Sustainable plant-wearable sensors for on-site, rapid decentralized detection of pesticides toward precision agriculture and food safety.

The synergy between eco-friendly biopolymeric films and printed devices leads to the production of plant-wearable sensors for decentralized analysis of pesticides in precision agriculture and food safety. Herein, a simple method for fabrication of flexible, and sustainable sensors printed on cellulose acetate (CA) substrates has been demonstrated to detect carbendazim and paraquat in agricultural, water and food samples. The biodegradable CA substrates were made by casting method while the full electrochemical system of three electrodes was deposited by screen-printing technique (SPE) to produce plant-wearable sensors. Analytical performance was assessed by differential pulse (DPV) and square wave voltammetry (SWV) in a linear concentration range between 0.1 and 1.0 µM with detection limits of 54.9 and 19.8 nM for carbendazim and paraquat, respectively. The flexible and sustainable non-enzymatic plant-wearable sensor can detect carbendazim and paraquat on lettuce and tomato skins, and also water samples with no interference from other pesticides. The plant-wearable sensors had reproducible response being robust and stable against multiple flexions. Due to high sensitivity and selectivity, easy operation and rapid agrochemical detection, the plant-wearable sensors can be used to detect biomarkers in human biofluids and be used in on-site analysis of other hazardous chemical substances.

Antioxidant potential of Pediococcus pentosaceus strains from the sow milk bacterial collection in weaned piglets.

BACKGROUND: In modern animal husbandry, breeders pay increasing attention to improving sow nutrition during pregnancy and lactation to favor the health of neonates. Sow milk is a main food source for piglets during their first three weeks of life, which is not only a rich repository of essential nutrients and a broad range of bioactive compounds, but also an indispensable source of commensal bacteria. Maternal milk microorganisms are important sources of commensal bacteria for the neonatal gut. Bacteria from maternal milk may confer a health benefit on the host. METHODS: Sow milk bacteria were isolated using culturomics followed by identification using 16S rRNA gene sequencing. To screen isolates for potential probiotic activity, the functional evaluation was conducted to assess their antagonistic activity against pathogens in vitro and evaluate their resistance against oxidative stress in damaged Drosophila induced by paraquat. In a piglet feeding trial, a total of 54 newborn suckling piglets were chosen from nine sows and randomly assigned to three treatments with different concentrations of a candidate strain. Multiple approaches were carried out to verify its antioxidant function including western blotting, enzyme activity analysis, metabolomics and 16S rRNA gene amplicon sequencing. RESULTS: The 1240 isolates were screened out from the sow milk microbiota and grouped into 271 bacterial taxa based on a nonredundant set of 16S rRNA gene sequencing. Among 80 Pediococcus isolates, a new Pediococcus pentosaceus strain (SMM914) showed the best performance in inhibition ability against swine pathogens and in a Drosophila model challenged by paraquat. Pretreatment of piglets with SMM914 induced the Nrf2-Keap1 antioxidant signaling pathway and greatly affected the pathways of amino acid metabolism and lipid metabolism in plasma. In the colon, the relative abundance of Lactobacillus was significantly increased in the high dose SMM914 group compared with the control group. CONCLUSION: P. pentosaceus SMM914 is a promising probiotic conferring antioxidant capacity by activating the Nrf2-Keap1 antioxidant signaling pathway in piglets. Our study provided useful resources for better understanding the relationships between the maternal microbiota and offspring. Video Abstract.

A highly selective and sensitive CdS fluorescent quantum dot for the simultaneous detection of multiple pesticides.

The abuse of pesticides has introduced a large number of residues in soil and drinking water, which can then enter the food chain and the human body. Monitoring pesticide residues and developing simple and fast detection systems for pesticide residues is urgently needed. In this study, we presented one-pot prepared CdS fluorescent quantum dots (QDs) and explored their sensing application for organic pesticides. The CdS QDs can sensitively and selectively detect three different pesticides, dichlorvos (DDVP), paraquat, and glufosinate-ammonium, through different fluorescence responses. Paraquat can effectively quench the fluorescence of the QDs and DDVP can cause remarkable fluorescent enhancement. Glufosinate-ammonium can induce both 150 nm fluorescent blueshifting and 30-fold fluorescent enhancement. The probe exhibited low detection limits for the three pesticides: 1.44 µM for paraquat, 0.23 mM for DDVP, and 49.8 µM for glufosinate-ammonium. Furthermore, based on the results, we utilized the powerful functions of smartphones to establish a concentration-gray value standard curve through RGB values and gray values to realize the qualitative detection and quantitative analysis of DDVP. It is believed that this work presents a new platform for the simultaneous detection of multiple pesticides using a single QDs probe. The present on-site method using a smartphone is of great potential for water monitoring in rural areas.

