Contamination and persistence of polycyclic aromatic hydrocarbons (PAHs) in rice grains after drying in direct-fired dryer.

The objective of this work was to study PAHs contamination in rice grains subjected to different milling types, after drying at different air temperatures in a direct-fired dryer and using firewood with different moisture contents as a heating source. In addition to verifying the persistence of these compounds after storage. Drying of rice grains was performed in a cross-flow dryer at air temperatures of 55 and 65 ºC. As heating source firewood containing different moisture contents was used. The presence of nine PAHs was detected. The drying air temperature, as well as the storage time, did not significantly influence the PAHs contamination of grains. The highest PAHs contamination was observed in grains from the brown subgroup. Grain polishing promoted a reduction in the PAH concentration. The grains subjected to parboilization showed a higher PAHs concentration. The use of firewood with higher moisture content promoted greater PAHs contamination in the grains.

Role of climatic factors in the toxicity of fipronil toward earthworms in two tropical soils: effects of increased temperature and reduced soil moisture content.

The aim of this study was to assess the effect of temperature on the toxicity of fipronil toward earthworms (Eisenia andrei) in two Brazilian soils (Entisol and Oxisol) with contrasting textures. In the case of Entisol, the influence of soil moisture content on toxicity was also investigated. Earthworms were exposed for 56 days to soils spiked with increasing concentrations of fipronil (8.95, 19.48, 38.22, 155.61, and 237.81 mg kg-1 for Entisol; 12.99, 27.94, 48.42, 204.67, and 374.29 mg kg-1 for Oxisol) under scenarios with different combinations of temperature (20, 25 and 27 °C) and soil moisture content (60 and 30% of water holding capacity (WHC) for Entisol and 60% WHC for Oxisol). The number of juveniles produced was taken as the endpoint, and a risk assessment was performed based on the hazard quotient (HQ). In Entisol, at 60% WHC the fipronil toxicity decreased at 27 °C compared with the other temperatures tested (EC50 = 52.58, 48.48, and 110 mg kg-1 for 20, 25, and 27 °C, respectively). In the case of Oxisol at 60% WHC, the fipronil toxicity increased at 27 °C compared with other temperatures (EC50 = 277.57, 312.87, and 39.89 mg kg-1 at 20, 25, and 27 °C, respectively). An increase in fipronil toxicity was also observed with a decrease in soil moisture content in Entisol at 27 °C (EC50 = 27.95 and 110 mg kg-1 for 30% and 60% WHC, respectively). The risk of fipronil was only significant at 27 °C in Entisol and Oxisol with water contents of 30% and 60% WHC, respectively, revealing that higher temperatures are able to increase the risk of fipronil toxicity toward earthworms depending on soil type and soil moisture content. The results reported herein show that soil properties associated with climatic shifts could enhance the ecotoxicological effects and risk of fipronil for earthworms, depending on the type of soil.

Can the increase in atmospheric temperature enhance the toxicity and risk of fipronil for collembolans in tropical soils?

We evaluated the toxicity and risk (via toxicity exposure ratio approach - TER) of the insecticide fipronil to collembolan's growth and reproduction in three tropical soils, under increasing atmospheric temperatures. Chronic toxicity tests were performed with Folsomia candida in tropical artificial soil (TAS), oxisol, and entisol spiked with increasing concentrations of fipronil, at three room temperature scenarios: a standard (20 ± 2 °C), a tropical condition (25 ± 2 °C) and a global warming simulation (27 ± 2 °C). Temperatures influenced the fipronil effects on the species reproduction differently between soil types. In TAS and oxisol the highest toxicities (EC50-based) were found at 27 °C (EC50 TAS = 0.81, 0.70, 0.31 mg kg-1; EC50 OXISOL = 0.52, 0.54, 0.40 mg kg-1; at 20, 25, and 27 °C, respectively). In entisol, the toxicity at 27 °C was lower compared to 25 and 20 °C (EC50 ENTISOL = 0.33, 0.24, 0.12 mg kg-1, respectively). Fipronil concentrations also increased the proportion of small juveniles (growth reduction) in all tested soils. However, this effect was greater (EC10-based) at higher temperatures (25 and/or 27 °C), regardless of the soil type. TER approach revealed a significant risk of fipronil in entisol, regardless of the tested temperature, while in other soils the risk was found significant only at the higher temperatures (25 and 27 °C for TAS, and 27 °C for oxisol). These results indicate that exposures to fipronil at high temperatures (e.g., those resulting from climate change) can threaten F. candida populations, depending on the soil type.

Toxicity of fipronil to Folsomia candida in contrasting tropical soils and soil moisture contents: effects on the reproduction and growth.

This study assessed the influence of three tropical soil types and soil moisture content on the toxicity and risk of the insecticide fipronil to collembolans Folsomia candida. Chronic toxicity tests were performed in a Tropical Artificial Soil (TAS), an Oxisol and an Entisol spiked with increasing concentrations of fipronil to assess the effects on the reproduction and growth of the species. The soil moisture contents were kept at 60% (standard condition) and 30 or 45% (water restriction) of their water holding capacity (WHC). The toxicity of fipronil on collembolans reproduction was about three times higher in Entisol compared to TAS or Oxisol. Higher toxicities were also found in the drier TAS (EC50 30%WHC = 0.20 vs EC50 60%WHC = 0.70 mg kg-1) and Oxisol (EC50 45%WHC = 0.27 vs EC50 60%WHC = 0.54 mg kg-1), while in Entisol lower impacts were found in the drier samples (EC50 30%WHC = 0.41 vs EC50 60%WHC = 0.24 mg kg-1). For all tested soils, the size of generated collembolans was reduced by the fipronil concentrations, regardless of soil moisture. However, the drier condition increased the effect on the growth in TAS and Entisol for some concentrations. A significant risk of exposure was found in TAS and Oxisol at drier conditions and, for Entisol, regardless of the soil moisture. The toxic effects and risk of fipronil on collembolans were higher in the natural sandy soil. The soil moisture content increase or decrease the toxicity of the insecticide for collembolans, depending on soil type.