Sara J. Lupton

Brominated flame retardants such as polybrominated diphenyl ethers (PBDEs) can contaminate food which results in consumer exposure. In 2018-19, 54 beef livers and 14 dairy cow livers were collected for PBDE analysis along with paired fat samples (previously published) to assess comparisons of congener profiles between liver and fat, concentration levels in liver, and consumer exposure. The mean ΣPBDE concentration in all the livers was 54.03 pg g^-1 wet weight (ww) and the median was 35.45 pg g^-1 ww with concentrations ranging from 4.92 to 426.67 pg g^-1 ww. The congeners with the highest contributions based on the mean were BDE47 (48%), BDE99 (21%), and BDE153 (17%). The ΣPBDE concentrations of the livers when compared to the paired fat samples were not significantly correlated and the congener contribution for BDE99 was lower in the liver compared to the paired fat samples while BDE153 was higher. An average U.S. consumer daily intake of PBDEs in beef liver was estimated to be 0.024 ng kg bw^-1day^-1.

For the past three decades, the U.S. Department of Agriculture (USDA) has conducted surveys of the domestic meat supply every 5 years to determine the temporal trends and current levels of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and non-ortho-polychlorinated biphenyls (no-PCBs), referred to as dioxins. In the 2023-2024 dioxin survey, fat samples from beef (n = 145) and pork (n = 143) along with Siluriform muscle (n = 53) were collected from U.S. slaughter facilities and analysed for 17 PCDD/Fs and 3 no-PCBs. Toxic equivalency factors (TEFs) from 2005 were utilised to calculate the sum-toxic equivalency (sum-TEQ) for all samples for comparison to previous surveys. The sum-TEQs ranged from non-detect (nd) to 2.75 pg TEQ/g lipid for the current survey. Beef, pork, and Siluriform median sum-TEQs (nd = ½ LOD) were 0.150, 0.032, and 0.076 pg TEQ/g lipid or wet weight for Siluriformes, respectively. Declining trends in median concentrations are observed for the surveys over the last 30 years. Statistical analysis of this survey compared to the previous survey, shows significant decreases (p < 0.001) in the median concentrations for the sum-TEQs of PCDD/F and no-PCB for all classes. These temporal declines provide evidence that measures for minimisation of PCDD/F and no-PCB release in meat products have been working.

Human exposure to polybrominated diphenyl ethers (PBDEs), a class of brominated flame retardants, can occur through consumption of contaminated foods. Since 2007, U.S. meat and poultry samples (beef, pork, chicken, turkey) have been collected every 5 years to assess PBDE levels and consumer exposure to seven PBDEs. Mean ∑PBDE concentrations from beef, pork, chickens, turkeys, dairy cows, and siluriformes (catfish) were 0.19, 0.48, 0.11, 0.60, 0.28 ng/g lipid weight (lw), and 2.5 ng/g wet weight (ww). The ΣPBDEs for all meat classes ranged from 0.005 to 17.7 ng/g lw. Comparison of the 2018-19 survey to the 2007-08 and 2012-13 surveys revealed an overall decrease in the median ΣPBDE residue for all four meat classes with significant reductions in the medians, at 40 - 45%, for pork, chicken, and turkey. As in the previous surveys, BDEs 47 and 99 had higher percentage contributions to the ΣPBDE concentrations than other PBDE congeners, which indicated the penta-BDE formulation was a likely exposure source for animals. An estimate of U.S. consumer daily intake of PBDEs from meat and poultry was 5.0 ng/day which is a decrease from the 2012-13 survey of 6.4 ng/day.

Plasma, milk and tissue samples were collected from 30 dairy cattle (0.4 to 8.9 years of age) with lifetime exposures to perfluoroalkyl substances (PFAS) removed from a PFAS-contaminated farm and provided PFAS-free feed and water. Twenty cattle were slaughtered 2 weeks after removal from the farm and tissues were collected for histological and residue analyses. Milk and/or plasma were collected from all remaining cattle at 2-week intervals and milk samples were collected daily but were analyzed at the same intervals as plasma samples. The remaining cattle were slaughtered 20 and 22 weeks after the initial set of 20 animals were slaughtered. While many incidental and normal background findings were noted on histological evaluation, no consistent histological finding was associated with PFAS exposure. Perfluoroalkyl carboxylic acids (PFCA) and perfluoro butane sulfonic acid (PFBS) were not generally detected in milk, plasma and tissues, but perfluoroalkyl sulfonic acids (PFSA) were quantifiable throughout the 22-week withdrawal period in most matrices. Estimated plasma half-lives of perfluorohexane sulfonic acid (PFHxS), perfluoroheptane sulfonic acid (PFHpS), linear perfluorooctane sulfonic acid (L-PFOS), perfluoro-3-methyl heptanesulfonate (3Me-PFOS) and perfluoro-6-methyl heptanesulfonate (6Me-PFOS) ranged from 4 to 10 weeks, but the estimates were associated with large confidence intervals. Across animal status (heifer, lactating, dry), natural log transformed (Ln) plasma residues of PFHxS and L-PFOS were generally well correlated with Ln-transformed PFHxS and L-PFOS residues in lung, muscle, liver and kidney (R², 0.7572 to 0.9394) whereas the strongest relationships of Ln-transformed L-PFOS residues among tissues were between lung and liver, kidney and muscle (R², 0.8287 to 0.9138).

