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Background: Only recently has the environment been clearly implicated in the risk of antibiotic resistance to clinical outcome, but to date there have been few documented approaches to formally assess these risks.Objective: We examined possible approaches and sought to identify research needs to enable human health risk assessments (HHRA) that focus on the role of the environment in the failure of antibiotic treatment caused by antibiotic-resistant pathogens.Methods: The authors participated in a workshop held 4–8 March 2012 in Québec, Canada, to define the scope and objectives of an environmental assessment of antibiotic-resistance risks to human health. We focused on key elements of environmental-resistance-development “hot spots,” exposure assessment (unrelated to food), and dose response to characterize risks that may improve antibiotic-resistance management options.Discussion: Various novel aspects to traditional risk assessments were identified to enable an assessment of environmental antibiotic resistance. These include a) accounting for an added selective pressure on the environmental resistome that, over time, allows for development of antibiotic-resistant bacteria (ARB); b) identifying and describing rates of horizontal gene transfer (HGT) in the relevant environmental “hot spot” compartments; and c) modifying traditional dose–response approaches to address doses of ARB for various health outcomes and pathways.Conclusions: We propose that environmental aspects of antibiotic-resistance development be included in the processes of any HHRA addressing ARB. Because of limited available data, a multicriteria decision analysis approach would be a useful way to undertake an HHRA of environmental antibiotic resistance that informs risk managers.Citation: Ashbolt NJ, Amézquita A, Backhaus T, Borriello P, Brandt KK, Collignon P, Coors A, Finley R, Gaze WH, Heberer T, Lawrence JR, Larsson DG, McEwen SA, Ryan JJ, Schönfeld J, Silley P, Snape JR, Van den Eede C, Topp E. 2013. Human health risk assessment (HHRA) for environmental development and transfer of antibiotic resistance. Environ Health Perspect 121:993–1001; http://dx.doi.org/10.1289/ehp.1206316

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Pharmaceuticals and personal care products (PPCPs) have recently been detected in the aquatic environment. Many studies have identified domestic waste water discharge as the source for detectable concentrations of PPCPs in surface water. PPCPs are a concern for the aquatic environment when production and use are sufficiently large and physicochemical properties are appropriate. Hydrophilic PPCPs present in surface water or waste water may also affect ground water quality where water is used to recharge ground water. However, less is known about how efficiently PPCPs are removed during percolation through the subsurface. The scope of this study was to examine the fate of selected PPCPs during ground water recharge at two water reuse sites where secondary and tertiary treated waste water is used for subsequent ground water recharge. The ground water recharge sites selected differ in aboveground treatment and geohydrological settings. The selected pharmaceutials represent blood lipid regulators, analgesics/anti‐inflammatories, blood viscosity agents, and antiepileptics. Organic iodine was used as a surrogate parameter for X‐ray contrast agents. Composite samples of treated waste water and from ground water monitoring wells were collected and analyzed for Pharmaceuticals using gas chromatography with mass spectroscopic detection. The study revealed that the stimulant caffeine, analgesic/anti‐inflammatory drugs such as diclofenac, ibuprofen, ketoprofen, naproxen, and fenoprofen, and blood lipid regulators such as gemfibrozil were efficiently removed to concentrations near or below the detection limit of the analytical method after retention times of less than six months during ground water recharge. The antiepileptics carbamazepine and primidone were not removed during ground water recharge under either anoxic saturated or aerobic unsaturated flow conditions during travel times of up to eight years. Organic iodine showed a partial removal only under anoxic, saturated conditions as compared to aerobic conditions and persisted in the recharged ground water.