Established Tolerance Levels Research Articles

Clinical implementation of 3D in vivo dosimetry for abdominal and pelvic stereotactic treatments

PurposeTo analyze results from three years of in vivo transit EPID dosimetry of abdominal and pelvic stereotactic radiotherapy and to establish tolerance levels for routine clinical use. Material80 stereotactic VMAT treatments (152 fractions) targeting the abdomen or pelvis were analyzed. In vivo 3D doses were reconstructed with an EPID commercial algorithm. Gamma Agreement Index (GAI) and DVH differences in Planning Target Volume (PTV) and Clinical Target Volume (CTV) were evaluated. Initial tolerance level was set to GAI > 85% in PTV. Fractions Over Tolerance Level (OTL) were deemed to be due to set-up errors, incorrect use of immobilization devices, 4D errors, transit EPID algorithm errors and unknown/unidentified errors. Statistical Process Control (SPC) was applied to determine local tolerance levels. ResultsAverage GAI were (82.7 ± 20.9) % in PTV and (72.9 ± 29.7) % in CTV. 37.8% of fractions resulted OTL and were classified as: set-up errors (3.3%), incorrect use of immobilization devices (2.1%), 4D errors (2.1%), EPID transit algorithm errors (17.1%). OTL causes for the remaining 13.2% of fractions were not identified. The differences between PTV and CTV measured in vivo and calculated mean dose (average difference ± standard deviation) were (−3.3% ± 3.2%) and (−2.3% ± 3.0%). When tolerance levels based on SPC to PTV mean dose differences were applied, the percentage of OTL decreased to 7% and no EPID algorithm error occurred. One error was not identified. ConclusionsThe application of local tolerance levels to EPID in vivo dosimetry proved to be useful for detecting extra-lung SBRT treatment errors.

Forecast Informed Reservoir Operations Using Ensemble Streamflow Predictions for a Multipurpose Reservoir in Northern California

AbstractEnsemble Forecast Operations (EFO) is a risk‐based approach of reservoir flood control operations that incorporates ensemble streamflow predictions (ESPs) made by the California‐Nevada River Forecast Center. Reservoir operations for each member of an ESP are individually modeled to forecast system conditions and calculate risk of reaching critical operational thresholds. Reservoir release decisions are simulated to manage forecasted risk with respect to established risk tolerance levels. EFO was developed for Lake Mendocino, a 111,000 acre‐foot reservoir near Ukiah, California, to evaluate its viability to improve reservoir storage reliability without increasing downstream flood risk. Lake Mendocino is a dual use reservoir, owned and operated for flood control by the United States Army Corps of Engineers and operated for water supply by Sonoma Water. EFO was simulated using a 26‐year (1985–2010) ESP hindcast generated by the California‐Nevada River Forecast Center, which provides 61‐member ensembles of 15‐day flow forecasts. EFO simulations yield generally higher storage levels during the flood management season while maintaining needed flood storage capacity by strategically prereleasing water in advance of forecasted storms. Model results demonstrate a 33% increase in median storage at the end of the flood management season (10 May) over existing operations without marked changes in flood frequency for locations downstream from Lake Mendocino. EFO may be a viable alternative for managing flood control operations at Lake Mendocino that provides multiple benefits (water supply, flood mitigation, and ecosystems) and provides a management framework that could be adapted and applied to other flood control reservoirs.

OA036] Clinical implementation and evaluation of the Mobius3D system for independent dose calculation

