Do magnesium and chloride ameliorate high sodium bicarbonate concentrations? A comparison between laboratory and mesocosm toxicity experiments.

Increasing salinity is a concern for biodiversity in many freshwater ecosystems globally. Single species laboratory toxicity tests show major differences in freshwater organism survival depending on the specific ions that comprise salinity types and/or their ion ratios. Toxicity has been shown to be reduced by altering ionic composition, despite increasing (total) salinity. For insistence, single species tests show the toxicity of sodium bicarbonate (NaHCO3, which commonly is a large proportion of the salts from coalbeds) to freshwater invertebrates is reduced by adding magnesium (Mg2+) or chloride (Cl-). However, it is uncertain whether reductions in mortality observed in single-species laboratory tests predict effects within populations, communities and to ecosystem processes in more complex multi-species systems both natural and semi-natural. Here we report the results of an outdoor multi-species mesocosm experiment to determine if the effects of NaHCO3 are reduced by increasing the concentrations of Mg2+ or Cl- on: a) stream macroinvertebrate populations and communities; b) benthic chlorophyll-a and; c) the ecosystem process of leaf litter decomposition. We found a large effect of a high NaHCO3 concentration (≈4.45 mS/cm) with reduced abundances of multiple taxa, reduced emergence of adult insects and reduced species richness, altered community structure and increased leaf litter breakdown rates but no effect on benthic chlorophyll-a. However, despite predictions based on laboratory findings, we found no evidence that the addition of either Mg2+ or Cl- altered the effect of NaHCO3. In semi-natural environments such as mesocosms, and natural environments, organisms are subject to varying temperature and habitat factors, while also interacting with other species and trophic levels (e.g. predation, competition, facilitation), which are absent in single species laboratory tests. Thus, it should not be assumed single-species tests are good predictors of the effects of changing ionic compositions on stream biota in more natural environments.

Epidemiology of cruciate ligament reconstruction in the Australian Defence Force and predictors of outcome.

BACKGROUND: The ability to predict the risk of poor outcome following knee cruciate ligament reconstruction in the Australian Defence Force (ADF) population would help direct individual rehabilitation programmes and workforce planning. This study describes the epidemiology of cruciate ligament reconstruction in the ADF and demonstrates the use of Bayesian networks (BN) to predict the likelihood of fitness for ongoing service under different scenarios. METHODS: Members who had knee cruciate ligament reconstruction through ADF were identified from billing data and matched to electronic medical records to extract demographic and clinical data. Outcome measure was medical fitness for ADF service up to 24 months after reconstruction. BN models were used to compare outcomes between (1) age groups according to military service, and (2) sexes according to body mass index (BMI). RESULTS: From November 2012 to June 2019, a total of 1199 individuals had knee cruciate ligament reconstruction (average 169 reconstructions/year). Following reconstruction and rehabilitation, 89 (7.4%) were medically unfit for service. Scenario analysis using a tree-augmented naïve BN model showed that, compared with Navy and Air Force, Army members had a higher probability of being unfit in those aged <35 years and a lower probability in those aged ≥35 years. In both sexes, those with obese BMI had the greatest probability of being unfit. CONCLUSION: While most ADF members were fit for ongoing military service following cruciate ligament reconstruction, service type, age, sex and BMI influenced outcome. BNs provided an interactive and intuitive method to demonstrate the impact of different variables on the outcome.

Bicarbonate alone does not totally explain the toxicity from major ions of coal bed derived waters to freshwater invertebrates.

Concentrations of major ions in coal mine discharge waters and unconventional hydrocarbon produced waters derived from coal bed methane (CBM) production, are potentially harmful to freshwater ecosystems. Bicarbonate is a major constituent of produced waters from CBM and coal mining. However, little is known about the relative toxicity of differing ionic proportions, especially bicarbonate, found in these CBM waters. As all freshwater invertebrates tested are more acutely sensitive to sodium bicarbonate (NaHCO3) than sodium chloride (NaCl) or synthetic sea water, we tested the hypotheses that toxicity of CBM waters are driven by bicarbonate concentration, and waters containing a higher proportion of bicarbonate are more toxic to freshwater invertebrates than those with less bicarbonate. We compared the acute (96 h) lethal toxicity to six freshwater invertebrate species of NaHCO3 and two synthetic CBM waters, with ionic proportions representative of water from CBM wells across New South Wales (NSW) and Queensland (Qld), in Australia. The ranking of LC50 values expressed as total salinity was consistent with the hypotheses. However, when toxicity was expressed as bicarbonate concentration, the hypothesis that the toxicity of coal bed waters would be explained by bicarbonate concentration was not well supported, and other ionic components were either ameliorating or exacerbating the NaHCO3 toxicity. Our findings showed NaHCO3 was more toxic than NaCl and that the NaHCO3 proportion of synthetic CBM waters drives toxicity, however other ions are altering the toxicity of bicarbonate.

