Polybrominated diphenyl ethers: causes for concern and knowledge gaps regarding environmental distribution, fate and toxicity

This manuscript critically considers several areas of study of the polybrominated diphenyl ether compounds. Specifically, a brief review of PBDE toxicity is followed by an in depth discussion of PBDE occurrence in abiotic and biotic environmental matrices. Temporal and geographic trends are examined in conjunction with risk assessment factors. Rather than summarize or tabulate the growing body of literature on PBDEs in the environment, the overall goal of this review paper is to highlight broad patterns that may contribute to a more holistic understanding of PBDE behavior in the environment, as well as to identify critical areas of research that warrant further attention.

Characterization of selenium species in Brazil nuts by HPLC-ICP-MS and ES-MS

Brazil nuts have been classified as the foodstuffs that contain the highest level of unadulterated selenium, an essential trace element that appears to prevent cancer. To date, characterization of the selenium species in brazil nuts has not yet been investigated. In this work, various sample preparation approaches, including microwave extractions and enzymatic treatments, are examined with the goal of species preservation and subsequent selenium speciation; of these approaches, an enzymatic treatment with Proteinase K proved most effective. High-performance liquid chromatography (HPLC) separation strategies and inductively coupled plasma mass spectrometry (ICP-MS) detection schemes will also be presented. Extracts are evaluated against available standards for the commercially obtainable seleno-amino acids, selenomethionine (SeMet), selenoethionine (SeEt), and selenocystine (SeCys); selenomethionine was demonstrated to be the most abundant of these seleno-amino acids. Further characterization of unidentified selenium-containing peaks is attempted by the employment of several procedures, including electrospray-mass spectrometry (ES-MS). A peptide structure was identified; however, this was considered a tentative proposal due to the large background produced by the extremely complicated brazil nut matrix.

HPLC-ICP-MS determination of selenium distribution and speciation in different types of nut

In addition to determination of total selenium in nuts, the element distribution among different fractions (lipid extract, low molecular weight, and protein fractions), and speciation analysis were studied. Improved precision for total selenium determination was observed after elimination of lipids. Because selenium was not detected in any of the lipid extracts obtained from the different types of nuts (ICP-MS), in each determination and/or speciation procedure used in this work lipids were extracted (chloroform-methanol, 2:1) and discarded before analysis. In agreement with previously reported data, high selenium levels were found in Brazil nuts (those purchased without shells contained approximately a quarter the content than those purchased with shells) and significantly lower levels in walnuts, cashews, and pecans nuts. Low-molecular-weight compounds were extracted with perchloric acid (0.4 mol L(-1)) to furnish a fraction containing 3 to 15% of the total selenium in different types of nuts. The proteins were isolated from nut samples by dissolution in 0.1 mol L(-1) sodium hydroxide and subsequent precipitation with acetone. They were then dissolved in phosphate buffer pH 7.5. Analysis of protein fractions focused on selenium in two possible states - weakly and firmly bound to proteins. Results obtained for Brazil nuts by size-exclusion chromatography with on-line ICP-MS detection, in the absence and in the presence of beta-mercaptoethanol, showed that approximately 12% of total selenium was weakly bound to proteins. To obtain information about firmly bound selenium, the protein extracts were hydrolyzed enzymatically with proteinase K. Speciation was performed by means of ion-pairing HPLC-ICP-MS. The primary species found in all types of nuts was Se-methionine (19-25% of total selenium for different types of nuts).

