Individual and mixture toxicity of carbofuran and diuron to the protozoan Paramecium caudatum and the cladoceran Ceriodaphnia silvestrii.

The toxicity of the insecticide carbofuran and herbicide diuron (individually and in mixture) to the invertebrates Paramecium caudatum and Ceriodaphnia silvestrii was evaluated. Acute and chronic toxicity tests were carried out with the diuron and carbofuran active ingredients and their commercial products, Diuron Nortox® 500 SC and Furadan® 350 SC, respectively. Individual toxicity tests showed that C. silvestrii was more sensitive to both carbofuran and diuron than P. caudatum. In single exposures, both pesticides caused adverse effects to C. silvestrii in environmentally relevant concentrations (48 h EC50 = 0.001 mg L-1 and 8 d LOEC = 0.00038 mg L-1 for formulated carbofuran; 8 d LOEC < 0.05 mg L-1 for formulated diuron). For P. caudatum, carbofuran and diuron in single exposures were only slightly toxic (24 h IC50 = 5.1 mg L-1 and 6.9 mg L-1 for formulated carbofuran and diuron, respectively). Acute and chronic exposures to diuron and carbofuran mixtures caused significant deviations of the toxicity predicted by the Concentration Addition and Independent Action reference models for both test species. For the protozoan P. caudatum, a dose-dependent deviation was verified for mortality, with synergism caused mainly by carbofuran and antagonism caused mainly by diuron. For protozoan population growth, however, an antagonistic deviation was observed when the active ingredient mixtures were tested. In the case of C. silvestrii, antagonism at low concentrations and synergism at high concentrations were revealed after acute exposure to active ingredient mixtures, whereas for reproduction an antagonistic deviation was found. Commercial formulation mixtures presented significantly higher toxicity than the active ingredient mixtures. Our results showed that carbofuran and diuron interact and cause different toxic responses than those predicted by the individually tested compounds. Their mixture toxicity should therefore be considered in risk assessments as these pesticides are likely to be present simultaneously in edge-of-field waterbodies.

Effects of parabens on antioxidant system and oxidative damages in Nile tilapia (Oreochromis niloticus).

In this study, effects of parabens on antioxidant defenses and oxidative damages in gills and liver of Nile tilapia (Oreochromis niloticus) were evaluated. Adult Nile tilapia were exposed to methyl, ethyl, propyl, butyl and benzylparaben and a mixture of methyl and propylparaben for 6 and 12 days. The biomarkers analyzed were superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), total glutathione (GSH-t) and lipid peroxidation measured by malondialdehyde (MDA) content. Results indicated that exposure to parabens caused biochemical changes in gill and liver cells, which in turn modulated enzymatic and non-enzymatic antioxidants in Nile tilapia. SOD, GPx and GR activity significantly increased in gills and liver after exposure to most parabens. CAT activity had little (liver) or no alteration (gills) in this fish species after treatment with parabens. GSH-t content in liver decreased after 6 days of exposure to parabens, but after 12 days, GSH-t levels increased in liver in all treatments, indicating an antioxidant adaptation to exposure to sublethal doses of parabens. Regarding the MDA levels, no alterations were observed in gills compared to control and in liver the MDA content was reduced after 12d of exposure to ethylparaben, butylparaben and paraben mixture, indicating no lipid peroxidation in the analyzed tissues. Our results demonstrate parabens-induced adaptive responses in fish, which were important in the protection against oxidative damages.

Acute and chronic toxicity of diuron and carbofuran to the neotropical cladoceran Ceriodaphnia silvestrii.

In order to contribute to the increase of the body of knowledge on the sensitivity of tropical indigenous species to pesticides, acute and chronic toxicity tests were conducted with the neotropical cladoceran Ceriodaphnia silvestrii. Tests were carried out with the active ingredients diuron and carbofuran and one of their commercial formulations, the Diuron Nortox® 500 SC and the Furadan® 350 SC, respectively. For carbofuran, the active ingredient was more toxic than the commercial product, whereas for diuron, the commercial product appeared more toxic. In addition, hormetic effects on fertility were recorded for intermediate diuron concentrations. Acute and chronic toxicity data indicated that C. silvestrii was among the most sensitive invertebrate species for both test compounds. Based on concentrations measured in Brazilian water bodies, these compounds represent ecological risks for causing direct and indirect toxic effects on C. silvestrii and other aquatic organisms. Our results support previous claims on the advantages of using native species to better tune ecological risk assessment of chemicals in tropical ecosystems.

Effects of diuron and carbofuran and their mixtures on the microalgae Raphidocelis subcapitata.

In aquatic environments, organisms are often exposed to mixtures of several pesticides. In this study, the effects of carbofuran and diuron and their mixtures on the microalgae Raphidocelis subcapitata were investigated. For this purpose, toxicity tests were performed with the single compounds (active ingredients and commercial formulations) and their combinations (only active ingredients). According to the results, the toxicity of active ingredients and their commercial formulations to R. subcapitata was similar. In the single exposures, both carbofuran and diuron inhibited significantly the R. subcapitata growth and caused physiological (chlorophyll a content) and morphological (complexity and cell size) changes in cells, as captured by flow cytometry single-cell properties. Regarding the mixture toxicity tests, data fitted to both reference models, concentration addition (CA) and independent action (IA), and evidenced significant deviations. After the CA fitting, dose-ratio dependent deviation had the best fit to the data, demonstrating synergism caused mainly by diuron and antagonism caused mainly by carbofuran. After fitting the IA model, a synergistic deviation represented the best fit for the diuron and carbofuran mixtures. In general, the two reference models indicated the occurrence of synergism in the mixtures of these compounds, especially when diuron was the dominant chemical in the combinations. The increased toxicity caused by the mixture of these pesticides could pose a greater environmental risk for phytoplankton. Thus, exposure to diuron and carbofuran mixtures must also be considered in risk assessments, since the combination of these compounds may result in more severe effects on algae population growth than single exposures.

