The dose makes the poison.

Paracelsus was a 16th century Swiss German physician, alchemist, astrologer who found the discipline of toxicology. He came up with this basic principle of toxicology: The dose makes the poison.

“All things are poisons, for there is nothing without poisonous qualities. It is only the dose which makes a thing poison.”

So many of us misunderstand basic chemistry and what ‘toxic’ really means. I can relate. Chemistry was my WORST subject in high school. Most of what I have learned (and since become interested in) has been cultivated through my PhD studies and in projects since then.

Toxicity is an indicator of how poisonous a substance is to a biological entity. Any chemical can be toxic if absorbed or consumed in large enough amounts. Chemistry is all around us and we are all comprised of chemicals (matter). Some chemicals are man made others occur naturally: in our bodies, manufactured in plants, in our food and in the air we breathe.  In fact, there are more naturally occurring chemicals than man-made ones.  Chemical reactions and interactions in our bodies occur all the time.

Joni Kamiya-Rose posted this status update the other day on Facebook which, in turn, inspired my blog post for today.

joni rose toxic

To Joni’s last point… YES, wouldn’t that be great! I can’t imagine anyone who wouldn’t want safer options.

To (further) clear up misunderstandings and provide some context on toxicity, I crafted this table.  In toxicology, the median lethal dose, LD50 (see column 3) is the dose required to kill half the members of a tested population after a specified testing time. The test was developed by J.W. Trevan in 1927. In the table , I outline a variety of familiar (some less familiar) materials and their toxicity levels.  Please note: the LD50 levels outlined in the table below are based on oral ingestions by rats.  Toxicity rankings are based on the EPA’s categorization (I through IV) (Title 40 of the Code of Federal Regulations).

toxicity table


35 thoughts on “The dose makes the poison.

  1. I’m a home brewer of beer. I read quite a few blogs and such where others worry about chemicals (or worse….GMOoooooooooooos) in beer. Either they say, “I don’t put” or “I don’t want” “chemicals in my beer.” All the time forgetting the most dangerous chemical in the beer is the alcohol (ethanol).

    For a great visual on caffeine, I recommend CGP Grey’s YouTube video. It’s less than four minutes and it’s informative and entertaining.

  2. Very interesting. Of course, LD50 is only one way to measure toxicity, and it fails to account for a number of different ways that substances could have negative health effects, especially over the long-term.
    We also need to consider the level and risk of exposure. Sure, copper sulfate is more toxic, based on LD50, than glyphosate. But let’s look at what the EPA says about copper:
    “It is one of the micronutrients essential to human health…Generally, current
    available data and literature studies indicate that there is a greater risk from the deficiency of copper intake than from excess intake.” (
    I didn’t bother to look up glyphosate, but somehow I doubt “RoundUp-deficiency” is a nutritional concern!

    • Thanks Rob for commenting. I always appreciate your insights. Yes, LD50 is only one part of the story…

      Sorry for brevity of reply…am in the middle of seminar.ttyl, c

    • First, copper sulfate and copper are not the same. Copper’s LD50 is 5,000 mg/kg, while copper sulfate’s LD50 is 300 mg/kg.

      Second, this post is but one look at toxicity, not a full dissertation on every aspect of toxicity, which would require a few semesters in college to go over. That doesn’t mean the information is irrelevant. The point is the claims that organic growing is somehow “toxicity free” or “chemical free” are disingenuous and inaccurate.

      • Thanks, Chuck. I’m not sure why you assumed I didn’t know the difference between copper sulfate and copper. If you refer to the link I provided, you’ll see that the EPA references copper because it is the active component of concern in various copper-containing pesticides, including copper sulfate.
        Secondly, I never suggested that the information in this post was irrelevant – I simply pointed out that it was part of a larger picture, which, as you say, is very complex.
        Finally, my experience is that most reliable, reasoned descriptions of organic agriculture avoid implying that organic products are “free” of anything.I do not think it is fair to judge anything based on statements made by those at the extremes.

    • copper sulfate is generally considered non toxic to humans taken within recommended dosage
      however it is the toxicity to aquatic life that is a major issue , because of this lack of human danger and because it easily gets washed off, organic farmers have no issue spraying their crops multiple times
      the runoff ends up in the water, streams, creeks rivers and lakes

      • Organic farmers are required to document other management strategies employed before resorting to an approved pesticide, and they are required to test to ensure that copper levels are not accumulating to excessive levels in the soil. Of course, if you have any citations to back your accusations, I’d welcome the opportunity to address them.

      • Luca, thanks for posting your comment. As an organic producer, Rob is – of course – very knowledgeable. I defer to his expert opinion on this. Thank you, both, for engaging on this blog post.

  3. The dose makes the poison is very near the top of my list of scientific truisms I wish everyone would understand intuitively. That simple fact reduces a lot of unnecessary fear and would save people a ton of money from hucksters.

  4. It’s worth noting that the EPA rescinded the registration of rotenone as pesticide in 2006 for all uses except as piscicide (to control invasive fish, primarily by agencies like the USFS).

    For various reasons it remained available in over-the-counter pesticides until at least 2011. Perhaps it is still used agriculturally in other countries, but it can’t be legally used in the US in agriculture, organic or otherwise.

    • Thanks for the comment and the link, Kevin. The LD50 that I have listed on the table is for oral doses in rats. Worth noting, according to your reference here, that it is the ACCUMULATION of NAPQI that results in a toxicity problem and “not acetaminophen itself nor any of the major metabolites.” NAPQI is the toxic by-product produced DURING metabolism of acetaminophen.

      Thanks again, Kevin. Appreciate your input on this.

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