Mustafa I. Selim

Assessing airborne aflatoxin B1 during on-farm grain handling activities

The presence of aflatoxin in corn and corn dust during relatively normal years and the increased risk of Aspergillus flavus infestation during drought conditions suggest that airborne agricultural exposures should be of considerable concern. Liquid extraction, thin layer chromatography, and high pressure liquid chromatography were used for the analysis of aflatoxin B1 in grain dust and bulk corn samples. A total of 24 samples of airborne dust were collected from 8 farms during harvest, 22 samples from 9 farms during animal feeding, and 14 sets of Andersen samples from 11 farms during bin cleaning. A total of 14 samples of settled dust and 18 samples of bulk corn were also collected and analyzed. The airborne concentration of aflatoxin B1 found in dust collected during harvest and grain unloading ranged from 0.04 to 92 ng/m3. Higher levels of aflatoxin B1 were found in the airborne dust samples collected from enclosed animal feeding buildings (5-421 ng/m3) and during bin cleaning (124-4849 ng/m3). Aflatoxin B1 up to 5100 ng/g were detected in settled dust collected from an enclosed animal feeding building; however, no apparent correlation was found between the airborne concentration of aflatoxin B1 and its concentration in settled dust or bulk corn. The data demonstrate that farmers and farm workers may be exposed to potentially hazardous concentrations of aflatoxin B1, particularly during bin cleaning and animal feeding in enclosed buildings.

Dermatitis among automobile production machine operators exposed to metal‐working fluids

This cross-sectional study was designed to assess differences in prevalence of contact dermatitis between machine operators exposed to metal-working fluids (MWFs) and unexposed assemblers, and to assess potential risk factors for contact dermatitis among these machine operators. In their work, machine operators were exposed to either semisynthetic or soluble oil MWFs. We evaluated 158 machine operators and 51 assemblers from one large automobile transmission plant using questionnaires, dermatologist examination of the skin, and dermal dosimetry to measure wetness and metal exposures. We found that machine operators had more combined (definite plus possible) dermatitis (27.2% vs. 13.7%, chi(2) = 3.9, p = 0.05, 1 df) compared with assemblers. Among machine operators, risk factors significantly associated with (combined) dermatitis were subjective assessment of wetness of the work, exposure to semisynthetic as opposed to soluble oil MWF, current cigarette smoking, and increasing worker age. These risk factors suggested preventive and control measures including control of wet work, surveillance program including early self-report of dermatitis, consideration of replacement of semisynthetic with soluble oil MWFs, and strictly limiting smoking among machine operators exposed to MWFs.

Exposure While Applying Industrial Antimicrobial Pesticides

Forty-three assessments were made of dermal and/or inhalation chemical exposure while applying industrial antimicrobial pesticide products, either by manually pouring or pumping liquids or by pouring a solid (powder or flake) product. Inhalation exposure was assessed via a personal air sample but was usually below the chemical limit of detection. Dermal exposure outside work clothing and dermal deposition inside the clothing was assessed via dermal gauze dosimeters. While dosimeters at discrete body locations often received exposures below the limit of detection, one or more dosimeters on individual applicators almost always showed measurable exposure. The median measured dose was between 30% and 70% of the maximum credible summed dose calculated by assuming that each dosimeter showed either the level of measurable deposition or one-half of the detection limit at locations where the chemical was unmeasurable. Because of differences in settings and the low level of control implicit in these application processes, measurable dermal doses were highly variable. Mean measurable dose rates were near 3, 8, and 10 mg product/hr, and daily total deposited doses were 2, 3.5, and 5 mg of product for pouring and pumping liquids and for pouring solids, respectively. Although the effect of gloves cannot be directly determined, wearers of gloves had geometric mean hand total doses 155- to 290-fold less than those not wearing gloves. Similar to the statistics for agricultural pesticides, the dermal route of exposure for these industrial pesticides exceeds the inhalation route by 5X to 100X, depending on assumptions regarding nondetectable values.

