Analysis of Nitrosamines in Cooked Bacon by QuEChERS Sample Preparation and Gas Chromatography–Tandem Mass Spectrometry with Backflushing

Nitrites are added as a preservative to a variety of cured meats, including bacon, to kill bacteria, extend shelf life, and improve quality. During cooking, nitrites in the meat can be converted to carcinogenic nitrosamines (NAs), the formation of which is mitigated by the addition of antioxidants. In the past, the U.S. Department of Agriculture (USDA) Food Safety and Inspection Service (FSIS) monitored NAs in pan-fried bacon, but FSIS terminated monitoring of NAs in the 1990s due to the very low levels found. FSIS recently chose to conduct a risk assessment of NAs in cooked bacon to determine if current levels warrant routine monitoring of NAs again. To meet FSIS needs, we developed, validated, and implemented a new method of sample preparation and analysis to test cooked bacon for five NAs of most concern, which consist of <i>N</i>-nitroso-dimethylamine, -diethylamine, -dibutylamine, -piperidine, and -pyrrolidine. Sample preparation was based on the QuEChERS (quick, easy, cheap, effective, rugged, and safe) approach and analysis by gas chromatography–tandem mass spectrometry. Ruggedness was improved markedly in the analysis of the complex fatty extracts by backflushing the guard column, injection liner, and half of the analytical column after every injection. Validation results were acceptable with recoveries of 70–120% and <20% RSDs for the five NAs, with a reporting limit of 0.1 ng/g. NA concentrations in 48 samples were all <15 ng/g, with most <1 ng/g and many <0.1 ng/g. Also, microwave cooking of bacon gave slightly lower concentrations overall compared to pan-frying

Distribution and Excretion of Perfluorooctane Sulfonate (PFOS) in Beef Cattle (<i>Bos taurus</i>)

Perfluorooctane sulfonate (PFOS), a perfluoroalkyl surfactant used in many industrial products, is present in industrial wastes and in wastewater treatment plant biosolids. Biosolids are commonly applied to pastures and crops used for animal feed; consequently, PFOS may accumulate in the edible tissues of grazing animals or in animals exposed to contaminated feeds. There are no data on the absorption, distribution, and excretion of PFOS in beef cattle, so a 28-day study was conducted to determine these parameters for PFOS in three Lowline Angus steers given a single oral dose of PFOS at approximately 8 mg/kg body weight. PFOS concentrations were determined by liquid chromatography–tandem mass spectrometry in multiple tissue compartments. The major route of excretion was in the feces (11 ± 1.3% of the dose, mean ± standard deviation) with minimal PFOS elimination in urine (0.5 ± 0.07% of the dose). At day 28 the mean plasma concentration remained elevated at 52.6 ± 3.4 μg/mL, and it was estimated that 35.8 ± 4.3% of the dose was present in the plasma. Plasma half-lives could not be calculated due to multiple peaks caused by apparent redistributions from other tissues. These data indicate that after an acute exposure PFOS persists and accumulates in edible tissues. The largest PFOS body burdens were in the blood (∼36%), carcass remainder (5.7 ± 1.6%), and the muscle (4.3 ± 0.6%). It was concluded that PFOS would accumulate in edible tissues of beef, which could be a source of exposure for humans

Absorption and Excretion of ¹⁴C-Perfluorooctanoic Acid (PFOA) in Angus Cattle (Bos taurus)

Perfluoroalkyl substances (PFASs), such as perfluorooctanoic acid (PFOA), are environmentally persistent industrial chemicals often found in biosolids. Application of these biosolids to pastures raises concern about the accumulation of PFOA in the edible tissues of food animals. Because data on the absorption, distribution, metabolism, and excretion (ADME) of PFOA in cattle were unavailable, a study was conducted to determine pharmacokinetic parameters following a single oral exposure (1 mg/kg body weight of ¹⁴C-PFOA) in four Lowline Angus steers. Radiocarbon was quantified in blood, urine, and feces for 28 days and in tissues at the time of slaughter (28 days) by liquid scintillation counting (LSC) or by combustion analysis with LSC with confirmation by liquid chromatography–tandem mass spectrometry (LC-MS/MS). ¹⁴C-PFOA was completely absorbed and excreted (100.7 ± 3.3% recovery) in the urine within 9 days of dosing. The plasma elimination half-life was 19.2 ± 3.3 h. No ¹⁴C-PFOA-derived radioactivity was detected in edible tissues. Although PFOA was rapidly absorbed, it was also rapidly excreted by steers and did not persist in edible tissues, suggesting meat from cattle exposed to an acute dose of PFOA is unlikely to be a major source of exposure to humans

