RESUMO
The practice of intensive herbicide use in the sugarcane industry has a high risk of compromising the quality of the water and the organisms that live there due to losses through runoff, leaching and other processes. In this work, the dynamics of four herbicides present in three different mixtures were evaluated through their incorporation and elimination in the muscle tissue of tilapia (Oreochromis niloticus). The highest mean values of bioconcentration factors were 1.730 for ametryn, 0.891 for tebuthiuron, 0.322 for hexazinone and 4.783 for diuron. Diuron presented the highest risk regarding the consumption of tilapia fillets by the population. However, considering that the fish would reach maximum levels of diuron when exposed to extremely high concentrations, an individual weighing 70 kg would need to ingest approximately 1.5 kg of this food product to surpass the acceptable daily intake of 0.007 mg kg-1 body weight. It was concluded that the risk of injury to the population consuming tilapia fillets from fish exposed to herbicides in water arising from sugarcane activities is very low. According to the risk estimation performed in this work, which is substantiated by the assumptions of the World Health Organization and the International Life Sciences Institute, there is a low risk of injury to the population consuming tilapia fillets from fish exposed to water containing herbicides in concentrations arising from sugarcane activities. However, as the risk was estimated from laboratory conditions, caution should be taken where herbicide applications are carried out with high frequency near water bodies, as the consumption of fish from these areas is quite common.
RESUMO
Ametryn (AMT) is one of the most widely used herbicides in tropical sugarcane crops, the main culture of São Paulo State, Brazil. It is known as a diffuse pollutant, being found in surface water and sediment of water bodies adjacent to the crop fields. In the present study, the toxicity of AMT to zebrafish (Danio rerio) embryos was evaluated using developmental and biochemical endpoints. At the biochemical level, lactate dehydrogenase responded at the lowest concentration tested (4 µg L-1) indicating a high demand of energy required to cope with the stress condition. Antioxidant enzyme levels were changed at intermediate/high concentrations while oxidative damage (lipid peroxidation) was observed at the last concentration tested (10 mg L-1). This suggests that, like for other herbicides from the triazine group, oxidative stress is a major pathway of toxicity for AMT. Several developmental effects such as oedemas and tail deformities were also observed. The 96 h-EC50 values calculated for different developmental parameters were between 17 and 29 mg L-1. AMT also affected hatching (96 h-EC50 = 22.5 mg L-1) and positioning in the water column (96 h-EC50 = 13.2 mg L-1). In a previous work of the group, lethal toxicity of AMT showed to be much higher to adults than to embryos. However, in the present work, sublethal endpoints assessed suggest that important effects are observed at lower concentrations, improving the sensitivity of the embryo test. Moreover, in this work, sublethal effects were observed for concentrations in the same range as the ones found in the environment, and thus, given that this chemical is widely used in tropical fields, a refined evaluation of risk should be performed based on the monitoring of sublethal and long-term parameters and considering mixture scenarios.
