Jeffery A. Foran

Risk-based consumption advice for farmed Atlantic and wild Pacific salmon contaminated with dioxins and dioxin-like compounds

We reported recently that several organic contaminants occurred at elevated concentrations in farmed Atlantic salmon compared with concentrations of the same contaminants in wild Pacific salmon [Hites et al. Science 303:226–229 (2004)]. We also found that polychlorinated biphenyls (PCBs), toxaphene, dieldrin, dioxins, and polybrominated diphenyl ethers occurred at higher concentrations in European farm-raised salmon than in farmed salmon from North and South America. Health risks (based on a quantitative cancer risk assessment) associated with consumption of farmed salmon contaminated with PCBs, toxaphene, and dieldrin were higher than risks associated with exposure to the same contaminants in wild salmon. Here we present information on cancer and noncancer health risks of exposure to dioxins in farmed and wild salmon. The analysis is based on a tolerable intake level for dioxin-like compounds established by the World Health Organization and on risk estimates for human exposure to dioxins developed by the U.S. Environmental Protection Agency. Consumption of farmed salmon at relatively low frequencies results in elevated exposure to dioxins and dioxin-like compounds with commensurate elevation in estimates of health risk.

A survey of metals in tissues of farmed Atlantic and wild Pacific salmon

Contamination of fish tissues with organic and inorganic contaminants has been a pervasive environmental and public health problem. The present study reports the concentrations of nine metals in tissues of farmed Atlantic salmon (Salmo salar) and two species of wild-caught salmon (chum [Oncorhynchus keta] and coho [O. kisutch]) analyzed as part of a global survey of contaminants in these fish. Of the nine metals, organic arsenic was significantly higher in farmed than in wild salmon, whereas cobalt, copper, and cadmium were significantly higher in wild salmon. None of the contaminants exceeded federal standards or guidance levels.

Principles for the selection of doses in chronic rodent bioassays

Dose selection in chronic rodent bioassays has been one of the most debated issues in risk assessment. The Committee on Risk Assessment Methods of the National Research Council attempted, but failed, in 1993 to reach consensus on how to select doses for chronic rodent bioassays. However, a more recent effort conducted by the ILSI Risk Science Institute has resulted in a consensus set of principles for dose selection, including selection of the highest dose for chronic rodent bioassays. The principles encourage a move away from sole reliance on a maximum tolerated dose (MTD), as it has been traditionally defined (primarily by body weight and histopathology), and toward the use of sound scientific and toxicologic principles for the selection of all doses in the chronic bioassay. Specifically, the principles recommend that dose selection for chronic studies must be based on sound toxicologic principles; dose selection should consider human exposure; dose selection should be based on a variety of endpoints and effects derived from prechronic studies; and dose selection should consider physicochemical and other factors. Implementation of the principles internationally will have two important benefits; improvement in the quality and consistency of the rodent bioassay and international harmonization of dose selection procedures.

Environmental medicine: its introduction into a medical school primary care requirement

Summary. One hundred and twelve medical students participating in a required 6‐week primary‐care rotation completed a pretest of environmental medicine knowledge and attitudes at the start of the rotation and a similar posttest on the last day of the rotation. Control group students were to participate in the usual weekly didactic sessions of the clerkship. Intervention students were given a booklet describing environmental considerations in clinical medicine and introducing them to the concept of risk assessment, three computer‐assisted instruction cases, and a problem‐based learning (PBL) exercise involving role‐play. Because voluntary compliance with evaluation forms was poor during year one, during the second year students in the intervention group were required to return evaluation forms in order to sit for the course final examination. Knowledge and attitudes of both intervention and control groups were compared at baseline and at the end of the rotation. Students in the intervention group also completed process evaluations of the intervention materials. Students in both intervention and control groups increased knowledge gains significantly during the second year of the intervention, while neither group improved during year 1. This may have been due to a ‘spill‐over’ effect among primary‐care teachers implementing the intervention. Students ranked both environmental and occupational medicine of least importance in their training compared with eight other aspects of medicine, and this ranking did not improve with intervention. The PBL exercise was well received by the students. Of 28 evaluations, 27 ranked the session in the highest 3 of a 5‐part Likert scale for worthwhile content, and 24 would recommend the session to a friend. When asked to list the most important things learned, 23 mentioned learning to look for additional information, and 12 mentioned realizing that the doctor does not know everything (and should admit that).

Regulatory implications of hormesis

This discussion of the regulatory implications of hormesis focuses on technical and social issues that will determine whether hormesis can be incorporated in the development and implementation of risk-based regulations. Particular attention is given to the development of qualitative and quantitative regulatory limits (e.g., standards or criteria) for water pollutants, hazardous wastes, and pesticides. Hormesis is described, and is used in this article, as a dose response relationship that is stimulatory at low doses, but inhibitory at higher doses, and as the zone of a dose/response curve, from the no observed effect level (NOEL) to tenfold below the NOEL, where a bene®cial effect exists relative to the background effect. Standards and criteria, as well as qualitative limits on the allowable quantities of potentially toxic chemicals in the environment are typically risk-based and conservatively de®ne the amounts of these substances that can occur in the environment without appreciable risk to ecosystems and human health. They are derived by consideration of chemical hazard or toxicity, potency as described by chemical-speci®c dose/response (d/r) curves, human or environmental exposure to chemicals, and uncertainty, all in the context of quantitative risk assessment. For non-carcinogens, a reference dose (RfD) or an allowable daily intake (ADI) are typically used as the basis for numeric criteria or standards derived from toxicologic information and quantitative risk assessment methods (for a description of RfD derivation). Hormesis has not, to date, been a component of the risk-based approach to the development of standards and criteria for environmental pollutants. There are at least two signi®cant road blocks to incorporating hormesis in risk-based regulations. The numerous scienti®c and technical questions that need to be addressed will keep a variety of research programs active for many years. Even if these research programs are successful in answering the array of technical questions, strong social objections may be raised and may ultimately prevent the use of hormesis in risk-based regulatory decision making, despite overwhelming scienti®c support. Both the scienti®c questions and the social road blocks are discussed in this article.

Assessing the Risks Associated With Exposure to Waterborne Pathogens: An Expert Panel's Report on Risk Assessment†

The resurgence of outbreaks of waterborne diseases in the United States underscores the need for quantitative methods for assessing the human health risks associated with various types of waterborne pathogens in diverse environments (e.g., drinking water, waste water, recreational water) under different exposure scenarios (e.g., ingestion, inhalation from aerosols). An expert panel developed a three-stage general framework for conducting risk assessments of waterborne pathogens. An initial problem formulation stage involving all stakeholders identifies the purpose of the risk assessment, the critical issues to be addressed, and how the results might be used to protect public health. The analysis characterizes both the exposure and the health effects. This compilation of quantitative and qualitative data, expert opinion, and other information yields a host/pathogen profile that explicitly identifies the assumptions and uncertainties associated with the profile. The final stage, risk characterization, states the likelihood and types and magnitude of effects likely to be observed in the exposed population under the expected exposure scenario, including all the inherent assumptions and uncertainties. This characterization will be used by risk managers and policy makers to reduce human health risks and by risk communication specialists to inform the public.