Solid-phase microextraction as a sample preparation strategy for the analysis of seleno amino acids by gas chromatography-inductively coupled plasma mass spectrometry

Solid-phase microextraction (SPME) is used as a sample preparation strategy for gas chromatographic (GC) analysis of the seleno amino acids, selenomethionine (SeMet), selenoethionine (SeEt) and selenocystine (SeCys). Acylation of the amino group and esterification of the carboxylic group in these compounds was performed with isobutylchloroformate to increase volatility. The amino acid derivatives were then extracted by silica fibers with polydimethylsiloxane (PDMS) coatings prepared by the sol-gel process. Investigations of extraction time, acid and salt addition, and polymer length (for the sol-gel process) were conducted with the goal of procedural optimization. Initial characterizations were conducted using gas chromatography with flame ionization detection (GC-FID). Inductively coupled plasma mass spectrometric detection was employed for final selenium detection. Sub-ppb detection limits were obtained for all analytes although relative standard deviations were higher than those typically obtained in solid-phase microextraction.

Effect of arsenic on benzo[a]pyrene DNA adduct levels in mouse skin and lung

Concomitant exposures to arsenic and polycyclic aromatic hydrocarbons (PAHs) such as benzo[a]pyrene (BaP) are widespread. While BaP acts by binding to and inducing mutations in critical sites on DNA, the mechanism(s) of arsenic carcinogenesis remains unknown. Data from epidemiological studies of arsenic copper smelter workers and arsenic ingestion in drinking water suggest a positive interaction for arsenic exposure and smoking and lung cancer. A previous in vitro study showed that arsenic potentiated the formation of DNA adducts at low doses of BaP and arsenic. The present study was conducted to test the effect of arsenic on BaP-DNA adduct formation in vivo. We hypothesized that arsenic co-treatment would significantly increase BaP adduct levels in C57BL/6 mouse target organs: skin and lung. Treatment groups were: five mice, -BaP/-arsenic; five mice, -BaP/+arsenic; 15 mice, +BaP/-arsenic; 15 mice, +BaP/+arsenic. Mice in the appropriate groups were provided sodium arsenite in drinking water (2.1 mg/l), ad libitum, for 13 days (starting 9 days before BaP treatment), and 200 nmol BaP/25 ml acetone (or acetone alone) was applied topically, once per day for 4 days. DNA was extracted from skin and lung and assayed by (32)P-postlabeling. Statistical comparisons were made using independent t-tests (unequal variances assumed). BaP-DNA adduct levels in the +BaP groups were significantly higher than -BaP controls. Arsenic co-treatment increased average BaP adduct levels in both lung and skin; the increase was statistically significant in the lung (P = 0.038). BaP adduct levels in the skin of individual animals were positively related to skin arsenic concentrations. These results corroborate our in vitro findings and provide a tentative explanation for arsenic and PAH interactions in lung carcinogenesis.

A study of method robustness for arsenic speciation in drinking water samples by anion exchange HPLC-ICP-MS

Regulating arsenic species in drinking waters is a reasonable objective, since the various species have different toxicological impacts. However, developing robust and sensitive speciation methods is mandatory prior to any such regulations. Numerous arsenic speciation publications exist, but the question of robustness or ruggedness for a regulatory method has not been fully explored. The present work illustrates the use of anion exchange chromatography coupled to ICP-MS with a commercially available "speciation kit" option. The mobile phase containing 2 mM NaH(2)PO(4) and 0.2 mM EDTA at pH 6 allowed adequate separation of four As species (As(III), As(V), MMAA, DMAA) in less than 10 min. The analytical performance characteristics studied, including method detection limits (lower than 100 ng L(-1) for all the species evaluated), proved the suitability of the method to fulfill the current regulation. Other parameters evaluated such as laboratory fortified blanks, spiked recoveries, and reproducibility over a certain period of time produced adequate results. The samples analyzed were taken from water utilities in different areas of the United States and were provided by the U.S. EPA. The data suggests the speciation setup performs to U.S. EPA specifications but sample treatment and chemistry are also important factors for achieving good recoveries for samples spiked with As(III) as arsenite and As(V) as arsenate.

