• Health Physics Society

    The History of the Linear No-Threshold (LNT) Model Episode Guide
    The Health Physics Society (HPS) created this series of videos to examine the history of the most controversial question in our field: the LNT model.

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  • A Hormesis Revival and Its Reflective Champion Ed Calabrese

    A Hormesis Revival and Its Reflective Champion Ed Calabrese More

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  • The Paradox of Finding Motivation Through Fear

    UMass Amherst research informs a New York Times article. Read more.

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  • Finding a New ‘Sweet Spot’ for Improving Cancer Risk Assessment

    UMass Amherst environmental toxicologist, with others, proposes to optimize public health. Read more.

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  • A Nuclear Paradigm Shift? U.S. regulators may radically revise safety assumptions about atomic radiation.
  • Linear No-Threshold Model and Standards for Protection Against Radiation; Notice of Docketing and Request for Comment
  • Nuclear Regulatory Commission request public comments on changing the basis for its “Standards for Protection Against Radiation” from the Linear No-Threshold (LNT) model to the Radiation Hormesis model.
  • Lauding Low Doses-A Revolutionary Field Called Hormesis Shows that Dangerous Substances can be Beneficial at Low Levels

    Microbiology and Molecular Genetics, University of Texas Medical School in Houston
    October 1, 2009, Ransome van der Hoeven
    “Hormesis and aging in C. elegans”

    University of Kansas Medical Center
    October 2, 2009, Karl Rozman, Ph.D
    “Hormesis or the Effects of Low Doses of Toxic Agents”

    Metagenics International Congress of Nutritional Medicine 2009
    Jun 6-8, 2009, Dr Jeffrey Bland PhD

    Dr Jeffrey Bland’s 30 year career in nutritional biochemistry has spanned roles as a research professor, thought leader and internationally recognised expert in human nutrition. More than 60,000 Health Professionals have attended Dr Bland’s seminars and educational programs during the last 20 years. He is regarded worldwide as the principal educator in nutritional and functional medicine. Dr Bland will present the latest research in the following areas:

    Nutrigenomics and tissue specific inflammation.

    Hormones and hormesis – Who’s pulling the strings?

    Hormesis and epigenetics in clinical practice.

    Bloomsburg University, Department of Mathematics, Computer Science and Statistics
    November 18, 2009, Jason Elsinger
    Use of Double Quadratic Polynomials for Nonlinear Dose-Response Modeling in Biological Experiments

    The study of dose-response modeling, and in particular, the favorable biological responses to low exposures to chemicals known as hormesis, can be used to determine the best dose level for maximal benefit. The study of hormesis has become very popular over the past decade. Gaylor (2004) used a single quadratic to model the hormesis curve. Here, we argue that using a double quadratic (one for the down trend and one for the up trend), will result in a better description of the process. The maximum likelihood method is used to estimate model parameters. In order to solve the nonlinear likelihood equations, the EM (Expectation-Maximazation) algorithm is utilized to convert the nonlinearity to a linear problem. We then use an example with real data to illustrate our methodology.

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  • Best Seller by Clive Cussler brings HORMESIS to public attention

    Quote from: Medusa: A novel from the NUMA files by Clive Cussler with Paul Kemprecos, G.P. Putnam’s Sons, Penguin Group (USA) Inc. (2009), pp 236-237.

    “An antiviral has to kill the pathogens without hurting the host. The medusa toxin went beyond that, actually protecting its host organism’s health…for a while, anyway. The process is called hormesis. In small doses, a toxin can trigger repair mechanisms in the body, maybe even retard aging. It works in the same way exercise does, by stressing the body so that it changes the metabolism for the better.”

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  • New publication, Hormesis and Medicine, in the British Journal of Clinical Pharmacology
  • Hormesis Deserves the Respect and Attention of Toxicologists

    News Release

    Hormesis Deserves the Respect and Attention of Toxicologists

    A comprehensive review published in Environmental Toxicology and Chemistry argues that toxicologists can positively affect public health and reduce the economic costs of drug treatment by increasing their knowledge of hormesis and applying its principles to their discipline.

    Hormesis is an adaptive reparative process that organisms and biological systems undergo when exposed to stress, toxicity, or disruptions in homeostasis. During toxicity testing, the health of organisms actually improved when they were exposed to low levels of some chemicals. Hormesis has not been taken seriously, mainly because of its historical link to homeopathy. Furthermore, hormesis research is demanding in terms of resources and time.

    However, this review answers many questions about hormesis and contends that it is worthy of scientific research rather than disinterest, and that its use is applicable to many disciplines including toxicology, pharmacology, and risk assessment.

    The U.S. Environmental Protection Agency’s interest in cancer endpoints has also led to the reemergence of hormesis in the mainstream scientific community. The observation of hormesis in disease incidence and tumor formation (toxicological endpoints) and pain and seizure modulation (pharmacological endpoints) is also driving increased attention.

    Data on hormesis from toxicological studies can lead to improved risk assessment protocols and practices that serve the scientific community and translate into public health and economic benefits.