Laboratory Comparison of Vacuum, OSHA, and HUD Sampling Methods for Lead in Household Dust

The goals of this project were to evaluate and compare the efficiency and reproducibility of three methods for sampling lead-containing dust in homes. Lead-containing dust was generated in a 1-m3 chamber and uniformly deposited onto surfaces typically found in the home (painted wood, unpainted wood, varnished wood, linoleum, and carpet). Trials with three levels of lead concentrations were performed for each surface. Replicate, side-by-side, surface samples were collected using the Occupational Safety and Health Administration (OSHA) wipe method, the Department of Housing and Urban Development (HUD) wipe method, and a vacuum-filter method. Samples were digested with nitric acid and analyzed using graphite furnace atomic absorption spectroscopy per National Institute of Occupational Safety and Health Method 7105. Recovery for the HUD method was consistently the highest on most surfaces (linoleum, 89.9 to 108.9%; painted wood, 71.2 to 153.7%; unpainted wood, 25.3 to 76.0%; varnished wood, 8.7 to 165.6%). On carpet the vacuum method had a significantly higher recovery (26.2 to 47.8%). For all sampling methods the percent recovery depended on type of surface and lead concentration. The reproducibility of percent recovery for the HUD (pooled coefficient of variation [CV] = 0.22) and OSHA (pooled CV = 0.27) methods was lower than that of the vacuum method (pooled CV = 0.46), though not statistically significant. Reproducibility for all methods did not vary significantly over surface type or lead concentration. Overall, the HUD method yielded the most accurate measurements, with recoveries closest to 100%. It was also more durable than the OSHA method, where Whatman filters were observed to tear.

Pesticide contamination of private well water, a growing rural health concern

The Iowa Statewide Rural Well Water Survey (SWRL) was conducted between April 1988 and June 1989. SWRL was designed to provide a statistically valid assessment of the proportion of private rural wells and rural Iowa residents affected by various environmental contaminants. The survey was a systematic sample, stratified by rural population density. Approximately 14% of wells had detections of pesticides: 16 pesticide compounds (mostly herbicides) were detected, including 11 parent compounds and 5 environmental metabolites; 16 pesticides (mostly insecticides) were not detected. Atrazine and its metabolites were found in 8% of wells. Multiple residues were detected in all regions of the state. The mean concentrations were generally <1 μg/L. Lifetime Health Advisory Levels (HALs) were exceeded in 1.2% of private, rural wells in Iowa. Detailed evaluations of these sites indicate 25% are caused by point source contamination (spill and back-siphoning), while the majority, 62.5%, appear to be nonpoint sources related to normal agricultural practices. Statistical analyses show significant associations between many water quality parameters tested during SWRL, but the associations are not strong predictors based on state-wide data. By far the most significant factor explaining water quality variations is well depth.

Supercritical fluid extraction of aflatoxin B1 from soil

This research describes the development of a supercritical fluid extraction (SFE) method to recover aflatoxin B(1) from fortified soil. The effects of temperature, pressure, modifier (identity and percentage), and extraction type were assessed. Using the optimized SFE conditions, the mean recovery from air dried soil was 72%. The variables associated with changes in recovery of aflatoxin were co-solvents, static extraction, and temperature. Acetonitrile-2% acetic acid, used both in-cell and on-line, provided the most efficient recovery. The results indicate that desorption from the soil was the limiting factor in recovery and that the static phase was more important than the dynamic.

DEVELOPMENT AND OPTIMIZATION OF A SUPERCRITICAL FLUID EXTRACTION METHOD FOR THE ANALYSIS OF AFLATOXIN B1 IN GRAIN DUST

A new method for the extraction of aflatoxins from small quantities of airborne dust, using supercritical carbon dioxide, is described. The efficacy of this method is compared with a previously used liquid extraction procedure, using naturally contaminated grain dust samples. Supercritical fluid extraction (SFE) provides faster, more sensitive, and more selective extraction, compared with the liquid extraction method. The optimized SFE conditions for 0.1-1.2 g of dust in a 2.5 mL extraction chamber are: 2000 psi, 40 degrees C, 15 mL of liquid CO2, static extraction for 15 min, and 250 microL of acetonitrile added to sample in the extraction chamber. A detection limit of 1 ng aflatoxin B1 per sample is obtained using off-line HPLC analysis with UV detection. Lower detection limits are obtained using on-line SFE and HPLC analysis with fluorescence detection.

