Ecotoxicity studies of two atrazine nanoformulations: From the evaluation of stability in media to the effects on aquatic organisms.

In the field of agriculture, nanopesticides have been developed as an alternative to the conventional pesticides, being more efficient for pest control. However, before their widespread application it is essential to evaluate their safe application and no environmental impacts. In this paper, we evaluated the toxicological effects of two kinds of atrazine nanoformulations (ATZ NPs) in different biological models (Raphidocelis subcapitata, Danio rerio, Lemna minor, Artemia salina, Lactuca sativa and Daphnia magna) and compared the results with nanoparticle stability over time and the presence of natural organic matter (NOM). The systems showed different characteristics for Zein (ATZ NPZ) (184 ± 2 nm with a PDI of 0.28 ± 0.04 and zeta potential of (30.4 ± 0.05 mV) and poly(epsilon-caprolactone (ATZ PCL) (192 ± 3 nm, polydispersity (PDI) of 0.28 ± 0.28 and zeta potential of -18.8 ± 1.2 mV) nanoparticles. The results showed that there is a correlation between nanoparticles stability and the presence of NOM in the medium and Environmental Concentrations (EC) values. The stability loss or an increase in nanoparticle size result in low toxicity for R. subcapitata and L. minor. For D. magna and D. rerio, the presence of NOM in the medium reduces the ecotoxic effects for ATZ NPZ nanoparticles, but not for ATZ NPs, showing that the nanoparticles characteristics and their interaction with NOM can modulate toxic effects. Nanoparticle stability throughout the evaluation must be considered and become an integral part of toxicity protocol guidelines for nanopesticides, to ensure test quality and authentic results regarding nanopesticide effects in target and non-target organisms.

Chitosan nanoparticles containing the insecticide dimethoate: A new approach in the reduction of harmful ecotoxicological effects.

Organophosphate insecticides such as dimethoate (DMT) are widely used in agriculture. As a side effect, however, these insecticides contaminate bodies of water, resulting in damage to aquatic organisms. The development of nanopesticides may be an innovative alternative in the control of agricultural pests, increasing effectiveness and reducing their toxicological effects. Based upon this, the present study has investigated encapsulated DMT in alginate chitosan nanoparticles (nanoDMT) and evaluated its toxicological effects on non-target organisms. The nanoparticles were characterized by DLS, NTA and AFM, as well as being evaluated by the release profile. Nanoparticle toxicity was also evaluated in comparison with DMT, empty nanoparticles and DMT (NP + DMT), and commercial formulations (cDMT), in the embryos and larvae of Danio rerio (zebrafish) according to lethality, morphology, and behavior. The nanoparticle control (NP) showed hydrodynamic size values of 283 ± 4 nm, a PDI of 0.5 ± 0.05 and a zeta potential of -31 ± 0.4 mV. For nanoparticles containing dimethoate, the nanoparticles showed 301 ± 7 nm size values, a PDI of 0.45 ± 0.02, a zeta potential of -27.9 ± 0.2 mV, and an encapsulation of 75 ± 0.32%, with slow-release overtime (52% after 48 h). The AFM images showed that both types of nanoparticles showed spherical morphology. Major toxic effects on embryo larval development were observed in commercial dimethoate exposure followed by the technical pesticide, predominantly in the highest tested concentrations. With regard to the toxic effects of sodium alginate/chitosan, although there was an increase for LC50-96 h concerning the technical dimethoate, the behavior of the larvae was not affected. The data obtained demonstrate that nanoencapsulated dimethoate reduces the toxicity of insecticides on zebrafish larvae, suggesting that nanoencapsulation may be safer for non-target species, by eliminating collateral effects and thus promoting sustainable agriculture.

Exploring the mechanisms of graphene oxide behavioral and morphological changes in zebrafish.

The presence of natural organic matter such as humic acid (HA) can influence the behavior of graphene oxide (GO) in the aquatic environment. In this study, zebrafish embryos were analyzed after 5 and 7 days of exposure to GO (100 mg L-1) and HA (20 mg L-1) alone or together. The results indicated that, regardless of the presence of HA, larvae exposed to GO for 5 days showed an increase in locomotor activity, reduction in the yolk sac size, and total length and inhibition of AChE activity, but there was no difference in enzyme expression. The statistical analysis indicated that the reductions in total larval length, yolk sac size, and AChE activity in larvae exposed to GO persisted in relation to the control group, but there was a recovery of these parameters in groups also exposed to HA. Larvae exposed to GO for 7 days did not show significant differences in locomotor activity, but the RT-PCR gene expression analysis evidenced an increase in the AChE expression. Since the embryos exposed to GO showed a reduction in overall length, they were submitted to confocal microscopy and their muscle tissue configuration investigated. No changes were observed in the muscle tissue. The results indicated that HA is associated with the toxicity risk modulation by GO and that some compensatory homeostasis mechanisms may be involved in the developmental effects observed in zebrafish.

Insecticide distribution model in human tissues viewing worker's health monitoring programs

This work aimed at evaluating the characteristics of thirty nine insecticides on tissue distribution and accumulation, using their physico-chemical characteristics and the tissues lipid contents to calculate the compounds distribution among the tissues. The insecticides evaluated were selected among those registered in Brazil for agriculture use. The level I fugacity model was used for the calculations of insecticide distribution among the tissues of muscles, viscera, skin, fat, blood, liver, kidneys and gut. The octanol-water partition coefficient, water solubility and tissue lipid contents showed an insecticide distribution in human tissues. Cluster analysis was performed aiming the identification and separation of insecticides groups based on their physico-chemical characteristics as compounds with similar distribution within tissues and at the same time tissues with similar distribution of various insecticides. Cluster analysis pointed out three insecticide groups: in the first, 70 - 86 percent of insecticide accumulation was found in lipid tissues; in the second, 44 - 58 percent; and in the third, 9 -19 percent. These results could contribute to health monitoring programs of farmworkers.

O objetivo desse trabalho foi avaliar as características de 39 inseticidas quanto a sua distribuição e acumulação em tecidos humanos como também avaliar o grau de similaridade entre os inseticidas quanto a sua distribuição nos tecidos. Para tanto, foram utilizadas as características físico-químicas dos compostos e o conteúdo de lipídeos teciduais para calcular a distribuição dos inseticidas entre os tecidos estudados. Os inseticidas selecionados para o presente trabalho foram alguns daqueles que se encontram registrados no Brasil para uso agrícola. No cálculo da distribuição dos inseticidas entre os tecidos foi utilizado o modelo de fugacidade nível I em músculos, vísceras, pele, gordura, sangue, fígado, rins e intestinos. As características físico- químicas dos inseticidas e os conteúdos de lipídio dos tecidos foram usados para calcular a distribuição dos inseticidas entre os tecidos. O coeficiente de partição octanol-água, a solubilidade em água e o conteúdo de lipídio dos tecidos determinaram a distribuição de um inseticida entre tecidos humanos. Foram realizadas análises de agrupamento, para identificar grupos de inseticidas com distribuição similar nos tecidos. 90 por cento dos 39 inseticidas apresentaram distribuição em gordura maior do que 50 por cento. A análise de agrupamento indicou três grupos de inseticidas: no primeiro o percentual acumulado na gordura variou de 70 - 86 por cento, no segundo de 44 - 58 por cento e no terceiro de 9 - 19 por cento. Os resultados obtidos podem contribuir para os programas de monitoramento da saúde do trabalhador rural.