Daily dietary exposure estimates from beef, pork, chicken, turkey and siluriform fish were calculated using toxic equivalency (TEQ) data from the U.S. Department of Agriculture's survey of dioxins and dioxin-like compounds (DLCs) in the domestic meat supply and consumption data. Exposure estimates for the whole population and age groups were based on mean consumption of a commodity and mean or 90th percentile TEQ dioxin levels from the survey. Ratios of the exposure estimates to the U.S. EPA oral reference dose (RfD) of 0.7 pg TEQ/kg bw/day were calculated to determine if domestic meat might contribute materially to consumer exposure. In general, normal consumption of lean beef, pork, chicken and turkey will not cause exposures exceeding the RfD. Non-lean meats will have higher dioxin levels as dioxins accumulate in fat, therefore consumption of non-lean meat might cause higher exposure than compared to lean meat. However, on a mean basis, none of the exposure estimates for non-lean beef, pork, chicken or turkey exceeded the RfD for any of the age groups. For some age groups, especially toddlers, there are commodities such as non-lean beef in the 90th percentile of dioxin TEQs and siluriform fish that might exceed the RfD on occasion.

The U.S. Department of Agriculture (USDA) conducted a survey of domestic animal products including beef fat, pork fat, chicken fat, turkey fat, dairy cow fat, and siluriform fish muscle (i.e. catfish) to determine the current residue levels of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and non-ortho-polychlorinated biphenyls (no-PCBs). The following types of fat samples were analysed: beef from heifers and steers (referred to as “beef”), pork, chicken, turkey, dairy cow (referred to as “dairy cow”), and siluriform fish muscle, which includes catfish. The survey is conducted every 5 years. Fat samples for each slaughter class and siluriform fillets were collected from U.S. federally inspected slaughter facilities, processed, and analysed for 17 PCDD/Fs and 3 no-PCBs. Toxic equivalency concentrations were calculated using 2005 toxic equivalency factors and summed (sum-TEQ) for all slaughter classes. The sum-TEQs ranged from non-detect (nd) to 16.5 pg TEQ/g lipid. The median sum-TEQs, when nd = ½ LOD, for beef, pork, chicken, turkey, dairy cow, and siluriform fish were 0.48, 0.08, 0.07, 0.21, 0.38, and 0.62 pg TEQ/g lipid (wet weight for siluriform fish), respectively. A comparison of the current and previous surveys typically depicts a significant declining trend depending on the slaughter class (such as chicken and turkey), however, beef and pork fat median values slightly increased and decreased, respectively, but neither were significant compared to the previous survey. The congener patterns for some high concentration beef and pork fat samples suggested that pentachlorophenol treated wood continues to be a likely on-farm dioxin exposure source.

Perfluorooctanoic acid (PFOA), used as a surfactant in consumer and industrial products, is frequently found in biosolids from wastewater treatment plants. When present in biosolids applied to croplands, PFOA has potential to contaminate feed and fodder used by livestock, but the extent of PFOA transfer from soil to plants is not well characterized. A single dose of [ 14 C]-PFOA was applied to unplanted soil or soil containing growing alfalfa. PFOA transport through unplanted soil and uptake by alfalfa was monitored over a 10-week study period. Radiocarbon was initially measured in roots, stems, and leaves 7 days after PFOA application to soil. PFOA accumulation was greatest in leaves during the 10-week sampling. By week 10, PFOA migration through unplanted soil had reached a depth of 22.8 ± 2.5 cm. In contrast, PFOA migrated to 7.5 ± 2.5 cm in soil containing alfalfa plants. The greatest predictor of PFOA concentration in alfalfa leaves was PFOA concentration in the top 5 cm of soil; PFOA concentrations at lower depths were not correlated with alfalfa PFOA levels. PFOA transport through soil may be slowed by the presence of forage, however PFOA accumulation in edible portions of forage plants may increase food animal exposure to PFOA residues.

Perfluorooctanoic acid (PFOA) is a perfluorinated alkyl substance (PFAS) used as surfactant in a wide variety of industrial and consumer products. Over the past decade, concern has increased over the presence of PFOA in biosolids from wastewater treatment plants used as fertilizer on agricultural lands having the potential to enter the food chain. In this study, the uptake of 14C-PFOA from soil by alfalfa was determined, as was the bioavailability of 14C-PFOA-incurred into alfalfa in Sprague-Dawley rats. Alfalfa leaves accumulated PFOA to as high as 4-5 µg/g of dry leaf, approximately 10 times higher than accumulation in the stem. Alfalfa was ground for feeding to 15 female Sprague-Dawley rats (175-200 g). Animals within metabolism cages were fed 10 g of feed (6 g alfalfa + 4 g ground rat chow) twice a day for 14 days (equivalent to 50 ug-PFOA/kg/day). At the end of the feeding period, rats (n=3) were sacrificed at withdrawal days of 0, 3, 7, 11, and 14 days. During the feeding and withdrawal phases, urine and feces were collected daily. At sacrifice, blood, liver, kidney, adipose, muscle, skin, brain, heart, adrenals, spleen, lungs, and thymus were removed and assayed for 14C-PFOA by combustion and LSC analysis. Rats eliminated 72.8 ± 3.4% of the total dose via urine at 14-days, but urinary radioactivity fell below the LOD by day 3 of the withdrawal period. Fecal elimination was 6.5 ± 1.2 % of the dose and fell below the LOD by 2 days of withdrawal. The rapid and high elimination via urine indicates that a majority of the dose was absorbed. The uptake of PFOA into alfalfa was low from a high organic content soil, however, PFOA was highly bioavailable from the alfalfa when used as a feed component for rats. This study provides data for regulators investigating PFOA bioavailability and disposition in animals or animal products exposed to contaminated feed.

Polybrominated diphenyl ethers (PBDEs) levels in environmental matrices have generally declined following their phaseout as flame retardants. The objective of this study was to determine the absorp...