    The review is “Hormesis: Why It Is Important to Toxicology and Toxicologists” Edward J. Calabrese. The article appears in Environmental Toxicology and Chemistry, Volume 27, Issue 7, 2008, published by Allen Press.

    Full text of the article is available at


    About Environmental Toxicology and Chemistry

    Environmental Toxicology and Chemistry is a publication of the Society of Environmental Toxicology and Chemistry. It is interdisciplinary in scope and integrates the fields of environmental toxicology; environmental, analytical, and molecular chemistry; ecology; physiology; biochemistry; microbiology; genetics; genomics; environmental engineering; chemical, environmental, and biological modeling; epidemiology; and earth sciences. Emphasis is given to papers that enhance capabilities for the prediction, measurement, and assessment of the fate and effects of chemicals in the environment. To learn more about the Society, please visit:

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  • Biological Stress Response Terminology: Integrating the concepts of adaptive response and preconditioning stress within a hormetic dose-response framework
  • Threshold—dose—response model—RIP: 1911 to 2006
  • Noise, stress and annoyance
  • Nutritional Hormesis

    By DP Hayes
    New York City Department of Health and Mental Hygiene, New York, NY USA
    European Journal of Clinical Nutrition (2006), 1-13

    Objective: Hormesis, the biological and toxicological concept that small quantities have opposite effects from large quantities, is reviewed with emphasis on its relevance to nutrition.

    Results: Hormetic and other dose-response relationships are categorized, depicted, and discussed. Evidence for nutritional hormesis is presented for essential vitamin and mineral nutrients, dietary restriction, alcohol (ethanol), natural dietary and some synthetic pesticides, some herbicides, and acrylamide. Some of the different hormetic mechanisms that have been proposed are reviewed.

    Conclusions: The credence and relevance of hormesis to nutrition are considered to be established. The roles of hormesis in nutritional research and in formulating nutritional guidelines are discussed

    Sponsorship: The New York City Department of Health and Mental Hygiene.
    European Journal of Clinical Nutrition advance online publication, 2 August 2006; doi:10.1038/sj.ejcn.1602507

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  • Hormesis: Is it an important factor in herbicide use and allelopathy?
  • Hormesis gets massive support: The new theory could overturn scores of environmental regulations

    Hormesis gets massive support
    The new theory could overturn scores of environmental regulations
    By Rebecca Renner
    Science News—October 4, 2006

    Humble yeast cells may be shedding new light on the controversial theory of hormesis. Cancer researchers collected data on 13 strains of yeast, generating a large database of their responses to different chemicals. For low doses, those reactions are best explained by hormesis—a nonintuitive dose–response theory—and not by theories currently used in risk assessment, according to a new analysis by University of Massachusetts toxicologist Edward Calabrese and colleagues, published in Toxicological Sciences online on September 1.

    Hormesis (160KB PDF) explains that low doses can have the opposite effect of high doses, such that chemicals that can have harmful biological effects in relatively large amounts can have beneficial effects in small quantities. Calabrese and colleagues have found in scores of recent papers signs that such behavior may be ubiquitous. But risk assessments and environmental regulations throughout the world operate on one of two assumptions: either doses below a toxicological threshold have no adverse effects, or all doses have similar effects.
    This means that hormesis has the potential to overturn some environmental regulations, and its relevance to such policies has engendered lively debate. “The proper understanding and utilization of hormesis will do a much better job of both protecting and promoting public health than the policy-based defaults that are currently in use,” Ralph Cook, a physician with RRC Consulting, and Calabrese wrote this summer. Not so, argued Kristina Thayer, a toxicologist with the National Institute of Environmental Health Sciences, and colleagues last year. “If hormesis were used in the decision-making process to allow higher exposures to toxic and carcinogenic agents, this would substantially increase health risks for many, if not most, segments of the general population,” they wrote.

    The new analysis is the first to use a single large database to put hormesis to the test against the threshold model, says Calabrese. “In this single, detailed data set, we again find that the threshold model fails to predict the low-dose responses and the hormesis model does,” he says. Read the entire article…

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  • Neurohormetic phytochemicals: low–dose toxins that induce adaptive neuronal stress responses
  • Hormesis Outperforms Threshold Model in National Cancer Institute Antitumor Drug Screening Database


    Summary of Findings
    The supplementary data (Tables S1-S4, Figures S1-S3) represent the same analyses
    using a BMD(2.5) that were presented with a BMD(10) in the body of the paper. The
    supplemental data using the BMD(2.5) are incompatible with threshold model predictions, in
    agreement with the findings using the BMD(10), but even more so. The findings with the
    BMD(2.5) are also highly consistent with the predictions of the hormetic model for all
    methodologies employed to estimate below threshold responses. Using the BMD(2.5)
    instead of BMD(10) had two principal effects. First, use of BMD(2.5) reduced the estimated
    BMDs compared to the BMD(10). As a result, the number of chemical and strain
    combinations with estimated BMDs < 3.7 uM for which we could not assess the behavior of the responses below the BMD increased from 7,558 out of 28,457 [for BMD(10)] to 12,167 out of 28,457. Second, for the chemical and strain combinations for which we could assess the behavior of the responses below the BMD, the evidence supporting the hormetic hypothesis is notably stronger using the BMD(2.5) method than the BMD(10) method, regardless of the analytical approach employed. ToxSciHormesisYeast

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  • Hormesis in Carcinogenicity of Non-genotoxic Carcinogens
  • The Interphone Study Group report on cell phone safety: Missing the answer by adhering to a flawed principle

    As most people know, the safety of cell phones has been a hot topic of debate since several published reports suggested a possible increase in ipsilateral (same-side) brain tumours (malignant gliomas and benign meningiomas) among heavy users.