Robust properties of membrane-embedded connector channel of bacterial virus phi29 DNA packaging motor

Biological systems contain highly-ordered macromolecular structures with diverse functions, inspiring their utilization in nanotechnology. A motor allows linear dsDNA viruses to package their genome into a preformed procapsid. The central component of the motor is the portal connector that acts as a pathway for the translocation of dsDNA. The elegant design of the connector and its channel motivates its application as an artificial nanopore (Nature Nanotechnology, 4, 765-772). Herein, we demonstrate the robust characteristics of the connector of the bacteriophage phi29 DNA packaging motor by single pore electrophysiological assays. The conductance of each pore is almost identical and is perfectly linear with respect to the applied voltage. Numerous transient current blockade events induced by dsDNA are consistent with the dimensions of the channel and dsDNA. Furthermore, the connector channel is stable under a wide range of experimental conditions including high salt and pH 2-12. The robust properties of the connector nanopore made it possible to develop a simple reproducible approach for connector quantification. The precise number of connectors in each sheet of the membrane was simply derived from the slopes of the plot of voltage against current. Such quantifications led to a reliable real time counting of DNA passing through the channel. The fingerprint of DNA translocation in this system has provided a new tool for future biophysical and physicochemical characterizations of DNA transportation, motion, and packaging.

Investigation of selenium-containing root exudates of Brassica juncea using HPLC-ICP-MS and ESI-qTOF-MS

Selenium-containing root exudates were investigated in a known selenium accumulator model plant. Indian mustard (Brassica juncea) plants were grown hydroponically and supplemented with selenite (SeO(3)(2-)) in a 25% Hoagland's nutrient solution. Additive concentrations were 0, 1, 5 and 20 microg mL(-1) Se with five replicate plants per treatment level. Plants were exposed to the respective Se solutions for two weeks, then placed in deionized water for two more weeks. The hydroponic solutions were collected for analysis after the first two weeks of selenium supplementation (day 14) and twice during the deionized water period (days 21 and 28). Separation by ion-pairing high performance liquid chromatography was followed by inductively coupled plasma-mass spectrometry (ICP-MS) for selenium specific detection. Chromatographic peaks unable to be identified by retention-time matching were collected for analysis by electrospray ionization mass spectrometry (ESI-MS). Additional chemical experiments were performed for structural elucidation. Several selenium-containing compounds were identified in the exudate-containing solution and two were identified as selenocystine and the selenosulfate (SSeO(3)(2-)) ion. The presence of dimethylselenide (CH(3)SeCH(3)) is also observed but cannot be attributed exclusively to plant exudation because plants were not grown in sterile conditions. Further, the incorporation of fortified selenoamino acids into peptide structures was found to occur under neutral pH conditions, suggesting that exuded enzymes might facilitate such a reaction. Finally, physiological differences resulting from selenium supplementations were noted and discussed.

Retention of Cr(III) by high-performance chelation ion chromatography interfaced to inductively-coupled plasma mass spectrometric detection with collision cell

High-performance chelation ion chromatography (HPCIC) was employed to retain cationic Cr(III) on an anion-exchange column and hence allow the separation of the two most prevalent forms of chromium, Cr(II) and Cr(VI). A mobile phase of nitric acid was utilized at pH = 1.5; additionally, 2,6-pyridinedicarboxylic acid was used at a concentration of 6 mM. Additives with different structural characteristics were used in an effort to elucidate retention mechanisms. Inductively-coupled plasma mass spectrometry was used for chromium detection. A collision cell was utilized to reduce chloride-based polyatomic ions that may interfere with the detection of Cr(III), and a detection limit study yielded levels in the low part-per-billion range. The newly developed method was applied to the chromatographic analysis of samples of an incubation medium containing Cr(VI) incubated with cell nuclei.

