Toxins and Carcinogens
There is a lot of fear around toxins and carcinogens these days. A lot of this is bullshit. Some points worth noting:
- Almost anything is harmful at a certain dose. Water will kill at a high enough dose by disturbing the osmotic balance.
- Everything is harmless at a certain dose. Claims such as "lead is harmful at any dose" are claims about statistics that are not literally true. The probability that lead does damage seems to be proportional to dose, which means that at very small doses the probability is very small, which is what we call "harmless" in everyday language.
- Assuming that "synthetic" chemicals are harmful and "natural" chemicals are harmless is fallacious. The most harmful chemical known (botulinum toxin), with a median lethal dose (LD50) of a couple hundred nanograms is a natural product produced by soil bacteria. Many synthetic compounds (e.g. food additives) are harmless.
- Many substances are carcinogenic in high doses which often does not imply that the chemical is carcinogenic in clinically relevant low doses. For instance, many compounds naturally found in plants are "carcinogenic" by this standard.
- Alcohol and tobacco both cause significant exposure to carcinogens that is far more relevant than, say, exposure to pesticides.
- Something being in use for a long time does not mean it is harmless. Harmful lead salts have been used in paint and cosmetics for millenia.
- Want to find out if something is harmful? Look for actual scientific studies, preferably in vivo and in humans. Don't just look for one study that confirms your expectations, read the abstracts of several and see what the total picture is.