Glassy carbon electrode modified with carbon black and cross-linked alginate film: a new voltammetric electrode for paraquat determination.

A new electrode based on glassy carbon modified with an alginate film cross-linked with glutaraldehyde containing immobilized carbon black particles was successfully developed and applied for the determination of paraquat (PQ), a herbicide widely used for broadleaf weed control. Different polysaccharides (alginate, cellulose, pectin, starch, and chitosan) were investigated for the immobilization process, and alginate presented the highest chemical modifier potential for PQ determination. Additionally, the influence of chemical cross-linking agents (glutaraldehyde and epichlorohydrin) on the morphology, electrochemical response, and film stability was investigated. All experimental conditions were optimized, including the supporting electrolyte conditions (composition, pH, and concentration) and square wave voltammetry technical parameters. Under the optimized experimental conditions, the PQ analytical curve was linear from 0.4 to 2.0 mg L-1 and the limits of detection and quantification were 0.06 and 0.19 mg L-1, respectively. The proposed electrode is easy to obtain, stable, selective, sensitive, and low cost and was successfully applied for PQ determination in environmental and beverage samples. Graphical abstract.

Simultaneous determination of the quaternary ammonium pesticides paraquat, diquat, chlormequat, and mepiquat in barley and wheat using a modified quick polar pesticides method, diluted standard addition calibration and hydrophilic interaction liquid chromatography coupled to tandem mass spectrometry.

In this study, a modified Quick Polar Pesticides (QuPPe) method, optimized by a central composite design, was developed to determine quaternary ammonium pesticides (QUATs) residues in barley and wheat by ultra-high-performance liquid chromatographic tandem mass spectrometry (UHPLC-MS/MS) using a hydrophilic interaction chromatography (HILIC) column. Considering the high polarity of these compounds, special conditions of sample preparation and analysis are required. Different mobile phases, extraction procedure and clean-up were evaluated. An isocratic elution with aqueous solution of ammonium formate 60 mmol L-1 (pH 3.7) and acetonitrile, 40:60 (v/v), was selected. Water and acidified methanol as extraction solvent, without heating, and a clean-up with dichloromethane, chitosan and acetonitrile presented good results. The validated method presented satisfactory selectivity, linearity, matrix effect, trueness and precision, providing recoveries from 93 to 110% with RSD < 13% for barley, and 70 to 115% with RSD < 18% for wheat. The complexity of these matrices requires the calibration in matrix and the diluted standard addition calibration (DSAC) procedure has been shown to be an excellent option to compensate for the matrix effect and the losses of the analytes in the extraction. Real samples of barley and wheat were analyzed and 60% presented concentrations of paraquat above the maximum limits allowed by the European Union. The modified QuPPe method combined with DSAC and HILIC-UHPLC-MS/MS demonstrated to be an effective approach to determine QUATs in barley and wheat, and is a good alternative for routine analysis. The use of the biosorbent chitosan is effective, low cost and more ecological when compared to others conventional sorbents.

Determinação de paraquate em batatas / Determination of paraquat in potatoes

O Paraquate (1,1'-dimetil-4,4'-bipiridina- dicloreto) é herbicida amplamente utilizado em vários países para diferentes culturas. O objetivo é determinar a concentração de Paraquate em batatas comercializadas em diferentes estabelecimentos da zona leste de São Paulo. Foram coletadas 12 (doze) amostras de batatas adquiridas no comércio varejista (sacolões, ou seja, do de frutas, verduras e legumes; supermercados e feiras livres) da zona leste do município de São Paulo. A quantificação do Paraquate foi baseada na reação de complexação com o ditionito de sódio, gerando composto de cor azulada, cuja absorvância foi lida em espectrofotômetro em comprimento de onda de 600nm. Foi construída a curva padrão e a determinada a equação da reta (y = 1,6448x e R2= 0,9945). O limite de tolerância do herbicida em alimentos é de 0,2 partes por milhão ou 0,2 mg/kg, enquanto que a ingestão diária aceitável (IDA) é de 0,004 mg/kg de peso corpóreo. Assim, pode-se observar que os valores encontrados em três amostras estão acima do limite máximo permitido, enquanto quatro apresentaram concentrações muito próximas ao limite. Os resultados permitem inferir que existe a necessidade de intensificação na fiscalização nos locais de comercialização de alimentos produzidos com a utilização de agrotóxicos.(AU)