An HPLC-ICP-MS technique for determination of cadmium-phytochelatins in genetically modified Arabidopsis thaliana

A reversed-phase high-performance liquid chromatographic technique was developed to separate cadmium-phytochelatin complexes (Cd-PC2, Cd-PC3, and Cd-PC4) of interest in the plant Arapidopsis thaliana. High-performance liquid chromatography (HPLC) was coupled to an inductively coupled plasma mass spectrometric (ICP-MS) system with some modification to the interface. This was done in order to sustain the plasma with optimum sensitivity for cadmium detection in the presence of the high methanol loads used in the gradient elution of the reversed-phase separation. The detection limits were found to be 91.8 ngl(-1), 77.2 ngl(-1) and 49.2 ngl(-1) for Cd-PC2, Cd-PC3, and Cd-PC4 respectively. The regression coefficients (r2) for Cd-PC2 to Cd-PC4 detection ranged from 0.998 to 0.999. The method was then used to investigate the occurrence and effect of cadmium-phytochelatin complexes in wild-type Arabidopsis and a phytochelatin-deficient mutant cad1-3 that had been genetically modified to ectopically express the wheat TaPCS1 phytochelatin synthase enzyme. The primary complex found in both wild-type and transgenic plants was Cd-PC2. In both lines, higher levels of Cd-PC2 were found in shoots than in roots, showing that phytochelatin synthases contribute to the accumulation of cadmium in shoots, in the Cd-PC2 form. Genetic modification did, however, impact the overall accumulation of Cd. Transgenic plants contained almost two times more cadmium in the form of Cd-PC2 in their roots than did the corresponding wild-type plants. Similarly, the shoot samples of the modified species also contained more (by 1.6 times) cadmium in the form of Cd-PC2 than the wild type. The enhanced role of PC2 in the transgenic Arabidopsis correlates with data showing long-distance transport of Cd in transgenic plants. Targeted transgenic expression of non-native phytochelatin synthases may contribute to improving the efficiency of plants for phytoremediation.

Studies of selenium-containing volatiles in roasted coffee

Coffee has been an important and heavily used beverage in many cultures over a long period of time. Although sulfur species have been found to be abundant constituents, no work to date has explored the presence of selenium analogues. Investigation of volatile selenium species from green coffee beans, roasted beans, and brewed coffee drink was performed using solid phase microextraction (SPME) sample preconcentration in conjunction with GC/ICP-MS. Several volatile selenium species at trace levels were detected from roasted coffee beans as well as in the steam from brewed coffee drinks. No detectable selenium (and sulfur) species, however, were found in the headspace of green beans, indicating that selenium-containing volatiles are formed during roasting, as is the case for the sulfur volatiles. Matching standards were prepared and used to identify the compounds found in coffee. Artificial supplementation of the green coffee beans with selenium before roasting was performed to further characterize the selenium-containing volatiles formed during the coffee-roasting process.

Comparing a selenium accumulator plant (Brassica juncea) to a nonaccumulator plant (Helianthus annuus) to investigate selenium-containing proteins

Selenoproteins have been identified in a diverse range of organisms, including bacteria and animals. Their occurrence and role in the plant kingdom are, however, less well-understood. This work investigated the water-soluble selenium-containing proteins extracted from a selenium-accumulating plant species (Brassica juncea) and a nonaccumulator species (Helianthus annuus) exposed to varying forms and concentrations of selenium. Firstly, protein extracts were analyzed by size exclusion chromatography coupled to inductively coupled plasma mass spectrometry; specific detection was achieved by monitoring characteristic isotopes. Then, proteolytic digests of the plant extracts were analyzed by reversed phase chromatography coupled to ICP-MS in order to investigate selenoamino acid and selenopeptide content. Selenomethionine was observed to be the primary constituent of the proteins of the nonaccumulator plant, while selenocystine and selenomethionine were found in the same proportion in the accumulator extract. One main selenium-containing species was present at higher levels in the root digests than in the leaf digests; levels were greater in the nonaccumulator than in the accumulator plant.