Purpose The complexity of dose planning and treatment delivery systems has increased and necessitates a more comprehensive physics quality assurance (QA). These QA checks can, however, be quite time consuming. Therefore, there is a need for automation of QA which usually rely on empirically established tolerance levels. Mobius3D is a commercial fully automated QA system that uses a collapsed cone convolution/superposition algorithm for verification of treatment plans. The purpose of this study was to investigate the level of deviation between this system and the clinical commissioned treatment planning system (Eclipse v.13.5) using the Anisotropic Analytical Algorithm when the MLC modeling was optimized. Methods The Mobius3D system comes with golden beam data and calculates the dose on the patient CT data set. For MLC optimization, 8 IMRT/VMAT plans from various anatomical regions were included and recalculated in a cylindrical plastic phantom containing two planar diode arrays (Delta4 phantom, ScandiDos). The plans were then verified experimentally at the accelerator and all passed a local 3%/2 mm gamma criteria (passing rate > 90%). The dosimetric leaf gap (DLG) used to model the MLC in Mobius3D was optimized to keep the PTV mean dose of the 8 plans within 2% in the Delta4 geometry resulting in a +0.6 mm adjustment of the DLG from the default value. To establish the level of dose deviation and establish acceptance criteria, 34 treatment plans in different geometries, such us lung (10), head and neck (HN, 10), and pelvis (14) were evaluated for both IMRT and VMAT. Results The absolute mean and max PTV dose deviation for (lung/HN/pelvis) were: 0.8/2.2/2.1% and 1.4/2.9/2.8%. All max deviations were positive, i.e. a higher dose estimate by Mobius3D. 5 HN IMRT plans before DLG adjustment all showed negative deviations of −3.12/−3.8% (PTV mean/max). Conclusions A random sample of treatment plans were within 2.5% in absolute mean dose of the PTV between Mobius3D and the TPS. MLC parameter optimization plays an important role in establishing an acceptance criterion.

Multi-institutional MicroCT image comparison of image-guided small animal irradiators

To recommend imaging protocols and establish tolerance levels for microCT image quality assurance (QA) performed on conformal image-guided small animal irradiators. A fully automated QA software SAPA (small animal phantom analyzer) for image analysis of the commercial Shelley micro-CT MCTP 610 phantom was developed, in which quantitative analyses of CT number linearity, signal-to-noise ratio (SNR), uniformity and noise, geometric accuracy, spatial resolution by means of modulation transfer function (MTF), and CT contrast were performed. Phantom microCT scans from eleven institutions acquired with four image-guided small animal irradiator units (including the commercial PXi X-RAD SmART and Xstrahl SARRP systems) with varying parameters used for routine small animal imaging were analyzed. Multi-institutional data sets were compared using SAPA, based on which tolerance levels for each QA test were established and imaging protocols for QA were recommended. By analyzing microCT data from 11 institutions, we established image QA tolerance levels for all image quality tests. CT number linearity set to R2 > 0.990 was acceptable in microCT data acquired at all but three institutions. Acceptable SNR > 36 and noise levels <55 HU were obtained at five of the eleven institutions, where failing scans were acquired with current-exposure time of less than 120 mAs. Acceptable spatial resolution (>1.5 lp mm−1 for MTF = 0.2) was obtained at all but four institutions due to their large image voxel size used (>0.275 mm). Ten of the eleven institutions passed the set QA tolerance for geometric accuracy (<1.5%) and nine of the eleven institutions passed the QA tolerance for contrast (>2000 HU for 30 mgI ml−1). We recommend performing imaging QA with 70 kVp, 1.5 mA, 120 s imaging time, 0.20 mm voxel size, and a frame rate of 5 fps for the PXi X-RAD SmART. For the Xstrahl SARRP, we recommend using 60 kVp, 1.0 mA, 240 s imaging time, 0.20 mm voxel size, and 6 fps. These imaging protocols should result in high quality images that pass the set tolerance levels on all systems. Average SAPA computation time for complete QA analysis for a 0.20 mm voxel, 400 slice Shelley phantom microCT data set was less than 20 s. We present image quality assurance recommendations for image-guided small animal radiotherapy systems that can aid researchers in maintaining high image quality, allowing for spatially precise conformal dose delivery to small animals.