Paraquat (1,1'-dimethyl-4,4'- bipyridine-dichloride) is herbicide widely used in several countries in different plantations. The objective is to determine the concentration of Paraquat in potatoes, marketed in different establishments in the eastern zone of São Paulo. Twelve (12) samples of potatoes purchased from the retail trade ("sacolões", ie fruit, vegetable and vegetable markets, supermarkets and free markets) were collected from the eastern part of the city of São Paulo. The quantification of Paraquat was based on the reaction of complexation with the sodium dithionite, generating compound of blue color, whose absorbance was read in a spectrophotometer at wavelength of 600 nm. The standard curve was constructed and the equation of the line was determined (y = 1,6448x e R2 = 0,9945). The tolerance limit of the herbicide in foods is 0.2 parts per million or 0.2 mg/kg, while the acceptable daily intake (ADI) is 0.004 mg/kg body weight. Thus, it can be observed that the values found in three samples are above the maximum allowed limit, while four of them presented concentrations very close to the limit. The results allow inferring that there is a need for intensification in the inspection in the commercial places of food produced with the use of pesticides.

Ion-pair switchable-hydrophilicity solvent-based homogeneous liquid-liquid microextraction for the determination of paraquat in environmental and biological samples before high-performance liquid chromatography.

An approach involving ion-pair switchable-hydrophilicity solvent-based homogeneous liquid-liquid microextraction coupled to high-performance liquid chromatography has been applied for the preconcentration and separation of paraquat in a real sample. A mixture of triethylamine and water was used as the switchable-hydrophilicity solvent. The pH was regulated using carbon dioxide; hence the ratio of the ionized and non-ionized form of triethylamine could control the optimum conditions. Sodium dodecyl sulfate was utilized as an ion-pairing agent. The ion-associate complex formed between the cationic paraquat and sodium dodecyl sulfate was extracted into triethylamine. The separation of the two phases was carried out by the addition of sodium hydroxide, which changed the ionization state of triethylamine. The effects of some important parameters on the extraction recovery were investigated. Under the optimum conditions (500 µL of the extraction solvent, 1 mg sodium dodecyl sulfate, 2.0 mL of 10 mol/L sodium hydroxide, and pH 4), the limit of detection and the limit of quantification were 0.2 and 0.5 µg/L, respectively, with preconcentration factor of 74. The precision (RSD, n = 10) was  <5%. The recovery of the analyte in environmental and biological samples was in the range of 90.0-92.3%.

Facile Synthesis of Glutathione-capped CdS Quantum Dots as a Fluorescence Sensor for Rapid Detection and Quantification of Paraquat.

This paper describes a convenient and rapid fluorescence sensor for determination of paraquat (PA) based on glutathione-capped CdS quantum dots (QDs). The methodology enabled the use of a simple synthesis procedure for water solubilization of CdS QDs via a fast route using glutathione as a capping agent within 15 min. The resulting water-soluble QDs exhibit a strong fluorescence emission at 536 nm with high and reproducible photostability. PA is an important class of electron acceptors for QDs. Thus, the fluorescence intensity of the glutathione-capped CdS QDs probe could be dramatically quenched by PA due to the electron transfer mechanism. The fluorescence intensity of the CdS QDs system was proportional to PA concentration in the range of 0.025 to 1.5 µg mL(-1), with a detection limit of 0.01 µg mL(-1). The time of analysis sample, including preparation of QDs and fluorescent measurement for PA, was only 20 min. Most of the potentially coexisting substances did not interfere with the PA-induced quenching effect except diquat. Furthermore, the analytical applicability of the proposed method was demonstrated by analyzing PA in water, rice and cabbage samples, and the recoveries were between 86 and 105% which satisfied the requirement of detection for PA. These results showed that the proposed method was simple in design and fast in operation, and could be used as a sensitive tool for detecting PA in environmental and agricultural samples.

Phytoextraction potential of wild type and 35S-gshI transgenic poplar trees (Populus x Canescens) for environmental pollutants herbicide paraquat, salt sodium, zinc sulfate and nitric oxide in vitro.

