>A common error, when judging the effects of radioactivity or the toxicity of some substance, is
to assume a linear response model without threshold (that is, without a dose rate below which there
is no ill effect). Presumably there is no threshold effect for cumulative poisons like heavy metal
ions (mercury, lead), which are eliminated only very slowly if at all. But for virtually every organic
substance (such as saccharin or cyclamates), the existence of a finite metabolic rate means that
there must exist a finite threshold dose rate, below which the substance is decomposed, eliminated,
or chemically altered so rapidly that it has no ill effects. If this were not true, the human race
could never have survived to the present time, in view of all the things we have been eating.
>Indeed, every mouthful of food you and I have ever taken contained many billions of kinds
of complex molecules whose structure and physiological effects have never been determined—and
many millions of which would be toxic or fatal in large doses. We cannot doubt that we are daily
ingesting thousands of substances that are far more dangerous than saccharin—but in amounts
that are safe, because they are far below the various thresholds of toxicity. But at present there is
hardly any substance except some common drugs, for which we actually know the threshold.
The most dangerous substances fall into a few categories. Things like insecticides (which is what this thread is about) are designed to kill animals. Insects, but still, their physiology is close enough to humans. And things like heavy metals and radioactive substances. Which our ancestors weren't really exposed to.
For non cancer risks like carbon monoxide poisoning thresholds are generally extremely important and relatively straightforward.
The problem is people are designed to get cancer, or alternatively we are very good at pushing cancer off long enough not to be important but no longer than that. So, the odds of cancer by 90 are very high, and simply shifting a few years early may take a relatively tiny change.
In other words models about cancer risks based on 18 year olds don't extrapolate well to 60 year olds.
An alternative explanation is that we have a lot of "backup capacity" such that small amounts of damage are not noticed by reasonable tests (or potentially are impossible to measure) until we reach a point where we fail to function. I have enough beta cells in my pancreas that you can destroy a lot of them and you will not see my blood sugar lose control; maybe it takes slightly longer to steady, but unless you have previous tests of how well I function I might still look "normal", but if you destroy enough then eventually I stop being able to regulate blood sugar and I clearly have diabetes.
Maybe if you kept tons of test results of when I was normal, you could try to compare, but in addition to the problem that most people don't take tests when they don't notice issues (and even when they do, the medical profession just seems to love to destroy files after a number of years: it just feels criminal to destroy data like that on someone's medical history), the test subject is also getting older and you expect them to not function as well :/.
Even if you know something is failing, often medical science just doesn't care: over a decade ago I was getting hearing tests done occasionally as I could tell I was losing the hearing in my right year, but I had hearing that was so good (better than most people even for being in my early 20s, when everyone still has good hearing... and so usually aren't taking hearing tests) that the doctors would explain I'd topped out their charts, had "excellent hearing", and they couldn't even know if something was wrong. Well: I definitely have extremely worse hearing in my right ear now :/.
It wouldn't surprise me if the exact opposite were true: that medical science often estimates things assuming there are "thresholds", when quite possibly almost nothing is subject to a threshold effect while often being cumulative; the issue being just that the response curve is sufficiently sloped, and is further skewed by tests based on results instead of on internal state, that it looks like there are thresholds, and so we underestimate essentially everything dangerous.
An alternative explanation is that we have a lot of "backup capacity" such that small amounts of damage are not noticed by reasonable tests (or potentially are impossible to measure) until we reach a point where we fail to function.
We are actually all supposed to be 7 feet tall and full of muscles, we just don't know it because every last one of us has been stunted by poor diet and what not.
I generally agree with your points about thresholds, and the fact that some synthetics don't degrade very quickly.
But this is funny:
> And things like heavy metals and radioactive substances. Which our ancestors weren't really exposed to.
