons respectively. Average half-lives during this first season were calculated as 21.3 days for diuron, 25.4 days for fluometuron and 26.4 days for aldicarb over the entire wetland. During the second season of monitoring, pesticide half-lives were significantly reduced, with fluometuron exhibiting a half-life of 13.8 days, aldicarb 6.2 days and endosulfan 7.5 days in the open pond. Further significant reductions were observed in the vegetated pond and also following an algal bloom in the open pond, as a result of which aldicarb and endosulfan were no longer quantifiable. Partitioning onto sediment was found to be a considerable sink for the insecticide endosulfan. These results demonstrate that macrophytes and algae can reduce the persistence of pesticides in on-farm water and provide some data for modelling.
Abstract: The acute toxicity of 468 organic pollutants to planktonic crustaceans (Branchiopoda, Copepoda and Ostracoda) from pre-existing data was compared by means of statistical analysis and relative tolerance indices (Trel). A surrogate species commonly used in toxicity bioassays (Daphnia magna) showed toxicity levels – within one order of magnitude – similar to all other Cladocera species, at least for 82% of the chemicals studied. All neurotoxic insecticides except neonicotinoids, PCBs, organometallic compounds and PAHs are the most toxic substances to these organisms. Sensitivity levels among taxa were compared for individual chemicals as well as groups of chemicals with similar characteristics. Whilst there are marked differences in sensitivity among taxa and particular groups of chemicals, no consistent trends were found for freshwater and saltwater species in relation to the latter groups. No correlation between LC50 and size of these organisms was found other than by chance, making extrapolations based on allometric equations impossible.
Abstract: Biological effects of the biocide zinc pyrithione (Zpt), used in anti-dandruff shampoos and antifouling paints and the agricultural insecticide imidacloprid on Japanese medaka fish (Oryzias latipes) were assessed in experimental rice fields. Both chemicals are toxic to medaka, in particular Zpt, which also causes teratogenic effects such as spinal cord deformities in embryos at very low, sublethal concentrations. Rates of malformation in medaka fry from paddies treated twice a week with anti-dandruff shampoo (0.18–0.37 μL/L each time) over a period of 4 months were within the natural background, perhaps due to the quick dissipation rate of this chemical in the environment. Both Zpt and imidacloprid caused stress syndrome in juvenile medaka, with fish from Zpt-shampoo fields having a significantly lower weight to body length ratio than those from control fields. As it often happens with stressed fish, a massive infestation by a Trichodina ectoparasite was observed in medaka from imidacloprid fields. However, despite their high stress levels, fish from the Zpt fields did not suffer such infestation, supposedly because the disinfectant action of this biocide.
Abstract: Although the use of endosulfan to control cotton pests has declined, this insecticide still has widespread application in agriculture and can contaminate riverine systems as runoff from soil or by aerial deposition. The degradation of endosulfan in pure water at different pH values of 5, 7 and 9 and in river water from the Namoi and the Hawkesbury rivers of New South Wales (NSW), Australia, was studied in the laboratory. Endosulfan transformation into endosulfan sulfate in river water using artificial mesocosms was also investigated. The results show endosulfan is stable at pH 5, with increasing rates of disappearance at pH 7 and pH 9 by chemical hydrolysis. Incubation of endosulfan with river water at pH 8.3 resulted in the disappearance of endosulfan and the formation of endosulfan diol due to the alkaline pH as well as formation of endosulfan sulfate. Although the degradation of endosulfan by Anabaena, a blue-green alga, did not result in the transformation of endosulfan to endosulfan sulfate, we conclude that other microorganisms catalyzed the formation of the sulfate. Significant conversions of endosulfan into endosulfan sulfate were also reported from associated field studies using artificial mesocoms containing irrigation water from rivers inhabitated by micro-macro fauna. From these results, we conclude that the presence of endosulfan sulfate in river water cannot be used to distinguish contamination by runoff from soil from contamination by aerial drift or redeposition.
Abstract: Given the strict protocols for the registration of agrochemicals in developed countries there is a need to re-consider whether the use of PECs for the assessment of risks and/or hazards in aquatic environments is a valid approach. As the exposure of aquatic organisms in natural systems is reduced by several processes, more realistic values of effective concentrations should be estimated. A correcting factor for such effective exposure is proposed here based on the partitioning and dissipation features of organic pesticides. The validation of this model is limited by the data available at the moment, but the evidence so far is quite promising.
