Linear no threshold (LNT)—the new homeopathy


The practice of homeopathy was founded by Samuel Hahnemann on two basic principles: (1) like cures like, and (2) therapeutic effects can be induced at infinitesimally low doses. So low are the doses recommended and used by practitioners of high dilution homeopathy that treatments are estimated to contain vanishingly few, if any, molecules, and far below the means of analytical detection even if present. The treatment dose results from a series of sequential dose dilutions (1:10, 1:100, 1:1000, and so on) yielding the controversial minimalist homeopathic dose 1.

Despite the high dilution of homeopathic preparations, treatments therewith are alleged to have therapeutic effects. Whether these alleged beneficial effects are due to the treatment or to the placebo effect is still fiercely debated.

The point of this editorial, however, is not to debate the issue of high dilution homeopathy, because it is a practice far outside the mainstream of medicinal science, therapy, and practice. More to the point, we emphasize that the cancer risk assessment practices of the U.S. Environmental Protection Agency (U.S. EPA), which are highly dependent on linear dose response modeling, ironically have a striking similarity to high dilution homeopathy.

The logical extension of the linearity at low dose modeling is that biological response is directly proportional to dose, regardless of how low that dose may be. The irony of similarity notwithstanding, the asserted biological responses at vanishingly low doses in homeopathy are dismissed with intellectual disdain by essentially the entire biomedical community, whereas the U.S. EPA and the Food and Drug Administration assert with great institutional and legal authority that even a single molecule of a chemical or one photon of ionizing radiation ultimately can cause cancer. In 1996, Goldman noted the absurdity thereof when he linearly calculated the increased risk of cancer, because of increased cosmic radiation, if the entire world population would add a 1-inch lift to their shoes 2.

This is the basic scientific and regulatory assumption even when people are actually exposed under normal conditions to doses several thousandfold or even several hundred-thousandfold lower than the tested animals 3—say, for example, through food. What is more, a dose of various carcinogens to humans associated with a de minimis risk of cancer (≤1 cancer/million/lifetime exposure) would commonly deliver many trillions of carcinogenic molecules each day for a 70-year lifespan, a value approaching and at times exceeding some 18 orders of magnitude greater than the so-called proverbial single molecule.

While homeopathy is the object of ridicule within the medical, biomedical, and public health communities for its low-dose predictions, the U.S. EPA routinely makes legally binding regulations based on a similar type of low-dose extremism.

Paracelsus' maxim that the dose makes the poison has been unduly radicalized by extrapolating it far beyond the empirical potential of science. Thereby, the linear no threshold (LNT) has become a dogma very similar to homeopathy. The latter, however, is being derided as nonscholarly, while the former is embraced with great scientific solemnity by the U.S. EPA. The same holds true, regrettably, for the European regulatory effort called REACH (Registration, Evaluation, Authorization, and Restriction of Chemicals), the largest ever investment into the safety of chemicals and consumer products 4. While the consumer can choose to accept high dilution homeopathic treatment, society as a whole is compelled to accept the regulatory environmental dictates of a globally accepted risk assessment process that lies far beyond the principles of reason, because it is both empirically unverifiable and inconsistent with a vast biomedical literature.