Safe Dose Revisited

In December I posted an article on “Safe Dose,” and I think it is worthwhile to look deeper into this guiding principle of toxicology.

It has long been assumed that there exists some small dose of a toxic substance, such that less than that amount will produce no harmful effect. It is worth examining this important issue. Why? Because the national standards for safety of toxic chemical are based upon the principle, and producers and users of toxic chemicals are allowed to sell or use the chemicals as long as people exposed to the chemical are unlikely to exceed the “safe dose.” You may wonder if this is a realistic approach to hazards of toxic chemicals, or if it is an escape clause for polluters.

Is “safe dose” a valid concept? It is a valid concept for those chemicals that are readily detoxified by the body and eliminated in the urine. As long as these rates are greater than the rate of ingestion of the toxic chemical, there will be no accumulation and it will be harmlessly eliminated from the body before tissues are damaged. This analysis is correct if the foreign chemical is not ferociously damaging. The concept of safe dose may also gain validity because cells can repair some kinds of damage, so that at sufficiently low doses of some chemicals, repair may exceed initial damage. Safe dose is not a valid concept when irreparable damage is done or when the level of the substance in tissues continues to increase. For example, it is accepted there is no threshold (i.e., safe lower dose) for radiation (e.g., from X-rays), because every tiny bit of radiation disrupts DNA and therefore produces mutations which can lead to cancerous cells. The other situation where safe dose is not valid is where the chemical accumulates in the body. In such cases of continuous or frequent exposure to the chemical, what begins as a very small level in the body becomes increasingly larger, until a point is reached at which damage is certain to occur. This is the case with toxic metals, such and mercury.

On a non technical level, the issue is, do you want ANY toxic chemicals in your body? Surely the answer is a loud “No!” A pregnant woman does not want any amount of a hormone disrupter or a nervous system toxicant to be in her blood and the blood of her fetus. She wants to be free of any toxics. She certainly is not likely to feel safe with a hundred or more toxics circulating in her body, as test data shows to be the case in many mothers.

In a National Geographic magazine article (October 2006), “The Pollution Within,” David Duncan describes how 165 foreign chemicals were found in his body. Would you feel safe if you had 100 to 200 foreign chemicals in your body, as long as each was present at a “safe dose”?


About donlouis

The author has long had a keen interest in staying healthy and fit, and in doing whatever I can to keep the natural environment unpolluted and a healthy space for people and all animals. As a former Board Member of a municipal water district, I regularly had to deal with the issue of water quality. I first became aware of radiation hazards from toxic materials while working on uranium for nuclear reactors. During the 1960s I was tuned into the global hazard from Strontium 90 raining down from atmospheric testing of nuclear bombs. While working in the chemical industry in later years I became aware of the many forms of chemical contaminants entering the environment every day, and resolved to do something about it. I am able to make sense out of the voluminous descriptions of common toxic chemical because of my training in chemistry, with a Ph.D. degree and several decades of research and development work in the chemical industry. My training and experience enables me to present to readers reliable and current information on the topic of chemical hazards in the environment, and their threats to human health. All my life I have loved hiking and camping in nature. Skiing, river kayaking, and tennis have been my favorite physical activities. Nature photography is my artistic passion.
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