Effect of dietary acids on the formation of aflatoxin B2a as a means to detoxify aflatoxin B1

ABSTRACT Aflatoxin B1 (AFB1) is a class 1 carcinogen and a common food contaminant worldwide with widely uncontrolled human exposure. The ability of organic acids to transform AFB1 into a known detoxified form, aflatoxin B2a (AFB2a), was investigated using high performance liquid chromatography-electrospray ionisation-time of flight mass spectrometry (HPLC/ESI/TOF/MS). The identity of the transformation product was confirmed by accurate mass measurement, chromatographic separation from other aflatoxins, H1-nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy. Of the weak acids tested, citric acid was found to be the most effective for AFB2a formation. At room temperature, 1 M citric acid was able to convert > 97% of AFB1 to AFB2a over 96 h of treatment. Up to 98% transformation was achieved by boiling AFB1 in the presence of citric acid for 20 min. AFB1 hydration after ingestion was explored by spiking AFB1 into simulated gastric fluid containing citric acid. Under these conditions, > 71% of AFB1 was hydrated to AFB2a and did not show any reversion to the parent compound after being transferred to a neutral solution. These results provide a basis for a practical and effective method for detoxification of AFB1 in contaminated foods.

Adduction to arginine detoxifies aflatoxin B1 by eliminating genotoxicity and altering in vitro toxicokinetic profiles

Aflatoxin B1 (AFB1), a class 1 carcinogen and prominent food contaminant, is highly linked to the development of hepatocellular carcinoma (HCC) and plays a causative role in a large portion of global HCC cases. We have demonstrated that a mixture of common organic acids (citric and phosphoric acid) along with arginine can eliminate >99% of AFB1 in solution as well as on corn kernels and convert it to the AFB2a-Arg adduct, acting as a potential detoxification process for contaminated foods. Evaluation of toxicokinetic changes after AFB2a-Arg formation show that the product is highly stable in biological fluids, is not metabolized by P450 enzymes, is highly plasma protein bound, has low lipid solubility, and has poor intestinal permeability/high intestinal efflux compared to AFB1. Ames’ test results show that at mutagenic concentrations of AFB1, AFB2a-Arg does not have any measurable mutagenic effect which was confirmed by DNA adduct identification by liquid chromatography-mass spectrometry. Evaluation in HepG2 and HepaRG cells showed that AFB2a-Arg did not cause any significant decreases in cell viability nor did it increase micronuclei formation when administered at toxic concentrations of AFB1. These results show that conversion of AFB1 to AFB2a-Arg is a potential strategy to detoxify contaminated foods.

A new method for simultaneous analysis of semi-volatile organic compounds in outdoor/indoor air of large office buildings

Exposure to various groups of SVOCs, particularly in the indoor air, is of increasing concern worldwide. These groups include PAHs, PCBs, phthalate esters, organochlorines, and many others, which are classified among the priority organic pollutants. A new method was developed and optimized for simultaneous whole air sampling using recent canister/helium diffusion technology followed by online cryogenic trapping, concentration of the SVOCs, and direct on-column injection into the GC/MS. The method was optimized using 25 SVOCs (seven of PAHs, eight of PCBs, four of phthalates, three OCs, and three of others) and tested in the analysis of 294 air samples, which were collected from the outdoor and the indoor at eight large office buildings on 21 different dates from January 2011 to August 2011. The method detection limits ranged from 0.05 ppbv for 2,4-dinitrobenzene to 2.6 ppbv for chrysene. Phthalates were the most abundant among other SVOCs, whereas fluorine and dichlorobiphenyl were the most abundant among the PAHs and PCBs, respectively. The I/O ratios of most SVOCs were < 1, indicating that the outdoor air was the main source of indoor pollutants. The method demonstrated: (1) accurate and efficient for various SVOCs determination, which allowed assessment of the factors affecting their levels in the sampling locations, and (2) the capability of reliable use of recent technology which eliminates the disadvantages of using sorbents and solvents by the current methods.