Species of freshwater invertebrates that are sensitive to one saline water are mostly sensitive to another saline water but an exception exists.

Coal mining and extraction of methane from coal beds generate effluent with elevated salinity or major ion concentrations. If discharged to freshwater systems, these effluents may have adverse environmental effects. There is a growing body of work on freshwater invertebrates that indicates variation in the proportion of major ions can be more important than salinity when determining toxicity. However, it is not known if saline toxicity in a subset of species is representative of toxicity across all freshwater invertebrates. If patterns derived from a subset of species are representative of all freshwater invertebrates, then we would expect a correlation in the relative sensitivity of these species to multiple saline waters. Here, we determine if there is a correlation between the acute (96 h) lethal toxicity in freshwater invertebrates to synthetic marine salts (SMS) and sodium bicarbonate (NaHCO3) added to dechlorinated Sydney tap water. NaHCO3 is a major component of many coal bed effluents. However, most salinization in Australia exhibits ionic composition similar to seawater, which has very little HCO3- Across all eight species tested, NaHCO3 was 2-50 times more toxic than SMS. We also observed strong correlations in the acute toxicity of seven of the tested species to SMS and NaHCO3 The strongest relationship (LC50 r2 = 0.906) was dependent on the exclusion of one species, Paratya australiensis (Decopoda: Atyidae), which was the most sensitive species tested to NaHCO3, but the second-most tolerant of SMS. We conclude that differences in the toxicity of different proportions of major ions can be similar across a wide range of species. Therefore, a small subset of the invertebrate community can be representative of the whole. However, there are some species, which based on the species tested in the current study appear to be a minority, that respond differently to saline effluent and need to be considered separately. We discuss the implications of this study for the management of saline coal bed waters.This article is part of the theme issue 'Salt in freshwaters: causes, ecological consequences and future prospects'.

Management of post-operative acute kidney injury.

Post-operative acute kidney injury (AKI) is a common complication of surgery with significant short- and long-term adverse consequences. The adoption of diagnostic criteria for AKI (RIFLE, AKIN and KDIGO) has facilitated comparison of data reported by different centres, confirming that even mild AKI is associated with excess mortality. It remains unclear whether this is caused by the kidney injury itself or whether AKI is simply a marker of underlying disease severity. There is no trial evidence to support the use of any specific therapeutic intervention in post-operative AKI. Best current treatment is, therefore, preventative by optimizing hydration and avoidance of nephrotoxins, emphasizing the importance of earlier detection and identification of individuals at high risk for AKI. In this review, we examine the latest literature on the management of post-operative AKI in adult patients, specifically the diagnosis and definition of AKI, epidemiology and pathogenesis and risk stratification in cardiac and non-cardiac surgery. We also review the latest evidence on pharmacological and non-pharmacological interventions.

Statistical analysis of support thickness and particle size effects in HRTEM imaging of metal nanoparticles.

High-resolution transmission electron microscopy (HRTEM) examination of nanoparticles requires their placement on some manner of support - either TEM grid membranes or part of the material itself, as in many heterogeneous catalyst systems - but a systematic quantification of the practical imaging limits of this approach has been lacking. Here we address this issue through a statistical evaluation of how nanoparticle size and substrate thickness affects the ability to resolve structural features of interest in HRTEM images of metallic nanoparticles on common support membranes. The visibility of lattice fringes from crystalline Au nanoparticles on amorphous carbon and silicon supports of varying thickness was investigated with both conventional and aberration-corrected TEM. Over the 1-4nm nanoparticle size range examined, the probability of successfully resolving lattice fringes differed significantly as a function both of nanoparticle size and support thickness. Statistical analysis was used to formulate guidelines for the selection of supports and to quantify the impact a given support would have on HRTEM imaging of crystalline structure. For nanoparticles ≥1nm, aberration-correction was found to provide limited benefit for the purpose of visualizing lattice fringes; electron dose is more predictive of lattice fringe visibility than aberration correction. These results confirm that the ability to visualize lattice fringes is ultimately dependent on the signal-to-noise ratio of the HRTEM images, rather than the point-to-point resolving power of the microscope. This study provides a benchmark for HRTEM imaging of crystalline supported metal nanoparticles and is extensible to a wide variety of supports and nanostructures.

