Toxicology — the principles.

Toxicology is the study of adverse effects of chemicals (including metals and heavy metals) on living organisms. Sometimes the body responds instantly, yet at other times there is a delayed response; in fact some of the carcinogenic toxins may not seem to show for some tens of years. Also, exposure to low doses of substances may continue for years, and so the cumulative effect becomes a relevant factor. When multiple toxicants are involved, there is the well-recognised ’synergistic’ effect, whereby A+B =AB, where AB has much more of an effect than either A or B.

Some toxic effects are reversible, and this depends on whether injured tissues or organs are able to regenerate. For instance, the liver has a high ability to regenerate, and so toxic injury is more likely to be reversible. On the other hand, the central nervous system (the specialised cells of which cannot divide and be replaced), is much more vulnerable to toxic exposure and the effects of toxicity to brain and nerve tissue is generally considered to be irreversible.

But how do we take toxins and poisons into our bodies in the first place?

Generally speaking, we absorb them through our gastro-intestinal tract, after ingestion, or we absorb them through the lungs (as gases or vapours), or via the skin. In addition, any toxicant which is able to pass through the placental barrier is able to enter the bloodstream of the unborn child directly. The resultant plasma levels of toxins tend to be the same in both mother and unborn baby, although the foetal tissue has the ability to concentrate the toxins to varying degrees in its various organs.

We come into contact with poisons all the time, so why aren’t we in a constant state of overwhelm, and how do we survive this continuous onslaught? Just as we can take toxins into the body, nature has equipped us with excretory systems. The primary organ of excretion is the kidney, although in addition to excretion in the urine, toxins are removed from the body via the faecal route, and the lungs also expel noxious gases. In fact, any discharge from the body can expel toxins, and this includes sweat, tears, saliva and breast-milk! Nursing mums beware!

Which organ systems can be involved? The simple answer is any! And so, if any system can be involved, the symptoms can be wide-ranging. Because the body is a complete system, the under-functioning of any of its parts can have a deleterious effect. Let’s take an example: the very fact that the kidney is considered to be a major excretory organ is, in part, by virtue of the fact that it receives about 25% of the cardiac output. The kidney constantly filters the blood – day in, day out. The delivery rate of toxins to this small organ is huge. During the manufacture of urine, part of the role of the kidney is to concentrate it, which means that the relative levels of toxin, being prepared by the kidney for excretion, is relatively high. This makes the kidney more susceptible to injury, and the less well it functions, the worse the scenario. The less the kidney excretes the more toxic the body becomes, and the more the burden on the system as a whole. By now the blood is more toxic, and so increased levels of poisons are delivered to all areas. This then causes other organs to malfunction, and we have the start any number of diseases. And this is with reference to the kidney. Throw in all the other organs and tissues, and we have the potential for severe pathology at some stage.

For further reference click here; Metals and chemicals, and Mercury.