    Although health authorities cautioned that the data from these studies were insufficient to provide a definitive answer, concerned governments from Ontario to India were quick to give advice: children, whose brains might be especially vulnerable to the effects of radiofrequency (RF) emissions, should be discouraged from using cell phones except in an emergency.

    Unfortunately, with today’s publication of the highly-awaited Interphone Study Group report, those hoping for that “definitive” answer are certain to be confused. But should they?

    This largest-to-date study, conducted between 2000 and 2004, involved 13 countries, including Canada. Carried out under the auspices of the World Health Organization’s International Association for Research on Cancer (IARC), it involved 2708 glioma patients, 2409 meningioma patients, and 2972 carefully matched healthy controls.

    The subjects, all between the ages of 30 and 59, were interviewed in person to determine the frequency and cumulative call time (total hours) of cell phone use (or non-use) over several time spans: 1 – 1.9 years; 2 -4 years; 5 – 9 years; 10 or more years.

    The findings? As compared to “never-users”, there was an overall 20 to 30% decreased risk of glioma and meningioma tumours in those who used cell phones for 1 -9 years; even after 10 or more years of use, a 2% decreased risk of glioma and a 17% decreased risk of meningioma was found.

    When cumulative call time was compared among ever- and never-users, once again a 20 to 30% decreased risk of tumours was observed among users who accumulated less than 1640 hours over 1 to 10 years.

    However, once cumulative call times went above 1640 hours for 10 or more years of use (approximately 30 minutes daily), a 15% increase in meningiomas and a 40% increase in gliomas was observed. Perhaps tellingly, the rate of gliomas was a whopping 377% higher in those who accumulated more than 1640 hours over just 1 – 4 years (i.e., ranging from 1.1 – 4.5 hours of daily use). Moreover, as suggested in the earlier studies, their location favored the ipsilateral temporal lobe (the part of the brain closest to the ear).

    Yet, despite the study’s findings (both “good” and “bad”), the committee of authors was extremely reluctant to draw any conclusion at all, stating that “[methodological] biases and error prevent a causal interpretation…”. As a result, they called for yet further investigation on “the possible effects of long-term heavy use of mobile phones”, especially among adolescents and teenagers.

    The reason is this: they were concerned that an excess of brain tumours was seen only at the highest level of use, with no evidence of a linear increase up to that point. Indeed, except at the highest level of use, there appeared to be a protective effect of cell phones against brain tumours, something the authors dismissed as “implausible”….so implausible that, despite other studies showing a similar trend, the Interphone Study Group is “currently exploring the possibility of correcting the [risk] estimates mathematically”. And with that statement, if any bias exists, it appears to be more in the thinking of the investigators than as a result of the design of the study.

    Why? For decades, health officials, toxicologists and regulators, including those associated with the IARC, have only recognized the validity of what is called a “linear (straight line) dose-response” effect. But, based on hundreds upon hundreds of published examples of chemical, hormonal and physical agents, whose dose responses are “hormetic” (derived from the word, hormone, meaning differing effects at low and high levels of exposure), many prominent scientists, chief among them, U. of Massachusetts professor, Dr. Edward Calabrese, believe that the hormetic model, rather than the linear model, may more accurately represent the biological effect, especially at lower levels of exposure, of many agents on human health.

    One example is the “J-shaped” curve that applies to alcohol; as compared to non-drinkers, decreased cardiovascular-related mortality is observed in populations that consume up to 2 ounces per day; exceeding that amount results in higher mortality (including cancer) that increases the more one drinks.

    Furthermore, although there is evidence of benefit when plants and animals are exposed to low-level terrestrial and extra-terrestrial radiation, the IARC disregards studies of low-dose radiation effects, believing instead that there is no safe lower threshold of human exposure to radiation. That thinking likely extends to RF emissions from cell phones.

    So what is the truth about cell phones and the risk of brain tumours? I believe that the answer lies in the hormetic model proposed by Dr. Calabrese and his colleagues. A “J-shaped” dose response (decreased risk of brain tumours with low to moderate use; increased risk with excessive use) is highly consistent with the findings of the Interphone Study Group. Sadly, the “linear thinkers” will say otherwise. Officially, nothing will have been resolved and stiff-necked adherence to a seriously flawed risk model will have obscured highly pertinent findings.

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  • First Conference on Hormesis

    Radiation Hormesis Conference (CA), April 1985 [PDF]

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  • First Conference on Hormesis

    Conference on Radiation Hormesis
    Oakland California
    August 14 – 16, 1985
    Program and Abstracts [PDF]

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