it is the common view of medical and general science during the century-odd that we have discovered and been able to document radiation and its effects... that no amount is "generally recognized as safe" and standards need to be tightened.
In the end, you need evidence to back up such assertions not alleged consensus of vague groups of people.
Here you go. The story is discussing Tritium and here is some studies that you can go an examine yourself. I've copied the post for you to read.
These scientific studies are on the effects of tritium on living beings.
Some of them show that Triated water's effect is biologically mutagenic *because* it's a low energy emitter and it's characteristics makes readily absorbed by surrounding cells. The available evidence from studies conducted journal a list of effects. From those works;
Tritium can be inhaled, ingested, or absorbed through skin. Eating food containing 3H can be even more damaging than drinking 3H bound in water. Consequently, an estimated radiation dose based only on ingestion of tritiated water may underestimate the health effects if the person has also consumed food contaminated with tritium. (Komatsu)
Studies indicate that lower doses of tritium can cause more cell death (Dobson, 1976), mutations (Ito) and chromosome damage (Hori) per dose than higher tritium doses. Tritium can impart damage which is two or more times greater per dose than either x-rays or gamma rays.
(Straume) (Dobson, 1976) There is no evidence of a threshold for damage from 3H exposure; even the smallest amount of tritium can have negative health impacts. (Dobson, 1974) Organically bound tritium (tritium bound in animal or plant tissue) can stay in the body for 10 years or more.
It's often said "of all the elements in nuclear waste tritium is one of the more harmless ones" and while it's more benign than most other radioactive effluents it's toxicity should not be under-estimated.
Tritium can cause mutations, tumors and cell death. (Rytomaa) Tritiated water is associated with significantly decreased weight of brain and genital tract organs in mice (Torok) and can cause irreversible loss of female germ cells in both mice and monkeys even at low concentrations. (Dobson, 1979) (Laskey) Tritium from tritiated water can become incorporated into DNA, the molecular basis of heredity for living organisms. DNA is especially sensitive to radiation. (Hori) A cell's exposure to tritium bound in DNA can be even more toxic than its exposure to tritium in water. (Straume)(Carr)
First, as an isotope of hydrogen (the cell's most ubiquitous element), tritium can be incorporated into essentially all portions of the living machinery; and it is not innocuous -- deaths have occurred in industry from occupational overexposure. R. Lowry Dobson, MD, PhD. (1979)
Komatsu, K and Okumura, Y. Radiation Dose to Mouse Liver Cells from Ingestion of Tritiated Food or Water. Health Physics. 58. 5:625-629. 1990.
Dobson, RL. The Toxicity of Tritium. International Atomic Energy Agency symposium, Vienna: Biological Implications of Radionuclides Released from Nuclear Industries v. 1: 203. 1979.
Hori, TA and Nakai, S. Unusual Dose-Response of Chromosome Aberrations Induced in Human Lymphocytes by Very Low Dose Exposures to Tritium. Mutation Research. 50: 101-110. 1978.
Straume, T and Carsten, AL.Tritium Radiobiology and Relative Biological Effectiveness. Health Physics. 65 (6) :657-672; 1993. [This special issue of Health Physics is entirely devoted to Tritium]
Laskey, JW, et al. Some Effects of Lifetime Parental Exposure to Low Levels of Tritium on the F2 Generation. Radiation Research.56:171-179. 1973.
Rytomaa, T, et al. Radiotoxicity of Tritium-Labelled Molecules. International Atomic Energy Agency symposium,Vienna: Biological Implications of Radionuclides Released from Nuclear Industries v. 1: 339. 1979.