Ryan S. Prosser

Human health risk assessment of pharmaceuticals and personal care products in plant tissue due to biosolids and manure amendments, and wastewater irrigation

Amending soil with biosolids or livestock manure provides essential nutrients in agriculture. Irrigation with wastewater allows for agriculture in regions where water resources are limited. However, biosolids, manure and wastewater have all been shown to contain pharmaceuticals and personal care products (PPCPs). Studies have shown that PPCPs can accumulate in the tissues of plants but the risk that accumulated residues may pose to humans via consumption of edible portions is not well documented. This study reviewed the literature for studies that reported residues of PPCPs in the edible tissue of plants grown in biosolids- or manure-amended soils or irrigated with wastewater. These residues were used to determine the estimated daily intake of PPCPs for an adult and toddler. Estimated daily intake values were compared to acceptable daily intakes to determine whether PPCPs in plant tissue pose a hazard to human health. For all three amendment practices, the majority of reported residues resulted in hazard quotients <0.1. Amendment with biosolids or manure resulted in hazard quotients ≥0.1 for carbamazepine, diphenhydramine, salbutamol, triclosan, and sulfamethazine. Irrigation with wastewater resulted in hazard quotients of ≥0.1 for ambrettolid, carbamazepine, diclofenac, flunixin, lamotrigine, metoprolol, naproxen, sildenafil and tonalide. [corrected]. Many of the residues that resulted in hazard quotients ≥0.1 were due to exposing plants to concentrations of PPCPs that would not be considered relevant based on concentrations reported in biosolids and manure or unrealistic methods of exposure, which lead to artificially elevated plant residues. Our assessment indicates that the majority of individual PPCPs in the edible tissue of plants due to biosolids or manure amendment or wastewater irrigation represent a de minimis risk to human health. Assuming additivity, the mixture of PPCPs could potentially present a hazard. Further work needs to be done to assess the risk of the mixture of PPCPs that may be present in edible tissue of plants grown under these three amendment practices.

Bioaccumulation of triclosan and triclocarban in plants grown in soils amended with municipal dewatered biosolids.

Biosolids generally contain the microbiocidal agents triclosan (TCS) and triclocarban (TCC) that are persistent during wastewater treatment and sorp to organic material. The present study investigated the concentration of TCS in tissues of radish, carrot, and soybean grown in potted soil amended with biosolids. Highest mean concentrations of TCS in radish, carrot, and soybean root tissue midway through the life cycle were 24.8 ng/g, 49.8 ng/g, and 48.1 ng/g dry weight, respectively; by the conclusion of the test, however, concentrations had declined to 2.1 ng/g, 5.5 ng/g, and 8.4 ng/g dry weight, respectively. Highest mean concentrations of TCS in radish and carrot shoot tissue were 33.7 and 18.3 ng/g dry weight at days 19 and 45, respectively, but had declined to 13.7 ng/g and 5.5 ng/g dry weight at days 34 and 69, respectively. Concentration of TCS in all samples of soybean seeds was below method detection limit (i.e., 2.8 ng/g dry wt). The present study also examined the concentration of TCS and TCC in edible portions of green pepper, carrot, cucumber, tomato, radish, and lettuce plants grown in a field amended with biosolids. Triclosan was detected only in cucumber and radish up to 5.2 ng/g dry weight. Triclocarban was detected in carrot, green pepper, tomato, and cucumber up to 5.7 ng/g dry weight. On the basis of the present study and other studies, we estimate that vegetable consumption represents less than 0.5% of the acceptable daily intake of TCS and TCC. These results demonstrate that, if best management practices for land application of biosolids in Ontario are followed, the concentration of TCS and TCC in edible portions of plants represents a negligible exposure pathway to humans.