Method validation for 243 pesticides and environmental contaminants in meats and poultry by tandem mass spectrometry coupled to low-pressure gas chromatography and ultrahigh-performance liquid chromatography

An easy and reliable high-throughput analysis method was developed and validated for 192 diverse pesticides and 51 environmental contaminants (13 PCB congeners, 14 PAHs, 7 PBDE congeners, and 17 novel flame retardants) in cattle, swine, and poultry muscle. Sample preparation was based on the “quick, easy, cheap, effective, rugged and safe” (QuEChERS) approach using filter-vial dispersive solid-phase extraction (d-SPE) cleanup. Split final extracts were analyzed in parallel by low-pressure (vacuum outlet) GC-MS/MS and UHPLC-MS/MS (10 min each), providing an additional degree of confirmation for 55 overlapping LC- and GC-amenable pesticides. Analyte protectants were utilized to improve sensitivity and decrease matrix effects in GC analysis, and only filtration of initial extracts was enough to avoid ion suppression in UHPLC-MS/MS. The method was validated at three spiking levels (10, 25, and 100 ng/g) at or below established tolerance levels in the sample types. Satisfactory recoveries (70–120%) and RSDs ≤ 20% were achieved for 200 analytes. The validated method was successfully applied to the analysis of real-world incurred meat samples, further demonstrating the utility of the method for implementation in regulatory and commercial laboratories.

ESTIMATION OF THE WITHDRAWAL PERIOD FOR AMOXICILLIN IN POMPANO (TRACHINOTUS BLOCHII) SERUM AND MUSCLE

Amoxicillin is one of the most popular antibiotics used in aquaculture. To ensure the residue of amoxicillin in the serum and the muscle of pompano (Trachinotus blochii) is below the established tolerance levels; we used reversed phase high-performance liquid chromatography (HPLC) to measure the amoxicillin in pompano after oral administration. The pharmacokinetics of amoxicillin in the serum and the muscle of pompano were established by single oral administration or administrations for five consecutive days at the dose of 40 mg/kg. After different depletion periods, amoxicillin residue was analyzed in both the serum and the muscle fillets by HPLC. The verified concentrations of this method were 0.01 to 10 μg/mL; the limit of detection (LOD) and the limit of quantitation (LOQ) were 0.04 and 0.1 μg/g. The concentration of amoxicillin in the serum of pompano reached the maximum threshold of 7.36 μg/g after 0.5 h depletion in the experiment with a single dose of amoxicillin (40 mg/kg of body weight). In addition, the maximal concentration (1.96 μg/g) of amoxicillin was detected in the muscle 2 h after depletion. Furthermore, the residue levels had decreased below the limit of detection after 48 h and 72 h in the serum and the muscle. Here we also suggested that 5 days of withdrawal were required after the multiple dosing of amoxicillin.

SU-E-T-390: Monitorization of the Dynamic Multi-Leaf Collimator Performance Using Log Files - a Quality Assurance Tool for Intensity Modulated Radiotherapy.

Commission baseline values of the multi-leaf collimator (MLC) using Varian's dynalog file viewer software (DFV) and establish tolerance levels to use as a periodic quality assurance tool in intensity modulated radiotherapy (IMRT). A sliding window test was created to have all leafs moving at a constant high speed of 2.5cm/s. This test was performed for 100 days at gantry angles of 0°, 90° and 270° during the morning quality checks in an accelerator performing RapidArc treatments with a Millennium 120 MLC. The DFV was used to collect the percentage of counts in bins 1 (0.05mm) to 8 (deviations in steps of 0.5mm) and the root mean square error (RMS). These were analyzed statistically and a baseline value and tolerance levels were established. Results show that the greater percentage of counts is found at bin 4 with an average of 97%. Bins 1 to 3 have less than 1 % and bin 5 presents an average of 1.7%. As for bin 6, the average was below 0.1%. Bins 7 and 8 presented no counts. When comparing the results of the different gantry angles, significant differences are only found in bin 4 and 5, with a better performance for the 0° gantry. As for the RMS error, no difference was found between different carriages or gantry angles and the average value was 0.129. A tolerance level was established for bins that correspond to greater deviations - bins 5 to 8, with an upper limit equivalent to twice the standard deviation of each bin. With the introduction of IMRT, the MLC quality assurance became more extensive and thorough. However a quantitative analysis is often difficult to interpret and time consuming. The purposed method allows the monitorization of the stability and performance of the MLC in a quantitative and easy way.