Phytoextraction potentials of two transgenic (TR) poplar (Populus x canescens) clones TRggs11 and TRlgl6 were compared with that of wild-type (WT) following exposure to paraquat, zinc sulfate, common salt and nitric oxide (NO), using a leaf-disc system incubated for 21 days on EDTA-containing nutritive WPM media in vitro. Glutathione (GSH) contents of leaf discs of TRlgl6 and TRggs11 showed increments to 296% and 190%, respectively, compared with WT. NO exposure led to a twofold GSH content in TRlgl6, which was coupled with a significantly increased sulfate uptake when exposed to 10(-3) M ZnSO4. The highest mineral contents of Na, Zn, Mn, Cu, and Mo was observed in the TRggs11 clone. Salt-induced activity of catalase enzyme increased in both TR clones significantly compared with WT under NaCl (0.75% and 1.5%) exposure. The in silico sequence analyses of gsh1 genes revealed that P. x canadensis and Salix sachalinensis show the closest sequence similarity to that of P. x canescens, which predicted an active GSH production with high phytoextraction potentials of these species with indication for their use where P. x canescens can not be grown.

Validity of geographically modeled environmental exposure estimates.

Geographic modeling is increasingly being used to estimate long-term environmental exposures in epidemiologic studies of chronic disease outcomes. However, without validation against measured environmental concentrations, personal exposure levels, or biologic doses, these models cannot be assumed a priori to be accurate. This article discusses three examples of epidemiologic associations involving exposures estimated using geographic modeling, and identifies important issues that affect geographically modeled exposure assessment in these areas. In air pollution epidemiology, geographic models of fine particulate matter levels have frequently been validated against measured environmental levels, but comparisons between ambient and personal exposure levels have shown only moderate correlations. Estimating exposure to magnetic fields by using geographically modeled distances is problematic because the error is larger at short distances, where field levels can vary substantially. Geographic models of environmental exposure to pesticides, including paraquat, have seldom been validated against environmental or personal levels, and validation studies have yielded inconsistent and typically modest results. In general, the exposure misclassification resulting from geographic models of environmental exposures can be differential and can result in bias away from the null even if non-differential. Therefore, geographic exposure models must be rigorously constructed and validated if they are to be relied upon to produce credible scientific results to inform epidemiologic research. To our knowledge, such models have not yet successfully predicted an association between an environmental exposure and a chronic disease outcome that has eventually been established as causal, and may not be capable of doing so in the absence of thorough validation.

Quantification of Paraquat, MPTP, and MPP+ in brain tissue using microwave-assisted solvent extraction (MASE) and high-performance liquid chromatography-mass spectrometry.

Animal models, consistent with the hypothesis of direct interaction of paraquat (PQ) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) with specific areas of the central nervous system have been developed to study Parkinson's disease (PD) in mice. These models have necessitated the creation of an analytical method for unambiguous identification and quantitation of PQ and structurally similar MPTP and 1-methyl-4-phenylpyridinium ion (MPP+) in brain tissue. A method for determination of these compounds was developed using microwave-assisted solvent extraction (MASE) and liquid chromatography-mass spectrometry. Extraction solvent and microwave conditions such as power and time were optimized to produce recoveries of 90% for PQ 78% for MPTP and 97% for its metabolite MPP+. The chromatographic separation was performed on a C8, column and detection was carried out using an ion trap as an analyzer with electrospray ionization. Mass spectrometer parameters such as heated capillary temperature, spray voltage, capillary voltage and others were also optimized for each analyte. Analysis was done in selective ion-monitoring (SIM) mode using m/z 186 for PQ, m/z 174 for MPTP, and m/z 170 for MPP+. The method detection limit for paraquat in matrix was 100 pg, 40 pg for MPTP, and 20 pg MPP+.

Parkinson's disease and residential exposure to maneb and paraquat from agricultural applications in the central valley of California.