Perfluorooctane Sulfonate Plasma Half-Life Determination and Long-Term Tissue Distribution in Beef Cattle (Bos taurus)

Perfluorooctane sulfonate (PFOS) is used in consumer products as a surfactant and is found in industrial and consumer waste, which ends up in wastewater treatment plants (WWTPs). PFOS does not breakdown during WWTP processes and accumulates in the biosolids. Common practices include application of biosolids to pastures and croplands used for feed, and as a result, animals such as beef cattle are exposed to PFOS. To determine plasma and tissue depletion kinetics in cattle, 2 steers and 4 heifers were dosed with PFOS at 0.098 mg/kg body weight and 9.1 mg/kg, respectively. Plasma depletion half-lives for steers and heifers were 120 ± 4.1 and 106 ± 23.1 days, respectively. Specific tissue depletion half-lives ranged from 36 to 385 days for intraperitoneal fat, back fat, muscle, liver, bone, and kidney. These data indicate that PFOS in beef cattle has a sufficiently long depletion half-life to permit accumulation in edible tissues

Plasma and Skin Per- and Polyfluoroalkyl Substance (PFAS) Levels in Dairy Cattle with Lifetime Exposures to PFAS-Contaminated Drinking Water and Feed

Plasma and ear notch samples were removed from 164 Holstein cows and heifers, which had lifetime exposures to per- and polyfluoroalkyl substances (PFAS) through consumption of contaminated feed and water sources. A suite of nine PFAS including five perfluoroalkyl carboxylic acids (PFCA) and four perfluoroalkyl sulfonic acids (PFSA) was quantified in plasma and ear notch samples by liquid chromatography–mass spectrometry. Bioaccumulation of four- to nine-carbon PFCAs did not occur in plasma or skin, but PFSAs longer than four carbons accumulated in both plasma and skin. Exposure periods of at least 1 year were necessary for PFSAs to reach steady-state concentrations in plasma. Neither parity (P = 0.76) nor lactation status (P = 0.30) affected total PFSA concentrations in mature cow plasma. In contrast, lactation status greatly affected (P < 0.0001) total PFSA concentrations in ear notch samples. Skin samples could be used for biomonitoring purposes in instances when on-farm blood collection and plasma preparation are not practical

Blood-Based Ante-Mortem Method for Estimating PFOS in Beef from Contaminated Dairy Cattle

A blood-based screening method was developed to facilitate ante-mortem screening of dairy cattle suspected of containing elevated concentrations of perfluorooctanesulfonic acid (PFOS) in their muscle tissue. The collection and subsequent laboratory analyses of 28 paired blood plasma and muscle samples from PFOS-exposed dairy cattle provided the PFOS plasma and muscle data to develop a model to estimate muscle PFOS concentrations based on plasma PFOS concentrations. The blood-based ante-mortem screening approach could be applied to predict whether beef (skeletal bovine muscle) from suspect cattle populations (or subpopulations) exceeds a particular level of concern. The data analyses indicated that the relationship between muscle and plasma PFOS concentrations differed by the class of dairy cattle (heifer, lactating, and dry) and the duration of removal (withdrawal time) from exposure to PFOS. A plasma depletion model was also developed to evaluate the estimated withdrawal time required to reduce PFOS in dairy cattle muscle to below an identified level of concern. The model indicated complex PFOS plasma depletion dynamics with a nonconstant rate of depletion. The required withdrawal time also depends on the initial concentration distribution (which differed between heifers and lactating/dry cows) and the identified level of concern