Optimization and Validation of a Multiclass Screening and Confirmation Method for Drug Residues in Milk Using High-Performance Liquid Chromatography/Tandem Mass Spectrometry

The further optimization and validation of a multiresidue veterinary drug screening method for milk is described. The drug residues of regulatory interest in milk include beta-lactams, sulfonamides, tetracyclines, fluoroquinolones, and macrolides. A previously published procedure has been modified to incorporate new compounds and to collect both screening and confirmatory ion transitions in one acquisition method. Milk samples were extracted with an equal volume of acetonitrile. The samples were then subjected to cleanup with a bonded SPE cartridge and a MW cutoff filter. The SPE protocol was modified to effectively recover a metabolite of flunixin. Established tolerance levels are set for most of these drugs in milk; thus, the screening procedure was semiquantitative, using positive controls for comparison. The positive controls, consisting of extracts from milk fortified with the drugs at their tolerance or safe level, were used to set statistically valid minimum response criteria for unknown samples. This updated method was validated with fortified milk, as well as with milk samples from animals administered veterinary drugs.

Comparison of the efficiency of different extraction methods for the simultaneous determination of mycotoxins and pesticides in milk samples by ultra high-performance liquid chromatography-tandem mass spectrometry

A rapid multi-analyte method has been developed for the simultaneous determination of pesticides and mycotoxins in milk by ultra high-performance liquid chromatography coupled to triple quadrupole mass spectrometry (UHPLC-QqQ-MS/MS). A variety of methodologies has been evaluated, including solid-phase extraction (SPE), "dilute-and-shoot" (liquid-liquid extraction-based procedures), and QuEChERS (quick, easy, cheap, effective, rugged, and safe)-based methods. The optimization and development process was carried out considering that the maximum residue level for aflatoxin M1 (AFM1) in milk in the European Union (EU) is set at 0.05 μg kg(-1), which is the lowest tolerance in the target compounds. The selected method consisted of an extraction by SPE using C18 as sorbent and methanol as elution solvent. The final determination was performed by UHPLC-QqQ-MS/MS. Matrix-matched standard calibration was used for quantification, obtaining recoveries in the range 60-120% with relative standard deviations <25%, at three spiking levels: 0.5, 10, and 50 μg kg(-1) (ten times lower for AFM1). Limits of quantification ranged from 0.20 to 0.67 μg kg(-1), which were always below or equal to the established tolerance levels by the EU. Finally, the selected method was applied to different types of milk.

Multi‐class, multi‐residue liquid chromatography/tandem mass spectrometry screening and confirmation methods for drug residues in milk

This paper describes the development and optimization of a multi-residue veterinary drug screening method for whole milk. The drug residues of regulatory interest in milk include beta-lactams, sulfonamides, tetracyclines, fluoroquinolones, and macrolides. Milk samples were extracted with acetonitrile and the samples were then subjected to a clean-up procedure using a bonded solid-phase extraction cartridge and a molecular weight cut-off filter. Liquid chromatography/tandem mass spectrometry (LC/MS/MS) triple quadrupole electrospray methods were developed to monitor for the drugs in milk. Since established tolerance levels are set for most of these drugs in milk, the initial screening procedure was semi-quantitative, where samples were compared to the response of a positive control. The positive control, consisting of an extract from a portion of milk fortified with the drugs at half their allowed levels, was used to set the laboratory's minimum response criteria for unknown samples. Confirmatory analyses, with additional ion transitions for each residue, were performed on the same extracts.

