[Development of Analytical Method and Surveillance ofGibberellic Acid in Banana, Cherry, and Kiwi Fruit].

Gibberellic acid (GA3) is commonly used as a plant growth regulator in many food crops owing to its essential signaling functions during plant growth and development. In Japan, a threshold for administrative action for GA3 content of 0.3 mg/kg applies in produce in which maximum residue limits have not been established. Although the threshold is based on previous studies, the GA3 concentrations in individual foods are still unknown. Thus, we surveyed the concentrations of GA3 in banana, cherry, and kiwi fruit on the Japanese market. We developed and validated a method for the analysis of GA3 using solid-phase extraction and LC-MS/MS in accordance with accepted criteria of trueness, repeatability, and selectivity. The limits of detection and of quantification were determined as 0.005 and 0.05 mg/kg, respectively, in all fruits. Concentrations of GA3 did not exceed 0.3 mg/kg regardless of ripeness, suggesting the reasonability of the current regulation of GA3 in banana, cherry, and kiwi fruit. These findings can support prompt administrative action on these fruits, contributing to the regulation of GA3 in Japan.

[Estimation of the Distribution of Dietary Exposure to Lead Using Two-Dimensional Monte Carlo Simulation: An Attempt to Apply to Total Diet Samples].

The average dietary exposure to lead (Pb) in male and female Japanese individuals >1 year of age was estimated using 280 total diet samples representing 14 food groups from 10 areas over a two-year period. A probabilistic exposure estimation was performed using a two-dimensional Monte Carlo simulation (2D-MCS) with a Bayesian estimation that consided the uncertainty of the estimation process. The Bayesian estimation was performed using the likelihood function with cumulative distribution function between the lower and upper boundary values for no-detected values. The median dietary exposure to Pb was estimated as 5.82 µg/person/day. The 90% interval was 2.51-16.9 µg/person/day. Comparison with previously reported Pb exposure values indicates that the estimation of Pb exposure distribution using total diet samples is reasonable. The contribution to Pb exposure was highest in the order of food group 8 (light-colored vegetables, mushrooms, and seaweeds: 20.0±16.1%)>food group 1 (rice and rice products: 12.3±19.0%)>food group 10 (fish and shellfish: 10.5±13.9%). Owing to the high uncertainties of contribution ratios, it was not possible to identify dominant food groups contributing to Pb exposure. However, it was evident that the uncertainty of the estimation of Pb exposure was influenced by the uncertainty of Pb concentration than the uncertainty of food consumption rate. In particular, the effect of uncertainty from the Pb concentration of the food group 1 was 68.2%. When the margin of exposures were calculated, the estimated probabilities that a value would be <1 were 14.5% for developmental neurotoxicity to children (1-6 years old), 0.13% for blood pressure and 0.93% for kidney disease in Japanese individuals ≥1 year of age. The findings suggest that the health risk due to dietary Pb exposure is small but not negligible.

Quantification of progesterone in beef with marbling using liquid chromatography-tandem mass spectrometry with stable isotope-labelled standards.

Progesterone (P4) is contained naturally in animal tissue, and it is also used as a veterinary drug in cattle for treatment purposes. To assess the risk from P4 residues in beef derived from treated cattle, it is essential to quantify the P4 contained naturally in cattle tissue (endogenous P4). Therefore, we performed a method validation for the quantification of endogenous P4 (method quantification limit = 0.06 ng g-1) by using isotope-labelled P4s, and investigated the P4 contents in Japanese beef (n= 112; 0.07 to 121 ng g-1). The P4 contents in cattle muscle ranged from 0.07 to 54.3 ng g-1 in males, and from 0.27 to 121 ng g-1 in females. Our investigation also indicated that the developed method using both 13C- and deuterium-labelled P4 standards could be used to certify the recovery of P4 from cattle muscle containing various amounts of intramuscular fat, and enabled the determination of the P4 content in all Japanese beef samples that exceeded the method quantification limit.

Behavior of isoprothiolane and fipronil in paddy water, soil, and rice plants after nursery-box or submerged applications.

We investigated the behavior of isoprothiolane and fipronil after nursery-box application and that of isoprothiolane after submerged application in an experimental paddy field. The concentrations of the pesticides and their metabolites were monitored in paddy water, soil, and rice plants. The distribution profile for isoprothiolane mass in the field differed greatly between the nursery-box and submerged applications. The nursery-box-applied pesticides were mostly distributed in soil near the transplanted rice seedlings (root zone), versus little distribution in paddy water and rice plants (<1.1 and <0.3% of the applied mass, respectively). The residual levels in rice plants were similar to those in the root-zone soil. To estimate the soil pesticide mass, we defined a key parameter: the ratio of the root-zone area to the total area of the paddy field estimated to be 0.1 to 0.15. This parameter is important when evaluating the concentrations of nursery-box-applied pesticides in soil and rice plants.

Improved PADDY-Large model including lateral seepage loss from paddy fields to predict pesticide behavior in river basins.

We developed an improved simulation model for predicting pesticide concentrations in river basins based on PADDY-Large, which includes lateral seepage loss of pesticides from paddy fields. Based on the structure of typical Japanese paddy fields, pesticide transport process due to lateral seepage through bunds was modeled as a compartment system consisting of pore water and soil particle. The model was validated with concentrations measured by monitoring paddy pesticides in a tributary of the Sakura River in Japan. The improved model by including loss of pesticides due to lateral seepage through bunds successfully simulated temporal changes in the pesticide concentrations.