Abstract: A site-specific methodology was developed to assess and compare the ecotoxicological risk that agricultural pesticides pose to ecosystems. The Ecological Relative Risk (EcoRR) is a composite scoring index for comparing relative risks between different plant protection products, and is used to assess the potential ecological impact their residues have after being applied to agricultural systems. The EcoRR model is based on standard frameworks for risk assessment (e.g. PEC/toxicity), but takes account of factors such as persistence of residues and biodiversity of ecosystems. The exposure module considers the environmental concentrations of a substance, its persistence, bioaccumulation and probability of exposure in several environmental compartments (water, sediment, soil, vegetation, air). The toxicity module takes into account the biodiversity of the ecosystems affected, whereby the endpoints used are weighted by the proportional contribution of each taxon in a given environmental compartment. EcoRR scores are calculated independently for each compartment and affected areas, thus enabling pinpointing of where risks will occur. The procedure to calculate EcoRR scores is explained using an example, and a sensitivity analysis of the model is included. A simulated risk assessment of 37 pesticides intended for use in a cotton development is also given as a case study. Exposure data were obtained using fugacity model II in areas previously defined by spray drift models. Toxicity data to vertebrate taxa and crustaceans were obtained from several databases, and biodiversity data from local sources. EcoRR scores were calculated for each compartment both on-farm and off-farm, during a normal growing season and during a flood, and a comparative relative assessment for all pesticides is discussed. EcoRR scores were also compared to traditional assessments using quotients for some taxa in the aquatic and terrestrial environments, revealing a good correlation between both models in some cases. It is apparent that EcoRR scores reflect adequately the potential risk of those chemicals to ecosystems, though they are less dependent on toxicity to sensitive species than the simple quotient. This methodology can be used either with field measured data or model predicted data, so management options for new chemicals can be tested prior to their application on crops.
Abstract: Chlorpyrifos [O,O-diethyl O-(3,5,6-trichloro-2-pyridyl) phosphorothioate] is the most widely used soil-applied termiticide in Australia. It is relatively stable, has low water solubility, is absorbed by organic matter, and has a high affinity for soil with low partitioning potential from soil matter to soil water. The purpose of this degradation study is to determine the effect of soil alkalinity on the longevity of termite protection when chlorpyrifos is applied as a termiticide in a range of Australian soils, particularly high-pH substrates. The study also examines the effects of initial soil concentration on the degradation of chlorpyrifos in the range of soils. At an initial soil concentration of 1000 mg kg-1 for termite control, the degradation rate of chlorpyrifos is very strongly retarded in soils tested when compared with lower soil concentrations of 100 and 10 mg kg-1 in the same soils. The degradation data correlated with a logarithmic model of decay, and it was thus possible to produce half-lives and predict likely periods of termite control. Average half-lives for all soils for the three concentrations were 385, 155, and 41 days, respectively. Soil pH had no effect on the rate of degradation at all concentrations tested.
Abstract: The fate and transport of endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepin 3-oxide) applied to cotton (Gossypium hirsutum L.) fields were studied throughout three consecutive years on two selected locations in New South Wales (Australia). Rates of dissipation from foliage and soil, volatilization from the field, and transport of residues in irrigation and/or storm runoff waters were measured in order to estimate a total field balance. Dissipation of endosulfan from both foliage and soil is best explained by a two-phase process rather than by a first-order decay. Half-lives of total endosulfan toxic residues (- and s-endosulfan and the sulfate product) in the first phase were 1.6 d in foliage and 7.1 d in soil, and could be explained by the rapid volatilization of the parent isomers in the first 5 d (up to 70% of endosulfan volatilizes). In the second phase, half-lives were 9.5 d in foliage and 82 d in soil, mostly due to the persistence of the sulfate product. Concentration of endosulfan residues in runoff water varied from 45 to 2.5 ìg L-1 depending on the residue levels present on field soil at the time of the irrigation or storm events. These in turn are related to the total amounts applied, the cotton canopy cover at application, and the time since last spraying. Most of the endosulfan in runoff was found in the water phase (80%), suggesting it was bound to colloidal matter. Total endosulfan residues in runoff for a whole season accounted for no more than 2% of the pesticide applied on-field.