Toxins of cyanobacteria

Blue-green algae are found in lakes, ponds, rivers and brackish waters throughout the world. In case of excessive growth such as bloom formation, these bacteria can produce inherent toxins in quantities causing toxicity in mammals, including humans. These cyanotoxins include cyclic peptides and alkaloids. Among the cyclic peptides are the microcystins and the nodularins. The alkaloids include anatoxin-a, anatoxin-a(S), cylindrospermopsin, saxitoxins (STXs), aplysiatoxins and lyngbyatoxin. Both biological and chemical methods are used to determine cyanotoxins. Bioassays and biochemical assays are nonspecific, so they can only be used as screening methods. HPLC has some good prospects. For the subsequent detection of these toxins different detectors may be used, ranging from simple UV-spectrometry via fluorescence detection to various types of MS. The main problem in the determination of cyanobacterial toxins is the lack of reference materials of all relevant toxins. In general, toxicity data on cyanotoxins are rather scarce. A majority of toxicity data are known to be of microcystin-LR. For nodularins, data from a few animal studies are available. For the alkaloids, limited toxicity data exist for anatoxin-a, cylindrospermopsin and STX. Risk assessment for acute exposure could be relevant for some types of exposure. Nevertheless, no acute reference doses have formally been derived thus far. For STX(s), many countries have established tolerance levels in bivalves, but these limits were set in view of STX(s) as biotoxins, accumulating in marine shellfish. Official regulations for other cyanotoxins have not been established, although some (provisional) guideline values have been derived for microcystins in drinking water by WHO and several countries.

Confirmatory and Quantitative Analysis of β-Lactam Antibiotics in Bovine Kidney Tissue by Dispersive Solid-Phase Extraction and Liquid Chromatography−Tandem Mass Spectrometry

A simple, rapid, rugged, sensitive, and specific method for the confirmation and quantitation of 10 beta-lactam antibiotics in fortified and incurred bovine kidney tissue has been developed. The method uses a simple solvent extraction, dispersive solid-phase extraction (dispersive-SPE) cleanup, and liquid chromatography-tandem mass spectrometry (LC/MS/MS) for confirmation and quantitation. Dispersive-SPE greatly simplifies and accelerates sample cleanup and improves overall recoveries compared with conventional SPE cleanup. The beta-lactam antibiotics tested were as follows: deacetylcephapirin (an antimicrobial metabolite of cephapirin), amoxicillin, desfuroylceftiofur cysteine disulfide (DCCD, an antimicrobial metabolite of ceftiofur), ampicillin, cefazolin, penicillin G, oxacillin, cloxacillin, naficillin, and dicloxacillin. Average recoveries of fortified samples were 70% or better for all beta-lactams except DCCD, which had an average recovery of 58%. The LC/MS/MS method was able to demonstrate quantitative recoveries at established tolerance levels and provide confirmatory data for unambiguous analyte identification. The method was also tested on 30 incurred bovine kidney samples obtained from the USDA Food Safety and Inspection Service, which had previously tested the samples using the approved semiquantitative microbial assay. The results from the quantitative LC/MS/MS analysis were in general agreement with the microbial assay for 23 samples although the LC/MS/MS method was superior in that it could specifically identify which beta-lactam was present and quantitate its concentration, whereas the microbial assay could only identify the type of beta-lactam present and report a concentration with respect to the microbial inhibition of a penicillin G standard. In addition, for 6 of the 23 samples, LC/MS/MS analysis detected a penicillin and a cephalosporin beta-lactam, whereas the microbial assay detected only a penicillin beta-lactam. For samples that do not fall into the "general agreement" category, the most serious discrepancy involves two samples where the LC/MS/MS method detected a violative level of a cephalosporin beta-lactam (deacetylcephapirin) in the first sample and a possibly violative level of desfuroylceftiofur in the second, whereas the microbial assay identified the two samples as having only violative levels of a penicillin beta-lactam.

Liquid chromatographic analysis of incurred amoxicillin residues in catfish muscle following oral administration of the drug.

Improper application of antibiotic chemicals to livestock and aquaculture species may lead to the occurrence of residues in food supplies. An appropriate depletion period is needed after the administration of drugs to animals for ensuring that residues in edible tissues are below established tolerance levels. This study was conducted to determine incurred amoxicillin residues in catfish muscle following oral administration. Dosed fish were harvested after four depletion periods, and muscle fillets were analyzed for amoxicillin residues using an HPLC method with precolumn derivatization and fluorescence detection. The residue levels in fish after a 6-h depletion ranged from 40 to 64 ng/g with one exception at 297 ng/g. Average residue levels decreased to 5.4 and 2. 8 ng/g after 24- and 48-h depletions, respectively. Residue levels after a 72-h depletion decreased to below the method's limit of quantitation (1.2 ng/g). An LC-MS/MS confirmatory method was developed. Confirmation of the presence of amoxicillin was demonstrated in incurred fish samples containing residues at approximately 50-300 ng/g.