Kinesiología y enfermedad pulmonar obstructiva crónica / Physical therapy and chronic obstructive pulmonary disease

Los pacientes con Enfermedad Pulmonar Obstructiva Crónica (EPOC) junto con desarrollar las alteraciones respiratorias propias de la patología desarrollan también alteraciones multisistémicas que repercuten principalmente en la musculatura respiratoria y periférica, reduciendo la capacidad de tolerancia física del paciente a las actividades diarias, Junto al tratamiento médico, la kinesiología representa una importante herramienta terapéutica, ya que se orienta a mantener las capacidades físicas del paciente, tanto en sus condicionantes respiratorias como motoras, El objetivo de este artículo es mostrar la importancia de la kinesiología en este grupo de pacientes, tanto durante su periodo de hospitalización como en el período de rehabilitación después del alta.

The majority of patients with Chronic Obstructive Pulmonary Disease (COPD) develop the classic respiratory alterations, as well as systemic dysfunctions, by which contribute to the deterioration of the respiratory and the skeletal muscles. Consequently, all of this muscle dysfunction reduce the physical capacity in the COPD patients to develop their diary activities, The physical therapy as a complementary treatment of the medical management, is an important therapeutic tool to maintain the physical abilities of the COPD patients as much in the respiratory function as in the motor area, This paper attempts to review the importance of the physical therapy in the COPD patients, such as in the hospitalization time and in the consecutive rehabilitation time.

Bicarbonate toxicity to Ceriodaphnia dubia and the freshwater shrimp Paratya australiensis and its influence on zinc toxicity.

Bicarbonate is often a major ionic constituent associated with produced waters from methane gas extraction and coal mining, yet few studies have determined its specific toxicity. Currently, the environmental risk of bicarbonate anion in water discharges is assessed based on the toxicity of sodium chloride or artificial seawater and is regulated via electrical conductivity. Increased NaHCO(3) added to Ceriodaphnia dubia in synthetic or natural water gave similar 48-h 10% effective concentration (EC10) values of 1750 ± 125 mg NaHCO(3)/L (mean ± standard error) and 1670 ± 180 mg NaHCO(3)/L, respectively. Bicarbonate was toxic to C. dubia in both waters with conductivities above 1900 µS/cm. In contrast, when conductivity was elevated with NaCl, toxicity to C. dubia was observed only above 2800 µS/cm. Bicarbonate also impaired C. dubia reproduction with an EC10 of 340 mg NaHCO(3)/L. Major ion composition also influenced Zn bioavailability, a common co-occurring metal contaminant in coal mine waters, with sublethal concentrations of NaHCO(3) and elevated pH increasing Zn toxicity. Higher pH was the dominant parameter determining a 10-fold increase in the 48-h 50% effective concentration (EC50) for Zn toxicity to C. dubia at pH 8.6 of 34 µg Zn/L (95% confidence limit = 32-37 µg Zn/L) compared with the Zn toxicity at approximately circumneutral pH. Exposure of the freshwater shrimp Paratya australiensis (Atyidae) in natural water to increasing bicarbonate gave a mean 10-d 10% lethal concentration (LC10) of 850 ± 115 mg NaHCO(3)/L, associated with a mean conductivity EC10 of 1145 µS/cm, which is considerably lower than toxicity of NaCl and artificial seawater to this species reported elsewhere. Because toxicity was influenced by salt composition, specific ions should be regulated rather than conductivity alone in mine wastewater discharges.

Detection and analysis of neonicotinoids in river waters--development of a passive sampler for three commonly used insecticides.