Development of an analytical scheme for the determination of pyrethroid pesticides in composite diet samples

Analysis of an individual's total daily food intake may be used to determine aggregate dietary ingestion of given compounds. However, the resulting composite sample represents a complex mixture, and measurement of such can often prove to be difficult. In this work, an analytical scheme was developed for the determination of 12 select pyrethroid pesticides in dietary samples. In the first phase of the study, several cleanup steps were investigated for their effectiveness in removing interferences in samples with a range of fat content (1-10%). Food samples were homogenized in the laboratory, and preparatory techniques were evaluated through recoveries from fortified samples. The selected final procedure consisted of a lyophilization step prior to sample extraction. A sequential 2-fold cleanup procedure of the extract included diatomaceous earth for removal of lipid components followed with a combination of deactivated alumina and C(18) for the simultaneous removal of polar and nonpolar interferences. Recoveries from fortified composite diet samples (10 microg kg(-1)) ranged from 50.2 to 147%. In the second phase of this work, three instrumental techniques [gas chromatography-microelectron capture detection (GC-microECD), GC-quadrupole mass spectrometry (GC-quadrupole-MS), and GC-ion trap-MS/MS] were compared for greatest sensitivity. GC-quadrupole-MS operated in selective ion monitoring (SIM) mode proved to be most sensitive, yielding method detection limits of approximately 1 microg kg(-1). The developed extraction/instrumental scheme was applied to samples collected in an exposure measurement field study. The samples were fortified and analyte recoveries were acceptable (75.9-125%); however, compounds coextracted from the food matrix prevented quantitation of four of the pyrethroid analytes in two of the samples considered.

Molecular genetic and geochemical assays reveal severe contamination of drinking water reservoirs at the ancient Maya city of Tikal

Understanding civilizations of the past and how they emerge and eventually falter is a primary research focus of archaeological investigations because these provocative data sets offer critical insights into long-term human behavior patterns, especially in regard to land use practices and sustainable environmental interactions. The ancient Maya serve as an intriguing example of this research focus, yet the details of their spectacular emergence in a tropical forest environment followed by their eventual demise have remained enigmatic. Tikal, one of the foremost of the ancient Maya cities, plays a central role in this discussion because of its sharp population decline followed by abandonment during the late 9th century CE. Our results, based on geochemical and molecular genetic assays on sediments from four of the main reservoirs, reveal that two of the largest reservoirs at Tikal, essential for the survival of the city during the dry seasons, were contaminated with high levels of mercury, phosphate and cyanobacteria known to produce deadly toxins. Our observations demonstrate severe pollution problems at a time when episodes of climatic aridity were prevalent. This combination of catastrophic events clearly threatened the sustainability of the city and likely contributed to its abandonment.

Fate of pentabrominated diphenyl ethers in soil: abiotic sorption, plant uptake, and the impact of interspecific plant interactions

Polybrominated diphenyl ethers (PBDEs) are potentially harmful and persistent environmental pollutants. Despite evidence that soils are a major sink for PBDEs, little is known regarding their behavior in this medium. An environmentally relevant level of a commercial penta-BDE mixture (75 microg kg(-1)) was added to topsoil, and the extractability of three congeners (BDE-47, -99, and -100) was monitored over 10 weeks in planted and unplanted treatments. The extractability of each congener decreased rapidly in the experimental soil due largely to abiotic sorption to soil particles, which was demonstrated by low PBDE recovery from sterilized and dry soils. Monoculture plantings of zucchini and radish did not affect the recovery of PBDEs from soil. However, PBDE recovery from mixed species plantings was nearly 8 times higher than that of unplanted and monoculture treatments, indicating that interspecific plant interactions may enhance PBDE bioavailablity in soil. Evidence for competitive interactions between the two species was revealed by reduced shoot biomass of zucchini plants in mixed treatments relative to pots containing only zucchini. Both plant species accumulated PBDEs in root and shoot tissue (<5 microg kg(-1) plant tissue). PBDE uptake was higher in zucchini, and translocation of PBDEs to zucchini shoots was congener-specific. Our results suggest that although abiotic sorption may limit the potential for human exposure to PBDEs in soil, plants may increase the exposure risk by taking up and translocating PBDEs into aboveground tissues and by enhancing bioavailability in soil.

