Xenophobia

I wonder how many xenobiotic substances there are in my body.

I suspect there are millions of different types of molecules. And then a few more types of metals, viruses, bacteria, molds and other simple organisms.

Every time I open my mouth to breath, drink or eat I am probably imbibing thousands of types of xenobiotic molecules.

In addition I have a few grams of titanium screws, the end of a graphite pencil, and 4 polymeric tooth filings.

Ignoring these, the total mass of environmentally- and food- absorbed xenobiotic substances in my body would probably be less than a gram, say 0.001% of total body mass.

A quick Google search tells me that the most toxic chemical is ricin (it is a protein but still a molecule as well) which is toxic to humans at 1 milligram.

Tetanus, a bacterium, can be fatal at 0.1 microgram.

Many other xenobiotic chemicals aren’t acutely toxic but do manage to kill us over time because they place an enormous load on the immune system, which is programmed to remove just about all unrecognised substances, just in case.

With our environment being full of xenobiotic substances that we can’t dodge, the result is that our immune systems are too busy removing these unknown (and probably mostly harmless) xenobiotic substances and therefore less able to fight off true invaders and the odd random and unwanted genetic expressions.