Faunal indicator taxa selection for monitoring ecosystem health

Maintaining healthy ecosystems is a prerequisite for conserving biodiversity. The complex nature of ecosystems often necessitates the use of indicator taxa to monitor ecosystem health. However, ambiguous selection criteria and the use of inappropriate taxa have brought the utility of indicator taxa under question. This review compiles existing selection criteria from the literature, evaluates inconsistencies among these criteria, and proposes a step-wise selection process. In addition, 100 vertebrate and 32 invertebrate taxa documented in the conservation science literature as indicators of ecosystem health are examined to assess how well they adhere to the referenced criteria. Few vertebrate taxa fulfill multiple criteria, as most are highly mobile generalists that lack established tolerance levels and correlations with ecosystem changes. Most suggested invertebrate taxa also lack correlations to ecosystem changes, but satisfy other selection criteria. However, invertebrate taxa are often suggested at high taxonomic levels, encompassing many species, making it difficult to measure specific attributes, and potentially including many unnecessary and even inappropriate species.

Local temperature and pressure variations and its effects on daily ionometric measurements of radiation beam outputs from linear accelerators

As part of the quality assurance protocol for linear aceelerators at West Virginia University Hospitals, the local temperature and pressure are recorded on a daily basis by the radiation therapists. These temperature and pressure values are not used for temperature and pressure correction unless the ionometric measurements of radiation beam outputs from linear accelerators are outside the established tolerance levels. This paper presents a study on the variation of temperature and pressure over the past two years. Analysis of the data showed that the variation of pressure is within ± 1.5% of the average value. Likewise, the variation of temperature is within ±1.5% of the average value. The worst possible effects of temperature and pressure on ionometric measurements would be within ±3%, which is at the tolerance levels recommended by the American Association of Physicists in Medicine (AAPM) Task Group No. 13. By maintaining machine output fluctuation to within ±2%, the maximum deviation of uncorrected ionometric measurements would be within ±5%. This study collaborates with the tolerance levels suggested by the AAPM Task Group No. 40.

Effects of water deprivation on feed utilization and mineral balances in sheep drinking natural saline well water

The present trials dealt with the combined effect of water salinity and infrequent water intake, once every 72 hours, in two groups of rams fed roughage diets at the maintenance level of digested protein intake, compared with sheep offered fresh tap water daily as controls. The results indicated that daily watered sheep responded favourably to drinking saline well water in terms of performance and weight gain, as well as nitrogen and mineral balances. Intermittent saline water intake, on the other hand, seemed to affect all characteristics studied adversely. The animals lost weight, digestive capacity was reduced and, therefore, DOM and DCP intakes decreased significantly. Nitrogen and sodium balances became negative, and the other mineral balances were also adversely affected. Further experiments are needed, particularly to re-evaluate established tolerance levels (1·3% NaCl) which may differ according to types of salts in the well water and also under conditions of long adaptation to water deprivation.

Investigation of carbofuran and its metabolites by gas-liquid chromatography in green and dry hops

Processed hop cones (Humulus americanus) are an important flavoring component in beer, and it is possible that carbofuran and its metabolites could be found in treated hops and thus in beer. Hop cones were treated with 1.12 kg/ha active ingredient carbofuran (2, 3-dihydro-2, 2-dimethyl-7-benzofuranyl-N-methyl carbamate) for the control of root weevils (Otiorhynchus sulcatus, O. ovatus). The carbamates in the cones were determined using gas-liquid chromatography (GLC) and a thermionic specific detector. The percent recoveries for the carbamates ranged from 88.7 ± 5.3 to 95.3 ± 6.3% (green hops) and from 88.6 ± 12.3 to 98.0 ± 5.0% (dry hops). The phenolic metabolites were analyzed as their 2, 4-dinitrophenol ether derivatives, using GLC with an electron capture detector. The percent recoveries ranged from 85.0 ± 5.8 to 88.3 ± 8.5% (green hops) and from 80.3 ± 4.4 to 95.3 ± 3.0% (dry hops). The GLC procedure was sensitive to 0.05 ppm. Control samples in all cases contained less than 0.05 ppm and green, treated hop cones had residues of less than 0.05 ppm. Dry treated hop cones contained less than 0.05 ppm of all chemicals, except 3-keto-7-phenol (0.12 ppm) and the 3,7-diol (0.07 ppm). Although the U.S. Environmental Protection Agency (EPA) has not established tolerance levels for carbofuran and its metabolites in hop cones, the present investigation shows that residue levels on green and dry hop cones are well below the EPA's tolerances for carbofuran in other commodities.

