Does a Microgram of a Toxic Substance in Your Body Really Matter?

People are naturally skeptical about warnings that microscopic amounts of chemicals on the food we eat and on the dust we inhale could degrade our health and cause disease. It’s true that an occasional dose of a microscopic amount of a toxic chemical will probably not harm you; the real concern is about effects from years of exposure to multiple toxics. I hope to convince you that continual exposure to even submicroscopic amounts of toxics can be hazardous.

How much is a microgram? Almost nothing on a human scale. A one-eighth inch length of human hair weighs about 25 micrograms. One grain of sugar (as in the image) weighs about one microgram.  One red blood corpuscle weighs only 0.01 micrograms. Nevertheless, such small amounts can have detrimental effects on the body. The key to understanding this is the fact that there are a million billion molecules in one microgram!

To estimate how much toxic substance may be in our bodies consider this scenario. Assume that a person daily eats one half pound of food contaminated with five parts per million of a toxic, and that over 100 days 50% of the toxic is retained in the body. (For some substances it would be more.) This would result in 62 milligrams of toxic substance the body, corresponding to 2 million toxic molecules for each of the 100 trillion cells of the body. That is more than enough to damage some of the thirty thousand genes in the chromosomes of each cell! If only one day’s load of toxics were circulating in the blood, it would mean the presence of 1200 micrograms of toxic substance in the blood. To understand the significance of this figure, know that it would be comparable to the amount of thyroid hormones in the blood, and thousand of times larger than hormones of the pancreas, pituitary, and adrenal glands. Certainly not a prescription for health!

A conclusion drawn just from the numbers is that molecules of toxic chemicals in the body, especially when 100 or more types of toxic molecules are present, can greatly outnumber hormone molecules in the blood, and vastly outnumber DNA molecules of the genes in every cell of the body. Carcinogenic chemicals are those that are known to damage DNA, and damaged DNA often leads to cancer.

In the next post I will address the question of who is in charge of your health.


EPA’s fourth National Report on Human Exposure to Environmental Chemicals, 2010, gives average measured values of 75 to 100 micrograms of toxics in blood, and 10 to 25 micrograms of other toxics in the urine of human test subjects. More disturbing is the fact that 5% of the subjects had levels 5 to 10 times higher than these averages.


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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