Deuterium-Labeling Study of the Hydrogenation of 2-Methylfuran and 2,5-Dimethylfuran over Carbon-Supported Noble Metal Catalysts

2-Methylfuran and 2,5-dimethylfuran were deuterated over Pd and Pt catalysts at 90-220 °C. Furan ring saturation over a Pd/C catalyst occurred at low reaction temperatures, which led to deuterated THFs, followed by progressive D exchange in the THF ring at higher temperatures. Finally, H/D exchange occurred in the methyl groups on the THF ring. Cleavage of the C-O bond also occurred over a Pd/C catalyst at elevated temperatures, which resulted in deuterated ketones, for which all H atoms were exchanged for D. Alcohols were produced over a Pt/C catalyst at low temperatures because they are more stable than the corresponding ketones. D replaced H on all carbon atoms of the furan ring and saturated the O and C atoms of the broken C-O bond in both deuterated 2-pentanol and 2-hexanol. At low temperatures (90-105 °C), all H atoms in the deuterated alcohols were exchanged for D except for the last two hydrogen atoms on the methyl groups.

Use of SEC–ICP–MS with a collision cell for determining the interaction of chromium with DNA extracted from metal-contaminated soils

The potential of chromium to bind to DNA isolated directly from soil microbial communities was investigated in this study. An analytical scheme was developed to distinguish between chromium bound to DNA and its fragments or chromium contained elsewhere in an environmental DNA extract. DNA was extracted from chromium-contaminated soils and purified using DNA clean-up resins. Size-exclusion chromatography was employed due to its advantages in the separation and molecular weight approximation of large biomolecules. It was coupled with two on-line detection systems (spectrophotometric and inductively coupled plasma mass spectrometric) to study the binding of chromium to DNA or other components in a DNA extract. A collision cell was pressurized with helium to remove diatomic and polyatomic interferents resulting from the chosen mobile phase. Chromium peaks were observed in both the large and small molecular weight regions of the chromatogram; to further confirm that the environmentally extracted DNA contained Cr, the subsequently purified DNA was examined for total Cr using flow injection ICP-MS to accommodate small sample volumes. DNA samples isolated from the two soils examined contained 0.5-0.7 ppb Cr, indicating that DNA isolated directly from a chromium-contaminated soil has chromium bound to the nucleic acids.

Management practices and phytoremediation by native grasses

Using native species for phytoremediation may be more ecologically beneficial and cost-effective than monoculture planting approaches. This study evaluated the effect of various soil amendments and management on the potential of Midwestern prairie grasses to remediate field soil contaminated with polycyclic aromatic hydrocarbons (PAHs) and other pollutants. A greenhouse investigation was conducted using six different grass species native to Ohio. Plants were grown in buckets containing topsoil and a layer of field-collected contaminated soil. Buckets were amended with commercial compost, fertilizer, or a combination of both. Replicates were watered every fourth day (frequently) or every sixth day (infrequently). Chlorophyll content were measured monthly for five months during the growing season. After five months, cores were sampled from each treatment and the total petroleum hydrocarbon (TPH) and PAH concentration of the soil determined. Native Ohio grasses reduced TPH contamination at least 87% with frequent irrigation and 90% with infrequent irrigation from buckets containing both compost and fertilizer. PAHs were dissipated to concentrations below detection limit of 1 ppm except for benzo (123) perylene and indeno (123-cd) pyrene. Results of this study suggest that it may be effective to allow contaminated sites to re-vegetate with native grasses.