Increasing and widespread use of neonicotinoid insecticides all over the world, together with their environmental persistence mean that surface and ground waters need to be monitored regularly for their residues. However, current multi-residue analytical methods for waters are inadequate for trace residue analysis of these compounds, while passive sampling devices are unavailable. A new method using UltraPerformance Liquid Chromatography provided good separation of the five most common neonicotinoid compounds, with limits of quantitation in the range 0.6-1.0ng. The method was tested in a survey of rivers around Sydney (Australia), where 93% of samples contained two or more neonicotinoids in the range 0.06-4.5µgL(-1). Styrenedivinylbenzene-reverse phase sulfonated Empore™ disks were selected as the best matrix for use in passive samplers. Uptake of clothianidin, imidacloprid and thiacloprid in a flow-through laboratory system for 3weeks was linear and proportional to their water concentrations over the range 1-10µgL(-1). Sampling rates of 8-15mLd(-1) were correlated to the hydrophobicity of the individual compounds. The passive samplers and analytical methods presented here can detect trace concentrations of neonicotinoids in water.

Differential survival and reproductive performance across three mitochondrial lineages in Melita plumulosa following naphthalene exposure.

Populations subject to anthropogenic contaminants often display altered patterns of genetic variation, including decreased genetic variability. Selective pressures of contaminant exposure are also reflected in differential tolerance between genotypes. An industrial chemical spill in a major eastern Australian waterway in July 2006 resulted in altered patterns of genetic variability in a nearby population of the amphipod, Melita plumulosa for up to one year post-spill, despite the site being declared clean after 48 h. Here, we investigate the toxicant response of three mitochondrial lines naturally occurring at the impacted site by comparing survivorship and life-history trait variables following naphthalene exposure. Overall, M. plumulosa demonstrated differential survivorship between mitochondrial lines under exposure to high concentrations of naphthalene. In addition, we identified differential fecundity and frequencies of gravidity in female amphipods between the mitochondrial haplotypes examined. These findings suggest that the patterns of genetic variability previously identified may be linked with differential tolerance and/or reproductive performance between mitochondrial lineages.

Secondary vitellogenesis persists despite disrupted fecundity in amphipods maintained on metal-contaminated sediment: X-ray fluorescence assessment of oocyte metal content.

Melita plumulosa is an epibenthic, detritivorous amphipod found in estuaries along the eastern coast of Australia. It has been utilized as a test organism in rapid ten to thirteen days reproduction toxicity tests for sediment quality assessment. The fecundity of females in the toxicity test has been found to be inhibited by exposure of the amphipods to contaminated sediments enriched with zinc and other metals. This study investigated the proposal that interference in vitellogenesis is the cause of reproductive toxicity of metals in crustaceans. Inspection of the ovaries from amphipods on day 6 of the test either from control or Zn/Pb/Cd/Cu-spiked sediment, that were nearing completion of vitellogenesis, showed that the females in all treatments were producing similar numbers of oocytes undergoing secondary vitellogenesis. The distribution of the Zn, Cu and Pb in the oocytes and ventral caeca of females was examined by X-ray fluorescence microscopy. Elemental mapping revealed a dense accumulation of Zn in primary oocytes and a uniform distribution of Zn and Cu in the secondary oocytes in all treatments. Zn and Cu were also observed to be uniformly distributed in the ventral caeca. Pb was not detected in either of these tissues. The apparent normal morphology and the typical number of oocytes undergoing secondary vitellogenesis suggest that vitellogenesis was not being disrupted by Pb displacing Zn in the metal-binding domain of vitellogenin in amphipods exposed to the contaminated sediment during the test. Alternative mechanisms for the reproductive toxicity of amphipods exposed for six days to metal-contaminated sediment are discussed.

Calibration and field application of Chemcatcher® passive samplers for detecting amitrole residues in agricultural drain waters.

A passive sampler device suitable for monitoring of residues of the hydrophilic ionic herbicide amitrole in irrigation waterways was developed. Uptake of amitrole on styrenedivinylbenzene-reverse phase sulfonated Empore™ disks was linear and proportional to its water concentration over the range of 1-10 µg/L with a sampling rate of 23.1 mL/day under laboratory flow-through conditions. Performance of the sampler was evaluated by deployment in an agricultural irrigation drain for 10 days. The amount of amitrole adsorbed by the passive samplers compared well with the cumulative mean water concentrations calculated from daily spot samplings of the drain water.

The ecological effects of a herbicide-insecticide mixture on an experimental freshwater ecosystem.