Please excuse the Wikipedia quote. The numbers are right, and it's written well enough:
> 40K occurs in natural potassium (and thus in some commercial salt substitutes) in sufficient quantity that large bags of those substitutes can be used as a radioactive source for classroom demonstrations. In healthy animals and people, 40K represents the largest source of radioactivity, greater even than 14C. In a human body of 70 kg mass, about 4,400 nuclei of 40K decay per second.[2]
In some cases a large enough difference in quantity is a difference in quality. The doses of radiation that are dangerous to humans, are orders of magnitude larger than what you get from eating a banana. The amount of bananas you'd need to consume to get radiation poisoning is unimaginable.
Which is the basis for the fact (often disbelieved) that you're exposing yourself to radiation when you sleep next to someone. And that sometimes leads to the what if question 'How many people would have to spoon to create a critical mass?'
For all (most?) cancers, you need many mutations in one cell.
There is some probability that a mutation will trigger an internal check in the cell to detect bad mutations, and the cell will commit suicide.
There is also some probability that the cell will die accidentally before the second mutation.
There is some probability that the immune system will detect something fishy and kill the cell just in case.
If the time between each mutation is bigger, then you have more time to get lucky and remove the cell while it has a single mutation, before it can accumulate more mutations and become dangerous.
So a lower dose will increase the time between mutations and make the case of two accumulative bad mutations less common. Then at small doses, the effect is not linear and perhaps below some threshold the ability of the body to detect problems will fix all the cases before you notice.
The problem is that it's very difficult to measure the effect of very low doses for a long time. (You have to test the drug in some animal that lives for a long time like elephants instead of mice.) (And it's difficult to get funding and graduate students for a 20 year experiment.)
So the "linear non threshold model" is slightly pessimistic, it err on the side of caution, but it's probably good enough and not too alarmist.
--
Technical note: There are actually no cells with zero mutations. All cells have some mutations. Some have less, some have more. Some mutations are dangerous, most are innocuous, a few may be advantageous. But to simplify the discussion, I just ignored this and imagine that usually the cells have no mutations.
It depends highly on the mechanism of carcinogenesis. Lead is a (possible) carcinogen, and accumulates even in relatively small quantities because it takes up residence in your bones and is slowly released back into your blood over years. Others may be eliminated rapidly and only cause damage in large or continuous doses. Frustratingly the answer is often "it depends". The very low end of the spectrum of exposures is often the most relevant to humans (due to our relatively low exposure to most things), but very hard to study, because the effects are often drowned out by other causes of morbidity/mortality.
In a side note, Organophosphates replaced Organochlorides for a very similar reason. They have a much faster elimination rate, reducing the time that they stay in the food chain (and hopefully reducing the exposure of non-target species). Organochlorines, on the other hand, were very stable, which made them easily stored, but also caused biomagnification, where animals further up the food chain started concentrating it in their bodies as they ate smaller animals that had been exposed. This caused serious environmental effects, leading to the shift to the pesticides we use today.
It's all about luck, you know? They'll all cause some sort of cellular damage. Cancer is when you get super unlucky and it's the right sort of cellular damage that leads to unchecked growth and disables apoptosis.
Well, your hypothesis is definitely scientific, since it can be disproven. Couple of counter-hypotheses:
- Consuming less food requires the body to use fat-reserves. Some of these might have been storing heavy metals. With a quick enough change in diet, these might pose a significant risk.
- Consuming less food might alter your gut microbiology. Disheveling this balance might create the risk of infection or even worse.
- Consuming less food (to be precise, less lipids), might alter, or even disable certain parts of the metabolism, often leading to deficiencies in supplies for the immune system, thus making us more vulnerable to 'poisons'.
I don't know which of the above hypotheses are correct, but I am sure they are just as (un)likely as yours is.
What's the point here? Is this not common sense? Too much of anything is bad. Why bring complicated subjects radioactivity to this point when all you need to do is use the example of water, ie: you can die from consuming too much water, and it is called water poisoning.
