Disposition of [14C]-polystyrene microplastics after oral administration to lactating sheep.

Microplastics have become a ubiquitous contaminant, but their fate in food animals is largely unknown. In this study, [14C]-polystyrene microplastic (PS-MP) particles were orally dosed to lactating sheep to evaluate their absorption and disposition. Elimination of the [14C]-PS-MP was predominately through faeces with faecal radioactivity peaking at 24 h post-dosing but continuing to be present throughout the entire 72 h study period. Only a small fraction (≤ 1%) of the dosed [14C]-PS-MP was present in blood, milk, and urine. Pharmacokinetic analysis of blood plasma radioactivity, using non-compartment modeling, indicated rapid absorption (T1/2 0.4 to 3 h) with slow elimination (T1/2 37 to 48 h). Radioactivity in milk and urine had similar elimination patterns with radiocarbon activities peaking 24 h post-dosing with detectable elimination throughout the 72 h study period. No radioactivity was quantifiable in tissues at the 72 h withdrawal period.

Comparison of immunoassay and LC-tandem mass spectrometry analyses of ractopamine in hog oral fluid.

The accurate detection of ractopamine in food animals is crucial for marketing since some entities require animals or animal carcasses to be free of ractopamine residues. Field-based ractopamine screening tests that are rapid, sensitive, and capable of high-throughput are highly desirable to ensure that inadvertent exposure to ractopamine did not occur in animals marketed as animals that have not been fed ractopamine. An immunochemically based lateral flow assay was used to analyze oral fluids from hogs never exposed to ractopamine and from hogs that were presumed positives and results were confirmed using an enhanced sensitivity LC-MSMS method. We found that an immunochemically based lateral flow system having a working range of 2.5 to 15 ng mL-1 worked well as a screening assay with 1.7% false positive results in freshly collected hog oral fluids. Using ractopamine glucuronide standards and LC-MSMS, we determined that the false positive results were not due to the presence of ractopamine glucuronide metabolites in oral fluids.

Effects of polystyrene micro/nanoplastics on liver cells based on particle size, surface functionalization, concentration and exposure period.

Micro/nanoplastics (MP/NP) contaminate our food and drinking water but their impact on human health has not been well-documented. The liver is one of the first organs that ingested MP/NP encounter and it has a major role in the clearance of xenobiotics. Therefore, the effects of polystyrene MP/NP on liver HepG2 cells were studied. Cellular responses to particles of various sizes (50-5000 nm) and surface functionalization (aminated, carboxylated or non-functionalized) were determined at different concentrations (0.1-100 µg/mL) and exposure periods (1-24 h). Smaller sized particles were internalized by HepG2 cells more avidly than larger particles regardless of functionalization; the highest uptake being for 50 and 100 nm aminated particles at lower concentrations. Confocal microscopy images of cells corroborated quantitative uptake results. Aminated particles were more toxic to the cells than carboxylated or non-functionalized particles. Among aminated particles smaller particles (50 and 100 nm) were more detrimental to cell viability compared to larger particles (1000 or 5000 nm) with toxicity increasing with concentration. Treatment with the particles for 4 h increased intracellular concentrations of Caspase-3 by 1.5-2.8 fold, but 24 h exposure to the particles attenuated this increase in Caspase-3 concentrations. A slight trend of higher Caspase-3 concentration in cells treated with larger particles (500-5000 nm) compared to smaller particles (50-200 nm) was observed, indicating that larger particles are more likely to direct cells toward apoptotic cell death upon 4 h exposure. Exposure of cells to large PS particles (500-5000 nm) upregulated interleukin-8 and the effect was enhanced at 24 h. Overall, the study demonstrated that smaller aminated particles were most toxic to hepatocytes, but larger particles induced apoptotic cell death or an inflammatory response depending on the length of exposure.

Performance of allergen testing in a survey of frozen meals and meals ready-to-eat (MREs).

A 7-plex immunoassay capable of detecting cashew, egg, hazelnut, milk, peanut, shrimp, and soy allergens was used to screen meals ready-to-eat (MREs) and frozen meals that contained meat or poultry. The same food matrices were also evaluated using single individual allergen immunoassays. Multiplex and single allergen test results were compared with the allergen declared on the food label, which was considered the standard. For both the frozen meals (n = 113) and MREs (n = 24) each analytical method failed to detect allergens that were declared on product labels, but only in frozen meals were allergens detected that were not declared on the label. Undeclared allergens were detected for egg in 1.8% (2/113) and for soy in 7.1% (8/113) of frozen meals. Labelled allergens were not detected in 0.9% (1/113) of milk, 4.4% (5/113) of egg, and 15% (17/113) of soy allergens in frozen meals. Assay performance for evaluating allergens in MREs was poor.

Assessment of veterinary drugs present in pork kidney from a Midwest US retail market.

A total of 1040 pork kidneys were purchased from 4 retail stores located in a Midwestern US town and screened for antibiotics with the Charm-KIS™ screening test. Six samples (0.6%) tested positive with the Charm-KIS™. Sixty-five samples from each retail location and the 18 Charm-KIS™ positive or 'caution' samples were also subjected to ELISA to determine the presence of commonly used veterinary drugs including flunixin, ractopamine, sulfamethazine, and/or tetracycline of the 278 samples assessed by ELISA, flunixin, ractopamine, sulfamethazine, and tetracycline residues were found to be 0%, 22%, 4%, and 10% ELISA positive respectively, and had greater than limit of quantitation concentrations as measured by LC-MS/MS.  All residue levels determined by LC-MS/MS were well below US tolerances, regardless of analyte.  These findings suggest that veterinary drugs are being used in accordance with US regulations and that veterinary drug residues in pork do not pose a health concern to US consumers.