Modeling Uptake of Selected Pharmaceuticals and Personal Care Products into Food Crops from Biosolids-Amended Soil

Biosolids contain a variety of pharmaceuticals and personal care products (PPCPs). Studies have observed the uptake of PPCPs into plants grown in biosolids-amended soils. This study examined the ability of Dynamic Plant Uptake (DPU) model and Biosolids-amended Soil Level IV (BASL4) model to predict the concentration of eight PPCPs in the tissue of plants grown in biosolids-amended soil under a number of exposure scenarios. Concentrations in edible tissue predicted by the models were compared to concentrations reported in the literature by calculating estimated human daily intake values for both sets of data and comparing them to an acceptable daily intake value. The equilibrium partitioning (EqP) portion of BASL4 overpredicted the concentrations of triclosan, triclocarban, and miconazole in root and shoot tissue by two to three orders of magnitude, while the dynamic carrot root (DCR) portion overpredicted by a single order of magnitude. DPU predicted concentrations of triclosan, triclocarban, miconazole, carbamazepine, and diphenhydramine in plant tissues that were within an order of magnitude of concentrations reported in the literature. The study also found that more empirical data are needed on the uptake of cimetidine, fluoxetine, and gemfibrozil, and other ionizable PPCPs, to confirm the utility of both models. All hazard quotient values calculated from literature data were below 1, with 95.7% of hazard quotient values being below 0.1, indicating that consumption of the chosen PPCPs in plant tissue poses de minimus risk to human health.

Sensitivity of a green alga to atrazine is not enhanced by previous acute exposure

Exposure to atrazine in small lotic systems can be episodic, with short-term pulses (peaks) followed by lower, decreasing concentrations. Algae and macrophytes recover rapidly from pulsed exposure to atrazine, but reported observations of population response to subsequent exposures are minimal and inconclusive. Consequently, the sensitivity of Pseudokirchneriella subcapitata to atrazine following a pulsed exposure was assessed. Exposure concentrations reflected amplifications of those observed in streams from highly vulnerable watersheds in regions of intense use. Initial pulsed atrazine exposure at 0, 150 or 300 μg/L for 24-h was followed by 72-h exposure to 0, 5, 10, 25, or 50 μg/L. Measured responses were cell density, growth rate, chlorophyll-a, and maximum quantum yield of photosystem II. Algal recovery was rapid and prior pulsed exposure to atrazine did not significantly affect subsequent sensitivity (EC10s, EC25s) for any endpoint, indicating no changes in tolerance at the population level for this species.

Toxicity of biosolids‐derived triclosan and triclocarban to six crop species

Biosolids are an important source of nutrients and organic matter, which are necessary for the productive cultivation of crop plants. Biosolids have been found to contain the personal care products triclosan and triclocarban at high concentrations relative to other pharmaceuticals and personal care products. The present study investigates whether exposure of 6 plant species (radish, carrot, soybean, lettuce, spring wheat, and corn) to triclosan or triclocarban derived from biosolids has an adverse effect on seed emergence and/or plant growth parameters. Plants were grown in soil amended with biosolids at a realistic agronomic rate. Biosolids were spiked with triclosan or triclocarban to produce increasing environmentally relevant exposures. The concentration of triclosan and triclocarban in biosolids-amended soil declined by up to 97% and 57%, respectively, over the course of the experiments. Amendment with biosolids had a positive effect on the majority of growth parameters in radish, carrot, soybean, lettuce, and wheat plants. No consistent triclosan- or triclocarban-dependent trends in seed emergence and plant growth parameters were observed in 5 of 6 plant species. A significant negative trend in shoot mass was observed for lettuce plants exposed to increasing concentrations of triclocarban (p<0.001). If best management practices are followed for biosolids amendment, triclosan and triclocarban pose a negligible risk to seed emergence and growth of crop plants.