The effects of a co-occurring insecticide-herbicide mixture were evaluated using model ecosystems (microcosms) in the laboratory. Microcosms dosed with a high concentration (10 µg/L) of the insecticide terbufos, alone and as a mixture with the herbicide atrazine (25 µg/L), exhibited community level effects attributed to the elimination and decline of invertebrate populations, and also indirect effects. There were no community level effects at a lower concentration of terbufos (0.1 µg/L) alone or in a mixture with atrazine, although delayed population effects were observed. Female chironomids also emerged later and those from terbufos-only microcosms were smaller. Exposure to atrazine alone was also associated with lower abundances of cladocerans and reduced emergence of chironomids. The risk posed by atrazine is low and is unlikely to exacerbate the effects of terbufos. Nevertheless, the population-level effects highlight that terbufos poses a potential risk to aquatic ecosystems, regardless of whether atrazine is also present.

Recent developments and applications of electron microscopy to heterogeneous catalysis.

Transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) are popular and powerful techniques used to characterize heterogeneous catalysts. Rapid developments in electron microscopy--especially aberration correctors and in situ methods--permit remarkable capabilities for visualizing both morphologies and atomic and electronic structures. The purpose of this review is to summarize the significant developments and achievements in this field with particular emphasis on the characterization of catalysts. We also highlight the potential and limitations of the various methods, describe the need for synergistic and complementary tools when characterizing heterogeneous catalysts, and conclude with an outlook that also envisions future needs in the field.

Dissecting rapid estrogen signaling with conjugates.

Hypothesizing that rapid estrogen signaling could be modulated from different estrogen receptors with unique localization patterns, a number of groups have attempted to design drug conjugates that target or restrict compounds to specific subcellular compartments. This article will briefly discuss the history of using conjugates to dissect rapid estrogen signaling and different strategies to attempt to target estrogens and antiestrogens to different locations. It will also detail some of the potential issues that can arise with different types of conjugates, using examples drawn from the authors' own work.

Tamoxifen promotes superoxide production in platelets by activation of PI3-kinase and NADPH oxidase pathways.

BACKGROUND: Tamoxifen is a selective estrogen receptor antagonist that is widely used for treatment and prevention of breast cancer. However, tamoxifen use can lead to an increased incidence of thrombotic events. The reason for this adverse event remains unknown. Previous studies showed that tamoxifen and its active metabolite Z-4-hydroxytamoxifen rapidly increased intracellular free calcium ([Ca(2+)](i)) in human platelets by a non-genomic mechanism that involved the activation of phospholipase C. Platelets play a pivotal role in thrombosis and Ca(2+) elevation is a central event in platelet activation. Therefore the mechanism by which tamoxifen activated Ca(2+) entry into platelets was investigated. METHODS: [Ca(2+)](i) was measured using the fluorescent indicator fura-2 and reactive oxygen species were measured using lucigenin in isolated human platelets. RESULTS: Tamoxifen analogs E-4-hydroxytamoxifen, with weak activity at the nuclear estrogen receptor and Z-4-hydroxytamoxifen, with strong activity at nuclear estrogen receptor, were equally active at increasing [Ca(2+)](i) and synergizing with ADP and thrombin to increase [Ca(2+)](i) in platelets. This result suggests that the effects of tamoxifen and E- and Z-4-hydroxytamoxifen to increase [Ca(2+)](i) are not mediated by the classical genomic estrogen receptor. The effects of tamoxifen to increase [Ca(2+)](i) were strongly inhibited by apocynin and apocynin dimer. This suggests that tamoxifen activates NADPH oxidase which leads to superoxide generation and in turn caused an increase in [Ca(2+)](i). Free radical scavengers TEMPO and TEMPOL also inhibited tamoxifen-induced [Ca(2+)](i) elevation. Inhibition of phosphoinositide-3-kinase (PI3-kinase), an upstream effector of NADPH oxidase with wortmannin and LY-294,002 also caused substantial inhibition of tamoxifen-induced elevation of [Ca(2+)](i). CONCLUSION: Tamoxifen increases [Ca(2+)](i) in human platelets by a non-genomic mechanism. Tamoxifen activates phospholipase Cγ as well as PI3-kinase and NADPH oxidase pathway to generate superoxide which causes the release of Ca(2+) from the endoplasmic reticulum, and promotes Ca(2+) influx into the platelets.