Abstract: Current methods to analyse pesticide residues in wild animals are essentially forensic examination procedures. This paper describes a new approach to obtain samples from live birds for pesticide residue analysis without harm to the animal involved. The technique measures the dietary exposure and has been tested successfully in birds exposed to farm chemicals in Australia. Stomach flushing with warm water was used to obtain 'flushing' samples (stomach and droppings combined) from 11 species of birds at four locations near or away from cotton farms. Water samples from all sites were also taken. Immunoassays were used to analyse these samples for residues of DDE, DDT, diuron, endosulfan and parathion-methyl. ELISA is suited to environmental residue analysis because of its high sensitivity, small sample volume requirements, low cost and speed. Prior to the residue analysis, optimization of the assays and elimination of matrix effects are essential. Positive residues were found in 90% of the birds, their amounts varying up to 4 orders of magnitude amongst individuals and species, with predators and insectivorous having higher levels than granivorous and nectivores. The technique can be applied to the same animal over a period of time, thus providing a useful tool for monitoring programs in environmental studies. Its application to ecological risk assessment and exposure are discussed.
Abstract: Germination and survival of seedlings of four woody weed species were examined in western New South Wales (Australia) between 1979-82. Conditions favourable to large scale establishment depended mainly on rainfall during late autumn and winter for germination, followed by summer rainfall for survival of the seedlings. Soil disturbance enhanced seedling emergence of some species by increasing soil moisture content deep in the soil profile. Micro-depressions and sandplains favoured survival of all species. Grazing had no specific impact on emergence of any of the species, but reduced the survivorship of some. Predation by insects had a negligible effect. Management options for encroaching shrub populations are discussed.
Abstract: Growth and survival of four woody weed species were examined in relation to the effects of grazing and shrub density in western New South Wales (Australia) between 1979-82. All species showed a high survival rate, particularly in height classes above 25 cm, and kept growing during drought periods. The effects of grazing on survival were inconclusive. Competition with woollybutt (perennial grass) and annual herbage was studied. Woollybutt biomass was negatively affected by the proximity of shrubs. Annual herbage did not have any effect on shrubs' survival, but shrub seedlings grew better under moderate herbage cover. The characteristics of these species help explain their competitive advantage over herbaceous plants, particularly in times of droughts.
Abstract: Imbibition and germination of seeds of three Acacia species from Ethiopia, namely Acacia nubica, A. seyal and A. horrida, were tested in laboratory conditions. Heat treatments had a positive effect on imbibition rates for all three species. The best treatment was 60 degree C for two hours, a longer time of exposure having a negative effect on the seeds, A positive response to light was detected in A. nubica and A. seyal, while seeds of A. horrida responded with indifference to light. A high degree of hard-seededness - over 90% - was common in all three species. Although temperature had a positive effect on germination rates, only scarification of seeds proved to be effective in overcoming hard-seededness.
Abstract: Three Acacia species from Ethiopia, namely Acacia nubica, A. seyal and A. horrida, were tested for growth and resistance to drought during the establishment phase in glasshouse and laboratory conditions. The experiments showed that each species has different preferences for particular environmental conditions. Temperature, water availability and depth of sowing were the most important factors affecting the growth of these plants. Soil type had a similar effect on all of them, sandy and loamy conditions being preferred to clay. Acacia nubica and A. horrida proved to respond positively to hot environments, although the first species requires a good water supply and the second is capable of growing under water shortages. Acacia seyal seems better adapted to sub-humid climate types. A high resistance to drought conditions was a common characteristic of all three species: survival after 24 days without any water under high evaporation conditions proves that these Acacia species, particularly A. horrida, are well adapted to cope with harsh droughts.
Abstract: Pesticides are toxic chemicals used to control pests, weeds and pathogens. Three quarters of all pesticides are employed in agricultural production, particularly in developed countries, in an effort to mitigate crop damage endured by intensive agriculture. However, after more than 60 years of worldwide usage, their side-effects on terrestrial ecosystems – even when applied as recommended – are obvious. This chapter examines the ecological problems caused by specific chemicals/groups, so that this awareness may help improve agricultural practices through appropriate risk management. Fungicides alter the microbial-fungi communities responsible for the recycling of nutrients in the soil, and copper fungicides are toxic to earthworms and other animals. The routine application of herbicides has produced a net loss of plant biomass and biodiversity in many landscapes, which indirectly reduces the associated arthropod communities and leads to population declines in many species of birds, and possibly amphibians too, due to lack of food. Insecticides are very toxic to most invertebrates in the soil, birds and small mammals, causing significant reductions in their populations and disturbing the trophic structure of their communities. Persistent pesticides accumulate in soil and concentrate through the trophic chain, causing a plethora of sublethal effects which are negative for the survival of individuals as well as the viability of their populations; the long term effects of DDT and cyclodiene poisoning in birds is still an ecological issue despite more than 30 years of not being applied in most developed countries. While pesticides have increased our agricultural productivity and helped feed the current human population, the price of this productivity is being paid by the Earth’s ecosystems at large.
