Fate of 14C-ethion insecticide in the presence of deltamethrin and dimilin pesticides in cotton seeds and oils, removal of ethion residues in oils, and bioavailability of its bound residues to experimental animals

Estimation of chronic dietary intake of pesticide residues

OBJECTIVE

To estimate the maximum theoretical daily intake of pesticides potentially consumed, chronically, by the Brazilian population.

METHOD

By using data from the food consumption section of the 2008-2009 Household Budget Survey to characterize the population diet, a database was built to group the foods based on the NOVA classification. Considering the maximum residue limit values of each pesticide authorized in the country until 2016, the limits of all consumed foods were added and multiplied by the amount consumed, resulting in the maximum theoretical intake index, which was compared with the acceptable daily intake.

RESULTS

The results show that, of the 283 pesticides considered in the database, 71 (25%) compounds had estimates of zero intake, 144 compounds (50.8%) reached acceptable daily intake values and 68 compounds (24%) showed median intake that exceeded the acceptable daily value. The pesticide intake estimation according to the different regions of the country showed a variation in the amount of compounds that exceeded the acceptable daily intake (48 to 69 substances) due to the different consumption patterns. The categories of products that most exceeded the limits were the insecticides, herbicides and fungicides.

CONCLUSION

The application of this methodology is valid for the first step in risk assessment, but the resulting values may be different from the actual exposure since they do not include other factors, such as the combined use of pesticides or unauthorized products. The importance of developing research on specific national food consumption data in a systematic way is emphasized, which generates data and analyses that allow a detailed risk assessment.

Thiamethoxam Metabolism and Metabolic Effects in Cell Suspension Culture of Tea ( Camellia sinensis L.)

Thiamethoxam (TMX) has already been proven to have a physiological effect in plant tissue or cell expect for the insecticidal activity. In our previous study, TMX was verified to be metabolized by tea cells in either a suspension culture or tea plant into several metabolites. Here, tea cell suspension cultures were treated for 45 days to investigate the metabolite effects in both the tea cells and the culture supernatants by nontargeted metabolomics. Using multivariate analysis (PCA and OPLS-DA), all treatment and control groups could be clearly separated. Inside the cells, 113 metabolites were found to be up-regulated while 122 were down-regulated, when compared with untreated cells. In the culture supernatant, there were 128 up-regulated and 35 down-regulated metabolites, compared to untreated cultures. KEGG searches revealed that the alanine, aspartate, and glutamate metabolic pathways were strongly affected by TMX metabolism within the tea cell. Molecular docking models showed that (i) 4-aminobutyrate aminotransferase may be related to the formation of 2-chloro-thiazole-5-carboxylic acid and (ii) 3'(2'),5'-bisphosphate nucleotidase may be able to interact with TMX. This study can help us to understand the interaction mechanism of pesticides with plant cells.

Comparison of the Metabolic Behaviors of Six Systemic Insecticides in a Newly Established Cell Suspension Culture Derived from Tea ( Camellia sinensis L.) Leaves

The use of an in vitro cell suspension to study insecticide metabolism is a simpler strategy compared to using intact plants, especially for a difficult matrix such as tea. In this study, a sterile tea leaf callus was inoculated into B₅ liquid media with 2,4-dichlorophenoxyacetic acid (2,4-D, 1.0 mg L^-1) and Kinetin (KT, 0.1 mg L^-1). After 3-4 subcultures (28 days each), a good cell suspension was established. Utilizing these cultures, the metabolic behaviors of six insecticides, including two organophosphates (dimethoate, omethoate) and four neonicotinoids (thiamethoxam, imidacloprid, acetamiprid, and imidaclothiz) were compared. The results showed that thiamethoxam, dimethoate, and omethoate were easily metabolized by tea cells, with degradation ratios after 75 days of 55.3%, 90.4%, and 100%, respectively. Seven metabolites of thiamethoxan and two metabolites of dimethoate were found in treated cell cultures using mass-spectrometry, compared to only two metabolites for thiamethoxam and one for dimethoate in treated intact plants.