Review of the reproductive biology of amphipods and their endocrine regulation: identification of mechanistic pathways for reproductive toxicants.

The reproductive biology of amphipods is reviewed to update the knowledge of the male and female reproductive processes of oogenesis and spermatogenesis as well as the endocrine systems of amphipods with the aim of advancing studies of reproductive toxicology. The ovarian and reproduction cycles of female gammaridean amphipods are closely correlated with the molt cycle, which is under direct control by the steroid hormone 20-hydroxyecdysone. The ability of males to copulate and subsequently for females to ovulate is restricted to the early postmolt period of the females. New developments in our understanding of the molt cycle and the endocrine regulatory pathways for reproduction using genomics techniques on other crustacean species are also discussed. The arthropod sterol ponasterone A or xenobiotics such as the fungicide fenarimol have been shown to elicit endocrine disruption in some crustaceans by acting as an agonist for 20-hydroxyecdysone at the ecdysone receptor or by inhibiting the synthesis of 20-hydroxyecdysone, respectively, resulting in disruption of molting and reproduction. Recent studies suggest that cadmium can inhibit secondary vitellogenesis in amphipods. Experimental approaches for examining the metabolic pathways associated with ecdysteroid hormonal signaling or metabolism, exoskeleton maintenance and molting, and the regulation of vitellogenin in amphipods are discussed. This information should aid in the identification of useful biomarkers for reproductive toxicity.

Developmental toxicity of two common corn pesticides to the endangered southern bell frog (Litoria raniformis).

To examine the link between corn agriculture and the observed decline of the endangered southern bell frog (SBF), the effects of two corn crop pesticides on larval growth and development were investigated. Tadpoles were exposed to terbufos sulfone (10 µg/L), a major breakdown product of the insecticide terbufos, and the herbicide atrazine (25 µg/L) individually and as a mixture until the completion of metamorphosis. Atrazine did not interact synergistically with terbufos sulfone or result in significant effects on growth and development alone, although there was some indication of accelerated metamorphosis in the pilot study. Terbufos sulfone alone and as a mixture (terbufos/atrazine) significantly slowed larval development and ultimately delayed metamorphosis. The observed developmental effects from an environmentally relevant concentration of terbufos sulfone indicates a risk posed by this persistent degradation product to the endangered SBF, which breeds and develops in the rice bays adjacent to corn fields treated with pesticides.

Foraging, feeding, and reproduction on silica substrate: Increased waterborne zinc toxicity to the estuarine epibenthic amphipod Melita plumulosa.

Artificial substrates consisting of fine milled silica with or without α-cellulose were evaluated for their capacity to support survival, growth, and fecundity in the amphipod Melita plumulosa. There were no significant differences in the survival and fecundity of adult amphipods maintained for up to 13 d on natural sediment, silica-only, or silica/α-cellulose substrate when fed two algal foods, Sera micron and Rotiselco-ALG. However, growth among juveniles maintained on the silica/α-cellulose mixture was significantly inhibited over 14 d compared with natural sediment. Addition of a microencapsulated shrimp feed, Frippak, to the algal foods improved juvenile growth over 28 d but still did not match the nutritive value of natural sediment. Fine silica without cellulose was subsequently used in acute and reproductive toxicity tests with waterborne zinc. With food, a 10-d median lethal concentration (LC50) of 140 µg Zn/L and a 10-d no-effect concentration (NEC) of 80 µg Zn/L were obtained for juvenile survival on silica. In contrast, a 10-d LC50 of 200 µg Zn/L and a 10-d NEC of 180 µg Zn/L were obtained for juveniles in water-only exposures. Similarly, exposure of adult females to Zn without food on silica compared with water-only exposures gave 10-d LC50s of 380 and 490 µg Zn/L and 10-d NECs of 130 and 370 µg Zn/L, respectively. The reproduction toxicity test indicated significant adult mortality at 92 µg Zn/L and significantly reduced fecundity at 22 µg Zn/L. We surmised that the toxicity of waterborne zinc to M. plumulosa increased when maintained on nutrient-depleted silica compared with water-only exposure because of increased energy expended through foraging, in concert with the likely increased exposure to Zn via the digestive tract and the gills.

Comparison of environmental risks of pesticides between tropical and nontropical regions.

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.