Akiko Kimata

Urinary excretion of 3-phenoxybenzoic acid in middle-aged and elderly general population of Japan

Limited data are available on the background levels of exposure to synthetic pyrethroid (PYR) in Japan, despite their frequent application for agriculture and indoor extermination and possible effects of chronic and/or low-dose PYR exposure on human health. This study was conducted to describe the level and distribution of one of the major PYR metabolites, 3-phenoxybenzoic acid (3-PBA), in urine samples collected from a general population in Japan. The subjects were 535 individuals (184 men and 351 women; 61.5+/-9.8 years of age, mean+/-S.D.) residing in a town in Hokkaido, a dairy and agricultural area. Urinary 3-PBA was found detectable in 98% of samples above the limit of detection of 0.02 microg/l. The geometric mean values of urinary 3-PBA in occupationally exposed farmers (n=87) and the remaining general group without occupational exposure (n=448) were 0.38 and 0.29 microg/l, respectively, ranging from <LOD to 17.09 microg/l. No significant differences in urinary 3-PBA concentrations were shown between these two groups. Moreover, 3-PBA concentrations were found comparable to those reported in some countries. The present study is, to our knowledge, the first report of a biological monitoring study of urinary 3-PBA, which elucidated the background environmental exposure level of PYR in the Japanese general population without occupational exposure. Further nationwide studies covering different seasons and age distribution are needed to monitor the urinary 3-PBA levels in Japan.

Relationship between dietary habits and urinary concentrations of 3-phenoxybonzoic acid in a middle-aged and elderly general population in Japan

ObjectivesThe ingestion of pesticides in the daily diet is assumed to be the main modality of pesticide exposure for most people. A widely used class of pesticides in agricultural or residential settings is pyrethroid. We have examined the relationship between the intake frequency of selected items of vegetables and fruits and urinary metabolites of pyrethroid pesticides in a healthy general population.MethodsA total of 535 residents (184 men and 351 women) who attended a healthcare checkup program conducted in a rural area of Hokkaido, Japan, in August 2005 provided informed consent for their spot urine samples to be used for the determination of 3-phenoxybenzoic acid (3-PBA) levels. They also completed a self-administered questionnaire regarding the intake frequency of 12 food items. The concentrations of creatinine-corrected 3-PBA were predicted by the intake frequency of each item, using analysis-of-covariance models to adjust for age, sex, body mass index, and drinking and smoking status.ResultsBoth a significant association between the 3-PBA concentration and the frequency of tomato consumption and a significant positive linear trend was found in female subjects. In contrast, no such association was found in the male subjects.ConclusionsThe frequency of tomato consumption was confirmed to strongly predict the urinary pyrethroid metabolite levels in the general population—presumably because tomatoes are most often consumed raw and unpeeled (more so than all other vegetables and fruits analyzed in the current study). However, it should be noted that the 3-PBA levels, even among those subjects with the highest consumption of tomatoes, were far below the levels of toxicological significance, although the health consequences from long-term low-level exposure to pyrethroid requires further exploration.

Urinary concentrations of organophosphorus insecticide metabolites in Japanese workers

A recent development in analytical chemistry has enabled us to monitor systemic organophosphorus insecticide (OP) exposure at individual levels. At present, however, limited data are currently available on urinary OP metabolite levels worldwide. The purpose of this study was to assess urinary dialkylphosphate (DAP) concentrations in Japanese workers. Urine samples were collected in both summer and winter from 339 Japanese adults who worked as food distributors (FDs, n=164), apple farmers (AFs, n=147) and pest control operators (PCOs, n=28). DAPs were measured by gas chromatography-mass spectrometry after derivatization with pentafluorobenzylbromide. Dimethylphosphate (DMP), diethylphosphate (DEP), dimethylthiophosphate (DMTP) and diethylthiophosphate (DETP) were detected in the urine of over 87% of the studied populations in both seasons. The geometric mean values of total DAPs (nmol g(-1) creatinine), DMP, DMTP, DEP and DETP (μg g(-1) creatinine) in summer and winter were 106.7 and 98.3, 7.0 and 3.8, 3.4 and 4.5, 0.8 and 1.5, and 0.3 and 0.2 for the FDs, 440.8 and 197.7, 33.1 and 10.8, 10.1 and 5.8, 4.2 and 4.7 and 1.6 and 0.8 for the AFs, and 473.4 and 284.6, 28.9 and 22.2, 17.6 and 4.6, 3.5 and 4.4, and 0.5 and 0.6 for the PCOs, respectively, thereby revealing significantly higher concentrations in AFs and PCOs groups than in the FDs in both seasons except for winter DMTP. These DAP concentrations were approximately the same or at lower levels compared with those reported in the previous literature. This is one of the first studies to demonstrate urinary DAP concentrations in Japanese adults.