Evidence from animal and cell models suggests that pesticides cause a neurodegenerative process leading to Parkinson's disease (PD). Human data are insufficient to support this claim for any specific pesticide, largely because of challenges in exposure assessment. The authors developed and validated an exposure assessment tool based on geographic information systems that integrated information from California Pesticide Use Reports and land-use maps to estimate historical exposure to agricultural pesticides in the residential environment. In 1998-2007, the authors enrolled 368 incident PD cases and 341 population controls from the Central Valley of California in a case-control study. They generated estimates for maneb and paraquat exposures incurred between 1974 and 1999. Exposure to both pesticides within 500 m of the home increased PD risk by 75% (95% confidence interval (CI): 1.13, 2.73). Persons aged < or =60 years at the time of diagnosis were at much higher risk when exposed to either maneb or paraquat alone (odds ratio = 2.27, 95% CI: 0.91, 5.70) or to both pesticides in combination (odds ratio = 4.17, 95% CI: 1.15, 15.16) in 1974-1989. This study provides evidence that exposure to a combination of maneb and paraquat increases PD risk, particularly in younger subjects and/or when exposure occurs at younger ages.

Supercritical fluid extraction as an on-line clean-up technique for rapid amperometric screening and alternative liquid chromatography for confirmation of paraquat and diquat in olive oil samples.

A rapid and simple method for the direct screening of paraquat (PQ) and diquat (DQ) in olive oil samples is proposed. The sample screening method involves supercritical fluid extraction (SFE) (clean-up followed by the extraction of the analytes) followed by continuous flow electrochemical detection. Those samples for which the total concentration is close to or above the threshold limit established by the Columbian Society for Social Protection (0.05 microg g(-1)) are subsequently analyzed by liquid chromatography (LC) with diode array detection (DAD). This confirmation method allows the determination of PQ and DQ in the range between 0.04 and 1.0 microg g(-1), with average relative standard deviations lower than 3.5%, and 0.003 and 0.002 microg g(-1) detection limits for PQ and DQ, respectively. The proposed arrangement opens up interesting prospects for the direct determination of polar pesticides in complex samples with a good throughput and a high level of automation.

Quantitative determination of paraquat in meconium by sodium borohydride-nickel chloride chemical reduction and gas chromatography/mass spectrometry (GC/MS).

The objective of this study was to develop a procedure for the GC/MS assay of paraquat in meconium as a biomarker of fetal exposure to paraquat. The method involved a sodium borohydride-nickel chloride reduction procedure, liquid-liquid extraction of the perhydrogenated product, concentration, and GC/MS assay. The method demonstrated good overall recovery (102.56%) with %CV (inter-assay) of less than 13%, and a limit of detection of 0.0156microg/g. Analysis of meconium samples from a study population in the Philippines (n=70) showed a 2.8% prevalence of fetal exposure to paraquat.

Efeito tóxico dos praguicidas maneb e paraquat sobre a atividade da enzima antioxidante catalase em ratos / Toxic effect of pesticides maneb and paraquat on catalase antioxidant enzyme activity in rats

Os radicais livres estão envolvidos em um grande número de enfermidades do ser humano.O cérebro tem níveis baixos de enzimas antioxidantes e um conteúdo lípidico elevado, tornando-se muito susceptível ao ataque de espécies reativas de oxigênio.Neste trabalho avaliou-se a lipoperoxidação em hipocampo e a atividade da enzima catalase em estriado e hipocampo de ratos tratados com o fungicida maneb (30 mg/kg) e o herbicida paraquat (10 mg/kg).Não houve alteração na lipoperoxidação nem na atividade enzimática no hipocampo dos animais tratados com ambos os praguicidas, porém foi observada uma inibição da catalase no estriado dos ratos tratados com maneb e com paraquat.Com estes resultados pode-se sugerir, de forma preliminar, uma ação tóxica maior sobre centros dopaminérgicos.Estudos sobre a toxicidade destes compostos são essenciais na compreensão do papel destes praguicidas e dos radicais livres na etiologia das doenças

Simultaneous determination of pesticides using a four-band disposable optical capillary immunosensor.

The development of a four-band capillary optical immunosensor for the simultaneous determination of mesotrione, hexaconazole, paraquat, and diquat is described. Four distinct bands (each corresponding to a different analyte) are created in the internal walls of a plastic capillary by immobilizing protein conjugates of the analytes. To perform the assay, the capillary is filled with a mixture of anti-analyte-specific antibodies together with a standard or sample containing the analyte(s). After a short incubation, a mixture of the appropriate second antibodies labeled with fluorescein is introduced into the capillary. To measure the fluorescence intensity bound onto each band, the capillary was scanned, perpendicularly to its axis, by a laser light beam. Part of the emitted photons were trapped into the capillary walls and waveguided to a photomultiplier placed at the one end of the capillary. The analytical characteristics of the assays of mesotrione, paraquat, diquat, and hexaconazole were as follows: detection limits of 0.04, 0.06, 0.09, and 0.10 ng/mL, respectively; dynamic ranges up to 9, 6, 12, and 15 ng/ mL, respectively, intra- and interassay CVs less than 10%. The analytical characteristics of the assays were comparable with those of the corresponding single-analyte fluoroimmunoassays performed in microtitration wells, proving the ability of the proposed immunosensor for reliable multianalyte determinations. Moreover, the combination of low-cost disposable plastic capillary tubes with the low consumption of reagents, the short assay time, and the multianalyte feature of the proposed immunosensor indicates its potential for environmental analysis.