Abstract: The known ecological impacts of insecticides on terrestrial and aquatic ecosystems are reviewed in this chapter. Awareness of the impacts that insecticides are having in our world may help introduce management practices that aim at reducing and mitigating those impacts. We must accept that pest control and disease eradication are complex issues that will never be resolved without causing problems to the environment – our aim should be to minimise the environmental impacts to levels that are acceptable by the society and bearable by the ecosystems. However, the environmental pollution brought about by the constant use of pesticides and their subtle undermining of the ecosystems should not be dismissed as trivial. Ultimately, we all depend on the services that the environment provides for our own health and food production.
Abstract: Modern living standards depend largely on the production and usage of thousands of chemicals, many of which are toxic and synthetically produced. These substances are discharged into the air, soil, water bodies and the sea through a variety of ways, becoming pollutants of our environment. The investigation of their fate and impacts they have on ecosystems is called ecotoxicology, a multidisciplinary science which intends to evaluate the nature of the discharge, the transformation and distribution of toxicants in the environment, exposure, lethality and sublethal effects on organisms, population responses, and changes in community structure and ecosystem function. The sources and mode of action of some of the most common groups of toxicants are described in this chapter, leaving their fate and effects in organisms and ecosystems for the subsequent chapters.
Abstract: Selection of agrochemicals that may control pest outbreaks while ensuring smaller impacts on the environment is important for the success of IPM. Currently, regulators evaluate risks from chemicals following a tiered system which relies heavily on the quotient method. To test the validity of two current models used for risk assessment, impacts of two insecticides and a pollutant on a mesocosms agro-ecosystem were monitored during two rice growing seasons. Whilst some of the observed effects on populations agreed with the models’ predictions, inadequacies of such methods stemmed from unknown exposure mechanisms under natural environments, inappropriate toxicity data derived under laboratory conditions and omission of the physical and chemical properties of the compounds in the quotient model. This validation study provides an opportunity to reconsider current risk approaches.
Abstract: Agrochemicals will remain essential for economic production of the bulk of the world’s food and fibre. However, their continued acceptance as agents for the control of pests has required a remarkable evolution in applied chemistry. To guarantee increasing environmental safety, an ongoing process of rational human action is needed, based on chemical risk assessment, chemical monitoring and risk management using information of the highest possible quality as feedback
Abstract: Preventing contamination of the environment and of agricultural produce with pesticide residues is a complex task. In Australia, an extensive program of research for the cotton industry was undertaken to reduce the level of contamination by a wide range of pesticides. In this paper, several case studies are examined to demonstrate a comprehensive approach to tackle this issue. It involved the development of new ELISA assays for specific and sensitive screening of residues; studies of pesticide sorption in soil, aerial transport, movement in water runoff and sedimentation. The role of traceback to determine the causes of produce contamination, and fugacity modeling to carry out ecological risk assessment are also considered.
Abstract: Despite measures taken to reduce reliance on chemicals, production of Australian cotton still involves significant outputs of pesticides, with potential to contaminate other agricultural produce and the riverine environment. The environmental fate and transport of pesticides in cotton growing have been extensively monitored since 1993 to minimize their impact as chemical residues. This research focused on endosulfan as the major insecticide applied to cotton farms, and as a model for other chemicals. The results of this research help provide more sustainable practices in Australian cotton production.
Abstract: From a comprehensive study of the fate of endosulfan, following its application in cotton production systems, the mechanisms by which its residues dissipate and are transported off-field were determined quantitatively. Dissipation of endosulfan in the field occurs mainly through volatilization in the first 2-3 weeks after application. Residues in foliage of cotton plants are quickly degraded, whereas their degradation in soil takes much longer, partly because of the formation of endosulfan sulphate. The implications of these findings for management of cotton farms to protect the riverine environment are discussed.
Abstract: The Australian cotton industry has been the focus of significant research on pesticide managemnt with a view to reduce its impact on the riverine ecosystems and the contamination of agricultural produce such as beef. In this paper, pesticides such as endosulfan, pyrethroids and chlorfluazuron have been examined for aerial transport in drift, erosion of cotton fields in surface runo-off and their rate of dissipation from the environment. The outcome sought was to develop a manual of best practices for the cotton industry that would minimize the impact of the 30-40 different insecticides and 20 herbicides used in cotton production.
