RESUMO
Tropical regions' economy is usually based on agriculture, which involves an intensive use, and even frequent overuse, of pesticides. Nevertheless, not much research has been done on the impact of pesticides on tropical aquatic ecosystems, which are often contaminated by runoff-related pesticide inputs due to unpredictable and torrential rainfalls. This study aimed to: (i) adapt and evaluate a short-term sublethal in situ assay using post-exposure feeding as an endpoint, to the tropical cladoceran species Diaphanosoma brachyurum (collected at the Pedra do Cavalo dam in the Paraguaçu River basin, Bahia, Brazil), and, (ii) assess the role of the standard species Daphnia magna as an adequate laboratory surrogate. Lethal and sublethal (post-exposure feeding) responses were assessed for the two species. To evaluate these responses under environmentally realistic exposure conditions, a runoff event was simulated in an agricultural area previously contaminated with different deltamethrin concentrations. The resultant runoff water was used to set up microcosms with different dilutions, simulating the entrance of runoff water in an adjacent lentic system. An in situ assay with D. brachyurum was performed inside the microcosms, allowing to discriminate the effects due to deltamethrin from those due to other potential stressors associated with the experimental design (e.g. organism handling, load of suspended particles, microcosm design). Water samples were collected from microcosms to conduct a laboratory assay with D. magna. The in situ methodologies revealed to be suitable to conduct assays with D. brachyurum under tropical conditions, since all exposed organisms were successfully retrieved from the chambers. Furthermore, none of the potential stressors associated with the experimental design influenced the daphnids' performance. The tropical cladoceran species, exposed under more realistic conditions, revealed to be more sensitive than the laboratory standard species: lethal effects were only observed for D. brachyurum and sublethal effects were noticed at a lower deltamethrin concentration for this species than for D. magna.
Assuntos
Agricultura , Crustáceos/metabolismo , Resíduos Industriais/análise , Praguicidas/toxicidade , Animais , Brasil , Daphnia/metabolismo , Interpretação Estatística de Dados , Comportamento Alimentar/efeitos dos fármacos , Inseticidas/toxicidade , Nitrilas/toxicidade , Praguicidas/análise , Piretrinas/toxicidade , Clima Tropical , Poluição da Água/efeitos adversosRESUMO
Water quality and the contamination in relation to land use in the fluvial-lagoon system of the Palizada River (FLSPR; State of Campeche, Mexico) was investigated using an integrated approach including 21-d in situ bioassays with the native mosquito fish Gambusia yucatana, determination of cholinesterase (ChE) activity in wild populations of this species, and water-quality variables. The present study was performed over 19 months at three sites with different types of anthropogenic impact. Significant differences in a water-quality index for aquatic life (WQI) were found among sites. Fish mortality was significantly and negatively correlated with WQI, dissolved oxygen, and sulfates. High survival rates (> or =80%) were found in preliminary exposures and in some of the bioassays performed at all sites. Therefore, test chambers and the cabinet seemed to be suitable for use in toxicity bioassays with G. yucatana. The in situ bioassay was able to discriminate levels of water contamination in both time and space, indicating that it is suitable for use in conditions similar to those found in the FLSPR. In the biomonitoring study, a ChE inhibition of greater than 20% in wild fish was found in some periods of the year at all sampling sites. This indicates the presence of anticholinesterase agents in the water. Fish from two of the sites had a ChE inhibition of greater than 40% in some sampling months, suggesting that deleterious effects already may have been induced in fish. Furthermore, at these sites, the pattern of ChE inhibition was in good agreement with the probable runoff of pesticides from agricultural fields.
Assuntos
Colinesterases/metabolismo , Ciprinodontiformes/metabolismo , Monitoramento Ambiental/métodos , Poluentes Químicos da Água/análise , Agricultura , Animais , Feminino , Cabeça , Masculino , México , Músculos/enzimologia , Nitratos/análise , Praguicidas , Compostos de Amônio Quaternário/análise , Rios , Análise de Sobrevida , Eliminação de Resíduos Líquidos , Poluentes Químicos da Água/toxicidadeRESUMO
Rice is the main crop in the subbasin of the fluvial lagoon system of Palizada River (FLSPR) in the state of Campeche, Mexico. The pesticides used to control pests of this crop mainly are carbofuran, chlorpyrifos, and glyphosate. Black-bellied whistling duck (Dendrocygna autumnalis) is an ecologically and economically important species in the area. This duck is consumed by local inhabitants throughout the year, despite its potential exposure to pesticides. Due to its feeding habits, abundance, and nutritional value, D. autumnalis is a good indicator of environmental contamination and a potential route of human exposure to organophosphate and carbamate pesticides. In this study, the brain cholinesterase (ChE) in the frontal cerebral cortex of autochthonous ducks was characterized. In addition, the potential of the three locally used pesticides and mixtures to inhibit ChE activity was investigated and the exposure of the wild duck population during intensive pesticide applications in rice fields was evaluated. We found that acetylcholinesterase (AChE) seems to be the predominant ChE form in the biological fraction analyzed. Carbofuran was the most potent ChE inhibitor of D. autumnalis brain ChE activity from the three pesticides analyzed. Cholinesterase inhibition after exposure to pesticide mixtures predominantly was due to carbofuran. A decrease (p < 0.05) in AChE activity (>30%) was apparent in wild ducks compared to reference ducks, with recovery of ChE inhibition in wild ducks occurring months later when no pesticides were applied in the field. Dendrocygna autumnalis brain ChE is a suitable parameter for inclusion in biomonitoring programs for both environmental protection and human safety.
Assuntos
Córtex Cerebral/enzimologia , Inibidores da Colinesterase/toxicidade , Colinesterases/metabolismo , Exposição Ambiental , Poluentes Químicos da Água/toxicidade , Acetilcolinesterase/sangue , Acetilcolinesterase/metabolismo , Ração Animal , Animais , Carbamatos/toxicidade , Carbofurano/sangue , Carbofurano/metabolismo , Inibidores da Colinesterase/sangue , Inibidores da Colinesterase/metabolismo , Colinesterases/sangue , Patos , Humanos , México , Organofosfatos/toxicidade , Praguicidas/toxicidadeRESUMO
The authors surveyed agricultural production methods and pesticide use among subsistence farmers (campesinos) in 4 rural communities of Campeche, Mexico. Self-reports of symptoms of poisoning resulting from occupational pesticide exposure were elicited by questionnaire (N = 121), and acetylcholinesterase (AChE) activity during insecticide use was evaluated from blood samples (N = 127). In individuals from 2 of the 4 communities, AChE activity was significantly lower (p < 0.05) than the mean of activity determined for individuals in a reference group. Results of this study show that erythrocyte AChE inhibition provides a good biomarker of exposure to organophosphate pesticides in field studies with human populations. Carbamates, particularly carbofuran, seem to be more associated with exuberant and diversified symptomatology of pesticide exposure than organophosphates. Studies in field communities where both carbamates and organophosphates are suspected to exist should include blood AChE determinations, symptomatology surveys, and socioeconomic questionnaires. The authors recommend that the Mexican National Health Ministry authorities specify additional provisions regarding the use of protective equipment and the adoption of other safety practices during field work, increase information campaigns about the risks of pesticide use and the value of safety practices, and increase programs of medical monitoring and assistance for rural communities dealing with pesticides.