Is your point merely that everything is Schrödinger's chemical unless we study it? That is a stupid stance. This article is clearly associating a = b+c, ie: this chemical is causing bad things for your intestinal microbes which leads to diabetes, etc.
I feel like you are maliciously attempting to downplay the severeness of the studies' results by introducing the Schrödinger argument. I am calling the quote by ET Jaynes to be pointless and equating his example of radioactivity to the aforementioned water example.
With this equation in mind, are you trying to say that a small dose of our insecticides is good for us, but, we are abusing it? Do you have any grounds for this? Even E.T Jaynes implies there is no proof for this statement because of the lack of studies. Why would you downplay this?
Indeed it is the age old idea of "the dose makes the poison". What Jaynes is saying is a bit more than that though. Most people assume toxic chemicals have a linear response. If you take half the poison, it will still have 50% of the effect of the full dose. Jaynes argues this model is completely wrong and under a certain threshold there is basically no effect. If you look at a study of people or animals exposed to high doses of pesticide, it doesn't really tell you anything about normal people exposed to much smaller doses.
More than that, he is saying there is a double standard for synthetic substances.We treat them with much more fear and caution than the natural chemicals we are exposed to all the time. Many common vegetables would not pass FDA requirements if they were "invented" today. They contain thousands of chemicals. Many of which have never been tested, and some of which are even known to be toxic. Like solanine.
That's great, but, not the subject of this post. We're not discussing the theory of whether new chemicals are good or bad. I agree with you that the general consensus is to overly fear man made chemicals, which is wrong and also stupid.
The issue I am having with the comment is that this is a specific study on a specific set of chemicals that produced a specific outcome. We're not discussing chemicals in general, and yet you are making it seem like the results of this study should be ignored because chemicals can be good and bad.
To draw a comparison, it's like someone posted an article about high concentrations of asbestos leading to health problems, implying that maybe we shouldn't use it as an insulator. It's not implying that we shouldn't use insulators. It's simply implying that maybe we should reconsider the use of this specific insulator. Then you come in commenting nonsense about how insulators are a good thing, and that we need insulators. The issue is that nobody is arguing against you. You're right that insulators are a good thing and necessary. The problem is that takes away from the main point of the article, that we should reconsider the use of this specific item.
The grandparent comment I replied to is literally about fearing man made chemicals in general.
>To draw a comparison, it's like someone posted an article about high concentrations of asbestos leading to health problems, implying that maybe we shouldn't use it as an insulator. It's not implying that we shouldn't use insulators. It's simply implying that maybe we should reconsider the use of this specific insulator. Then you come in commenting nonsense about how insulators are a good thing, and that we need insulators.
It would be more like if someone posted an article about asbestos, and the top comment was about how they strongly distrust all man made materials.
>A common error, when judging the effects of radioactivity or the toxicity of some substance, is to assume a linear response model without threshold (that is, without a dose rate below which there is no ill effect). Presumably there is no threshold effect for cumulative poisons like heavy metal ions (mercury, lead), which are eliminated only very slowly if at all. But for virtually every organic substance (such as saccharin or cyclamates), the existence of a finite metabolic rate means that there must exist a finite threshold dose rate, below which the substance is decomposed, eliminated, or chemically altered so rapidly that it has no ill effects. If this were not true, the human race could never have survived to the present time, in view of all the things we have been eating.
>Indeed, every mouthful of food you and I have ever taken contained many billions of kinds of complex molecules whose structure and physiological effects have never been determined—and many millions of which would be toxic or fatal in large doses. We cannot doubt that we are daily ingesting thousands of substances that are far more dangerous than saccharin—but in amounts that are safe, because they are far below the various thresholds of toxicity. But at present there is hardly any substance except some common drugs, for which we actually know the threshold.
The most dangerous substances fall into a few categories. Things like insecticides (which is what this thread is about) are designed to kill animals. Insects, but still, their physiology is close enough to humans. And things like heavy metals and radioactive substances. Which our ancestors weren't really exposed to.