Assessing the bioaccumulation potential of ionizable organic compounds: Current knowledge and research priorities

The objective of the present study was to review the current knowledge regarding the bioaccumulation potential of ionizable organic compounds (IOCs), with a focus on the availability of empirical data for fish. Aspects of the bioaccumulation potential of IOCs in fish that can be characterized relatively well include the pH dependence of gill uptake and elimination, uptake in the gut, and sorption to phospholipids (membrane-water partitioning). Key challenges include the lack of empirical data for biotransformation and binding in plasma. Fish possess a diverse array of proteins that may transport IOCs across cell membranes. Except in a few cases, however, the significance of this transport for uptake and accumulation of environmental contaminants is unknown. Two case studies are presented. The first describes modeled effects of pH and biotransformation on the bioconcentration of organic acids and bases, while the second employs an updated model to investigate factors responsible for accumulation of perfluorinated alkyl acids. The perfluorinated alkyl acid case study is notable insofar as it illustrates the likely importance of membrane transporters in the kidney and highlights the potential value of read-across approaches. Recognizing the current need to perform bioaccumulation hazard assessments and ecological and exposure risk assessment for IOCs, the authors provide a tiered strategy that progresses (as needed) from conservative assumptions (models and associated data) to more sophisticated models requiring chemical-specific information. Environ Toxicol Chem 2017;36:882-897.

Bioaccumulation of perfluorinated carboxylates and sulfonates and polychlorinated biphenyls in laboratory-cultured Hexagenia spp., Lumbriculus variegatus and Pimephales promelas from field-collected sediments

Polychlorinated biphenyls (PCBs) and perfluorinated carboxylates and sulfonates (PFASs) are persistent pollutants in sediment that can potentially bioaccumulate in aquatic organisms. The current study investigates variation in the accumulation of PCBs and PFASs in laboratory-cultured Hexagenia spp., Lumbriculus variegatus and Pimephales promelas from contaminated field-collected sediment using 28-day tests. BSAF(lipid) (lipid-normalized biota-sediment accumulation factor) values for total concentration of PCBs were greater in Hexagenia spp. relative to L. variegatus and P. promelas. The distribution of congeners contributing to the total concentration of PCBs in tissue varied among the three species. Trichlorobiphenyl congeners composed the greatest proportion of the total concentration of PCBs in L. variegatus while tetra- and pentabiphenyl congeners dominated in Hexagenia spp. and P. promelas. Perfluorooctane sulfonate (PFOS) was present in all three species at concentrations greater than all other PFASs analyzed. Hexagenia spp. also produced the greatest BSAF(lipid) and BSAF(ww) (non-lipid-normalized biota-sediment accumulation factor) values for PFOS relative to the other two species. However, this was not the case for all PFASs. The trend of BSAF values and number of carbon atoms in the perfluoroalkyl chain of perfluorinated carboxylates varied among the three species but was similar for perfluorinated sulfonates. Differences in the dominant pathways of exposure (e.g., water, sediment ingestion) likely explain a large proportion of the variation in accumulation observed across the three species.

Aquatic hazard assessment of MON 0818, a commercial mixture of alkylamine ethoxylates commonly used in glyphosate‐containing herbicide formulations. Part 2: Roles of sediment, temperature, and capacity for recovery following a pulsed exposure

A series of toxicity tests with MON 0818, a commercial surfactant mixture of polyoxyethylene tallow amines, were performed: 1) in the presence of sediment for benthic invertebrates and fish: 2) to examine the recovery capacity of Daphnia magna and 4 primary producers after a pulsed (24-h) exposure; and 3) to examine the potential effect of increased water temperature on toxicity of MON 0818 to 2 cold-water fishes. In the presence of sediment, no acute (24-h) mortality was observed for 3 of the 5 species up to 10 mg L-1 . The median effective concentrations for the other 2 species were significantly greater than for water only tests. The EC50 at 15 °C for Salvelinus alpinus was statistically lower than that at 10 °C. Latent effects of a 24-h exposure (1 mg L-1 ) were observed for Rhabdocelis subcapitata and Chlorella vulgaris, as indicated by delayed growth during recovery phase; however, both cultures were able to recover, as indicated by a lack of changes in maximum absolute growth rates. No significant effects of a 24-h exposure to MON 0818 were observed for Oophila sp. (1.5 mg L-1 ) or Lemna minor (100 mg L-1 ). Latent mortality after a 24-h exposure to 5 mg L-1 was observed during the recovery phase for D. magna; however, reproduction endpoints on surviving individuals were not altered. The results indicate that quick dissipation of MON 0818 in the presence of sediment can reduce the effects on exposed organisms, and that full recovery from 24-h exposures to concentrations of MON 0818 equal to, or greater than, those expected in the environment is possible. Environ Toxicol Chem 2017;36:512-521.