β-Glucuronidase activity is a sensitive biomarker to assess low-level organophosphorus insecticide exposure

Acetylcholinesterase and butyrylcholinesterase (BChE) activities in blood are widely used as the biomarkers for organophosphorus insecticide (OP) exposure. In the present study, we conducted a cross-sectional study to evaluate plasma beta-glucuronidase (BG), a sensitive biomarker candidate for OP exposure, BChE activities and urinary dialkyl phosphates (DAPs), OP metabolites. We assessed the relationship between these biomarker levels in the following groups: 32 controls (control), 21 pest control operators and their co-workers who had not sprayed OPs within 3 days prior to sample collection (PCO1), and 21 pest control operators who sprayed OPs within those 3 days (PCO2). Logarithmically transformed age-adjusted means of DAPs were 3.88, 5.62 and 6.45 nmol/g creatinine for control, PCO1 and PCO2, respectively (P<0.001 for difference, P<0.001 for trend). Logarithmically transformed age-adjusted means of BG were 1.40, 1.52 and 1.85 micromol/L/h for control, PCO1 and PCO2, respectively. BG activity, but not BChE, was increased according to their OP exposure level (P=0.038 for difference, P=0.026 for trend). It was concluded that plasma BG activity is more sensitive biomarker as well as urinary OP metabolites than BChE for low-level exposure in humans.

Involvement of multidrug resistance-associated protein 2 (ABCC2/Mrp2) in biliary excretion of micafungin in rats

The drug transporter, multidrug resistance-associated protein 2 (ABCC2/Mrp2), is known to play important roles in excretion of various drugs. In the present study, we investigated whether Mrp2 is involved in the transport of micafungin, a newly developed antifungal agent. When Sprague-Dawley rats received an intravenous injection of micafungin (1 mg/kg) in combination with cyclosporine, the cyclosporine significantly delayed the disappearance of micafungin from plasma and decreased the systemic clearance and volume of distribution at steady-state of micafungin to 54% and 65% of the corresponding control values, respectively. When Sprague-Dawley rats received a constant-rate infusion of micafungin, cyclosporine significantly decreased the steady-state biliary clearance of micafungin (approximately 80%). A significant decrease in the biliary clearance of micafungin (~60%) was observed in Eisai hyperbilirubinemic rats, which have a hereditary deficiency in Mrp2. The present findings at least suggest that Mrp2 is involved mainly in the hepatobiliary excretion of micafungin in rats.

Relationship between Urinary Pesticide Metabolites and Pest Control Operation among Occupational Pesticide Sprayers

Received Jun 23, 2007; Accepted Oct 16, 2008 Published online in J-ST AGE Dec 5, 2008 Correspondence to: T. Kondo, Program in Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, 1–1–20, Daikominami, Higashi-ku, Nagoya 461-8673, Japan (e-mail: taka@met.nagoya-u.ac.jp) Relationship between Urinary Pesticide Metabolites and Pest Control Operation among Occupational Pesticide Sprayers

Toxicokinetics of pyrethroid metabolites in male and female rats

The toxicokinetic characteristics of 3-phenoxybenzyl alcohol (3PBAlc) and 3-phenoxybenzaldehyde (3PBAld; metabolites of pyrethroid [PYR] after 25mg/kg, single intravenous administration), were investigated in male and female rats. The systemic clearance (Cl) of 3PBAlc in females (0.403±0.040l/h/kg) was significantly larger than that of males (0.227±0.036l/h/kg). The plasma concentration-time curve of 3PBAld decreased gradually and then increased again 1 and 2h after injection, suggesting the effect of enterohepatic circulation. The present study characterized the elimination and distribution of PYR metabolites and suggests that gender-related difference exists in the toxicokinetics of 3PBAlc and 3PBAld in rats.