Carbon Nanotube Fiber Ionization Mass Spectrometry: A Fundamental Study of a Multi-Walled Carbon Nanotube Functionalized Corona Discharge Pin for Polycyclic Aromatic Hydrocarbons Analysis

Mass spectrometry continues to tackle many complicated tasks, and ongoing research seeks to simplify its instrumentation as well as sampling. The desorption electrospray ionization (DESI) source was the first ambient ionization source to function without extensive gas requirements and chromatography. Electrospray techniques generally have low efficiency for ionization of nonpolar analytes and some researchers have resorted to methods such as direct analysis in real time (DART) or desorption atmospheric pressure chemical ionization (DAPCI) for their analysis. In this work, a carbon nanotube fiber ionization (nanoCFI) source was developed and was found to be capable of solid phase microextraction (SPME) of nonpolar analytes as well as ionization and sampling similar to that of direct probe atmospheric pressure chemical ionization (DP-APCI). Conductivity and adsorption were maintained by utilizing a corona pin functionalized with a multi-walled carbon nanotube (MWCNT) thread. Quantitative work with the nanoCFI source with a designed corona discharge pin insert demonstrated linearity up to 0.97 (R²) of three target PAHs with phenanthrene internal standard. Graphical Abstract ᅟ.

Influences on transfer of selected synthetic pyrethroids from treated Formica to foods

Children's unstructured eating habits and activities may lead to excess dietary exposures not traditionally measured by the US Environmental Protection Agency. Influence of these activities on transfer of pesticides from treated Formica to foods was studied. The objective was to perform simulation experiments using four foods (bread, apple slices, bologna, and sugar cookies) exposed to treated Formica after varied time intervals between surface contamination and contact (1, 6, and 24 h) and frequency of contact with and without recontamination. Pesticides investigated included permethrin, bifenthrin, cyfluthrin, cypermethrin, and deltamethrin. Data will be used as input parameters for transfer efficiencies (TEs) within the Children's Dietary Intake Model (CDIM), which predicts total dietary exposure of a child. Pesticide transfer from surfaces to bologna and apples was more efficient than to bread and cookies. For the bread and cookies, all pyrethroids had a TE that ranged from below detectible levels to ≤ 4%. A combined average of 32-64% and 19-43% was transferred to bologna and apples, respectively, for the three contact times for all pyrethroids. The TEs of the varied time intervals indicated that increased time between contamination and contact showed little difference for bologna, bread, and cookies, but a significant difference for apples. As long as pesticide levels are measureable on surfaces in children's eating environment, it can be concluded that transfer of pesticides to foods will take place. Foods' characteristics had an important function in the transfer of pesticides when multiple contacts occurred. Regardless of recontamination, pesticides were efficiently transferred from the treated surface to bologna. The bologna did not reach a saturation point during the contacts. Pesticides were also efficiently transferred to apples, but reached a maximum TE during the second contact. The distribution of activity factors within CDIM needs to reflect the differences in the characteristics of the foods.

Surface-to-food pesticide transfer as a function of moisture and fat content

Transfer of pesticides from household surfaces to foods may result in excess dietary exposure in children (i.e., beyond that inherent in foods due to agricultural application). In this study, transfer was evaluated as a function of the moisture and fat content of various foods. Surfaces chosen for investigation were those commonly found in homes and included Formica, ceramic tile, plastic, carpet, and upholstery fabric. Each surface type was sprayed with an aqueous emulsion of organophosphates, fipronil, and synthetic pyrethroids. In the first phase of the study, multiple foods (apples, watermelon, wheat crackers, graham crackers, white bread, flour tortillas, bologna, fat-free bologna, sugar cookies, ham, Fruit Roll-ups, pancakes, and processed American cheese) were categorized with respect to moisture and fat content. All were evaluated for potential removal of applied pesticides from a Formica surface. In the second phase of the study, representative foods from each classification were investigated for their potential for pesticide transfer with an additional four surfaces: ceramic tile, plastic, upholstery, and carpet. Moisture content, not fat, was found to be a determining factor in most transfers. For nearly all surfaces, more efficient transfer occurred with increased hardness (Formica and ceramic tile). Comparatively, the polymer composition of the plastic delivered overall lower transfer efficiencies, presumably due to an attraction between it and the organic pesticides of interest.