Toxicity of Cúspide 480SL® spray mixture formulation of glyphosate to aquatic organisms

In 2011, an alternative formulation of glyphosate (Cúspide 480SL®) was chosen to replace Roundup-SL®, Fuete-SL®, and Gly-41® for the control of Erythroxylum coca, the source of cocaine, in Colombia. Cúspide 480SL contains the active ingredient glyphosate isopropylamine (IPA) salt, which is the same active ingredient used in previous formulations. However, Cúspide 480SL contains an alkyl polyglycoside surfactant rather than the polyethoxylated tallow amine (POEA) surfactant used in other formulations and known to be more toxic to nonprimary producing aquatic organisms than glyphosate itself. An adjuvant, Cosmo-Flux F411, and water also are added to the spray mixture before application. Aquatic ecosystems adjacent to the target coca fields might be exposed to the spray mix, placing aquatic organisms at risk. Because no toxicity data were available for spray mixture on aquatic organisms, acute toxicity tests were conducted on aquatic plants, invertebrates, and fish, by using the Cúspide 480SL spray mix as described on the label. Based on the median effective concentration (EC50) values for similar organisms, the spray mixture was less toxic to aquatic organisms than formulations previously used for the control of coca (i.e., Roundup-SL, Fuete-SL, and Gly-41). A physical effect induced by Cosmo-Flux F411 was observed in Daphnia magna, Ceriodaphnia dubia, and Hyalella azteca, causing the invertebrates to be trapped in an oily film that was present at the surface of the water. However, a hazard assessment for the Cúspide 480SL spray mix, using estimated worst-case exposure scenario concentrations and EC50 values from the toxicity tests, indicated de minimis hazard for the tested aquatic animals, with hazard quotients all <<1.

Aquatic hazard assessment of MON 0818, a commercial mixture of alkylamine ethoxylates commonly used in glyphosate‐containing herbicide formulations. Part 1: Species sensitivity distribution from laboratory acute exposures

The sensitivity of 15 aquatic species, including primary producers, benthic invertebrates, cladocerans, mollusks, and fish, to MON 0818, a commercial surfactant mixture of polyoxyethylene tallow amines, was evaluated in standard acute (48-96-h) laboratory tests. In addition, the potential for chronic toxicity (8 d) was evaluated with Ceriodaphnia dubia. Exposure concentrations were confirmed. No significant effects on any endpoint were observed in the chronic test. A tier-1 hazard assessment was conducted by comparing species sensitivity distributions based on the generated data, as well as literature data, with 4 exposure scenarios. This assessment showed moderate levels of hazard (43.1% of the species exposed at or above median effective concentration levels), for a chosen worst-case scenario-unintentional direct over-spray of a 15-cm-deep body of water with the maximum label application rate for the studied formulations (Roundup Original, Vision Forestry Herbicide; 12 L formulation ha-1 , equivalent to 4.27 kg acid equivalent [a.e.] ha-1 ). The hazard decreased to impairment of 20.9% of species under the maximum application rate for more typical uses (6 L formulation ha-1 , 2.14 kg a.e. ha-1 ), and down to 6.9% for a more frequently employed application rate (2.5 L formulation ha-1 , 0.89 kg a.e. ha-1 ). Finally, the percentage (3.8%) was less than the hazardous concentration for 5% of the species based on concentrations of MON 0818 calculated from maximum measured concentrations of glyphosate in the environment. Environ Toxicol Chem 2017;36:501-511.