Determination of quaternary ammonium pesticides by liquid chromatography-electrospray tandem mass spectrometry.

A method for the direct determination of paraquat, diquat, chlormequat and difenzoquat in water samples, using an on-line solid-phase extraction-liquid chromatography-tandem mass spectrometry system was developed. No sample preparation was required and the detection limits were below the European Union maximum residue levels. The chromatographic separation was performed using an XTera MS C8 column. The concentration of the ion pair reagent, the pH and the gradient elution were optimized to give high recoveries and good chromatographic resolution between quats. The detection was carried out using an ion trap as mass analyzer. Parameters such as the magnitude and duration of the resonant excitation voltage and the magnitude of the trapping RF voltage for full scan tandem mass spectrometry (MS-MS) experiments were studied to establish the optimal experimental conditions. Moreover, the accurate optimization of these parameters allowed MS-MS experiments of low mass ions, below m/z 200, providing unambiguous peak identification. Finally, the reproducibility of the proposed method was shown by good run-to-run and day-to-day precision values and its applicability to the determination of quats in drinking water was evaluated using spiked samples.

Selective kinetic determination of paraquat using long-wavelength fluorescence detection.

The reaction between paraquat, ascorbic acid, and Cresyl Violet in alkaline medium and in the presence of sodium dodecyl sulfate has been applied for the first time to the development of a kinetic-fluorometric method for the determination of paraquat. The reaction rate of this system is measured by using the stopped-flow mixing technique, which makes the method applicable to automatic routine analysis. Analytical data are obtained in approximately 30 s. The calibration graph is linear over the range 6-500 ng mL(-)(1), and the detection limit is 1.8 ng mL(-)(1). The relative standard deviation is <3%. The use of dynamic measurements at long wavelength favors the high selectivity of the method. Diquat behaves in this system similarly to paraquat, but its interferent effect is easily avoided by using cysteine. The proposed method has been applied to the determination of paraquat in tap water, milk, and white wine samples with recoveries of 89-104%.

Biochemical studies on the toxicity of 1, 1'-dimethyl-4, 4'-bipyridylium dichloride in the rat.

The effect of intraperitoneal administration of lethal dose (50 mg/kg) of paraquat on the microsomal cysteine levels in the plasma, liver and lung of adult male Wistar rats has been investigated using Rank Chromaspek amino acid analyzer. The microsomal alanine levels were also determined to help in assessing the extent of paraquat interference with cellular protein. DL-Buthionine-[S,R]-Sulfoximine (BSO) and Diethyl maleate (DEM) were used to potentiate the toxic effect of the bipyridyl. The microsomal cysteine levels were significantly (P < or = 0.05) depressed in the plasma, liver and lung of the paraquat-treated rats compared with the saline-injected group but the alanine levels were not similarly affected. Probably, paraquat poisoning interferes specifically with the cellular cysteine content in the rat. These findings could provide a valuable information on the biochemical mechanism of paraquat intoxication.

Detection of drugs and poisons in postmortem tissues--determination of paraquat in tissues of rabbits buried underground.

The possibility of detecting paraquat in tissues of rabbits buried underground over a 2-year period was examined. Paraquat (1.2 g) was given orally to rabbits, which were sacrificed 1 h after administration. The animals were buried underground, and the skeletal muscles and the bones were collected 3 and 6 months after death, and 3, 6, 12, and 24 months after death, respectively. Paraquat was present in all bone marrow samples, showing a slight decrease in concentration until 12 months. Paraquat was also detected in all skeletal muscle samples, showing almost no change in concentration until 6 months. These results indicate that intoxication with paraquat as well as the degree of poisoning can both be determined from the skeletal muscles and bone marrow of cadavers which have been buried underground for a long period of time even in human cases.