Influence of PPCPs on the performance of intermittently operated slow sand filters for household water purification.

Removal of pharmaceuticals and personal care products (PPCPs) from drinking water is usually enhanced by advanced oxidation which is not affordable in low income countries. Slow sand filtration has been found to be capable of removing anti-inflammatory compounds, and its low maintenance costs and easy operation make it an attractive technology for treating drinking water in many parts of the world. In addition, slow sand filters can be used at both large and household scales. The biofilm (i.e. schmutzdecke) developed on the top of the sand and within the upper layers of the sand is acknowledged to be responsible for the water purification. However, it is possible that the PPCPs may affect the schmutzdecke development and microbial community within the filters, and consequently the performance of the filter. This study investigated two household slow sand filters (for water purification) operated intermittently with and without contamination by six PPCPs. Eleven parameters were monitored in the affluent and effluent water, including bacterial species present and schmutzdecke biomass development. Results demonstrated that the household slow sand filter performance was not affected by the 2µgL-1 of PPCPs in the water. There was no significant difference between filters for total coliforms and E. coli removal, but there was considerable difference between sampling times. Biomass considerably increased with the number of filtrations in both filters and there was no significant difference between filter biomass. However, it was found that more bacterial species were present in the period with no contamination than during the contamination period. Bacillus anthracis and Exiguobacterium sp. showed to be resistant to the effects of the PPCPs. These suggest there are effects of PPCPs on bacterial species within the filter. However, the effect of the PPCPs on biomass was not conclusive in this study and needs to be further investigated.

Effects of diuron and carbofuran pesticides in their pure and commercial forms on Paramecium caudatum: The use of protozoan in ecotoxicology.

Toxic effects of diuron and carbofuran on Paramecium caudatum were evaluated. Acute and chronic tests were conducted with diuron and carbofuran active ingredients and their commercial formulations, Diuron Nortox(®) 500 SC and Furadan(®) 350 SC, respectively. The sensitivity range of P. caudatum to reference substance sodium chloride was established. A preliminary risk assessment of diuron and carbofuran for Brazilian water bodies was performed. The tests indicated that toxicity of pure diuron and its commercial formulation was similar, while the commercial product carbofuran was more toxic than its pure form. In acute tests, readings were carried out at 2, 3, 4 and 6 h and showed an increase of mortality with increasing exposure time. The sensitivity of P. caudatum to NaCl ranged from 3.31 to 4.44 g L(-1), averaging 3.88 g L(-1). For diuron, the 6 h LC50 was 64.6 ± 3.3 mg L(-1) for its pure form and 62.4 ± 2.5 mg L(-1) for its commercial formulation. Carbofuran active ingredient was less toxic than that of diuron, presenting a 6 h LC50 of 142.0 ± 2.4 mg L(-1) for its pure form and 70.4 ± 2.2 mg L(-1) for its commercial product. Chronic tests showed that these pesticides cause significant decrease on population growth, generation number and biomass of P. caudatum. The 24 h IC50 was 7.10 ± 0.58 mg L(-1) for pure diuron, 6.78 ± 0.92 mg L(-1) for commercial diuron, 22.95 ± 3.57 mg L(-1) for pure carbofuran and 4.98 ± 0.62 mg L(-1) for commercial carbofuran. Preliminary risk assessment indicated that diuron and carbofuran present potential ecological risks for Brazilian water bodies. P. caudatum was a suitable and sensitive test organism to evaluate diuron and carbofuran toxicity to freshwater protozooplankton and, taking into account the relevant role of protozoans in aquatic environments, we strongly recommend its inclusion in ecotoxicological studies.

Influência das características das substâncias húmicas na eficiência da coagulação com sulfato de alumínio / The influence of humic substances characteristics on the coagulation efficiency using aluminum sulfate

Neste trabalho foi estudada a influência das características das substâncias húmicas (SH), em especial a massa molar das moléculas, na eficiência da coagulação com o uso do sulfato de alumínio. Utilizando-se de água proveniente de poço profundo, foram preparadas quatro águas de estudo, todas com cor verdadeira de aproximadamente 100 uH. As SH foram extraídas de turfa e fracionadas em massas molares: i) SH filtradas em membranas de 0,45 æm; ii) SH filtradas em membranas de 0,45 æm e maiores que 100 kDa, iii) SH com moléculas entre 30 e 100 kDa; iv) SH com moléculas menores do que 30 kDa. Verificou-se que quanto maior a massa molar das SH maior foi a eficiência de remoção da cor aparente, com as menores dosagens de coagulante.O pH de coagulação ótimo, esteve entre 6,0 e 7,0, para todas as águas de estudo. Os estudos da porcentagem de ácido húmico (AH) e ácido fúlvico (AF) presentes em cada fração de diferente massa molar mostraram que quanto maior foi à porcentagem de AF presente, maior foi à dosagem de coagulante exigida para se obter os melhores resultados de remoção da cor aparente.