INVESTIGATION OF CARBOFURAN AND ITS METABOLITES BY GAS-LIQUID CHROMATOGRAPHY IN GREEN AND DRY HOPS

Processed hop cones (Humulus americanus) are an important flavoring component in beer, and it is possible that carbofuran and its metabolites could be found in treated hops and thus in beer. Hop cones were treated with 1.12 kg/ha active ingredient carbofuran (2, 3-dihydro-2, 2-dimethyl-7-benzofuranyl-N-methyl carbamate) for the control of root weevils (Otiorhynchus sulcatus, O. ovatus). The carbamates in the cones were determined using gas-liquid chromatography (GLC) and a thermionic specific detector. The percent recoveries for the carbamates ranged from 88.7 ± 5.3 to 95.3 ± 6.3% (green hops) and from 88.6 ± 12.3 to 98.0 ± 5.0% (dry hops). The phenolic metabolites were analyzed as their 2, 4-dinitrophenol ether derivatives, using GLC with an electron capture detector. The percent recoveries ranged from 85.0 ± 5.8 to 88.3 ± 8.5% (green hops) and from 80.3 ± 4.4 to 95.3 ± 3.0% (dry hops). The GLC procedure was sensitive to 0.05 ppm. Control samples in all cases contained less than 0.05 ppm and green, treated hop cones had residues of less than 0.05 ppm. Dry treated hop cones contained less than 0.05 ppm of all chemicals, except 3-keto-7-phenol (0.12 ppm) and the 3,7-diol (0.07 ppm). Although the U.S. Environmental Protection Agency (EPA) has not established tolerance levels for carbofuran and its metabolites in hop cones, the present investigation shows that residue levels on green and dry hop cones are well below the EPA's tolerances for carbofuran in other commodities.

Occurrence and Methods of Control of Chemical Contaminants in Foods

Contamination of food by chemicals can result from their use on agricultural commodities; accidents or misuse during food handling and processing; nucler weapon testing and operation of nuclear power plants; and disposal of industrial chemicals or by-products with subsequent dispersal into the environment. The Food and Drug Administration (FDA), as the Federal agency mainly responsible for evaluating the hazards of chemical contaminants and enforcing any established tolerance levels for them in foods, has been monitoring pesticides, industrial chemicals, metals, and radionuclides in foods in its nationwide programs for many years. In addition, FDA searches for potential contaminants among the approximately 50,000 industrial chemicals manufactured in the United States and coordinates its efforts with those of other Federal and state agencies in these investigations. The overall results of the FDA surveillance and compliance programs for chemical contaminants in foods, as well as specific examples illustrating the wide range of incidents and types of occurrences, are presented.

Occurrence and methods of control of chemical contaminants in foods.

Contamination of food by chemicals can result from their use on agricultural commodities; accidents or misuse during food handling and processing; nucler weapon testing and operation of nuclear power plants; and disposal of industrial chemicals or by-products with subsequent dispersal into the environment. The Food and Drug Administration (FDA), as the Federal agency mainly responsible for evaluating the hazards of chemical contaminants and enforcing any established tolerance levels for them in foods, has been monitoring pesticides, industrial chemicals, metals, and radionuclides in foods in its nationwide programs for many years. In addition, FDA searches for potential contaminants among the approximately 50,000 industrial chemicals manufactured in the United States and coordinates its efforts with those of other Federal and state agencies in these investigations. The overall results of the FDA surveillance and compliance programs for chemical contaminants in foods, as well as specific examples illustrating the wide range of incidents and types of occurrences, are presented.