Wednesday, April 02, 2008

Healthy small doses of poison & filth

I have long been interested in the phenomenon of hormesis and teach this topic to environmental economics students. This idea – developed by toxicologists – suggests that low concentrations of certain apparently dangerous substances (gamma rays, dioxins, even pesticides), may be good for your health. The health damage function is therefore J or U-shaped in levels of the toxin. Damages are high at zero concentrations of certain compounds and high (indeed higher) at high concentrations. But at small enough concentrations the damages are lower so that it is best from a health perspective if you are exposed to some of the compounds.

My intuitive reasons for being interested in this link is that kids seem increasingly vulnerable to allergies and asthma even though mum washes them and everything around them to be as spotlessly clean as Kevin Rudd's ear canals.

After a recent class where I talked about hormesis one of my students put me onto the related idea in a recent issue of New Scientist of ‘Fighting Cancer with Filth’. The gist of the article is that ‘researchers are starting to wonder whether the higher incidence of certain cancers in affluent populations - including breast cancer, lymphoma and melanoma - might also have something to do with sanitised, infection-free living’ so that ‘If we can understand exactly what it is about some germs that has a protective effect, we should be able to reduce people's risk of developing certain tumours later in life by exposing them to harmless microbes.’ ‘The simplest explanation is that exposure to viruses and bacteria - through infections, vaccinations or proteins such as endotoxin - stimulates the immune system and boosts its anticancer activity’. ‘As long ago as the 1970s it was noticed that workers in cotton factories have surprisingly low rates of lung and some other cancers. One explanation is that they owe the favour to cotton dust. This contains lots of endotoxin, a lipopolysaccharide found in the cell walls of many bacteria, which might keep the immune system on high alert.’ ‘The simplest explanation is that exposure to viruses and bacteria - through infections, vaccinations or proteins such as endotoxin - stimulates the immune system and boosts its anticancer activity. This makes sense, since we now know the immune system plays a bigger role in battling cancer than previously thought, destroying many tumours at an early stage or keeping them in check’.

There is even evidence that dairy workers who breathe in dried cow dung dust have a lower incidence of long cancer. There are even suggestions that injecting certain bacteria and viruses might cure cancer or even treat depression.

Hormesis arguments are hypotheses about behaviour but interesting ones. The implication of these ideas for the management of risk in relation to exposure to toxic substances, however, is huge. The dose-response relationship may need to be rethought in connection with the management of both dirt and toxins.

In addition the scorn conventional medicine has toward homeopathy may need to be rethought.


Anonymous said...

Hi Harry, Hormesis is interesting. Homeopathy is garbage. Conventional medecine is right to scorn homeopathy. Go to for more on why homeopathy is voodoo. The following is from quackwatch: "Homeopathic products are made from minerals, botanical substances, and several other sources. If the original substance is soluble, one part is diluted with either nine or ninety-nine parts of distilled water and/or alcohol and shaken vigorously (succussed); if insoluble, it is finely ground and pulverized in similar proportions with powdered lactose (milk sugar). One part of the diluted medicine is then further diluted, and the process is repeated until the desired concentration is reached. Dilutions of 1 to 10 are designated by the Roman numeral X (1X = 1/10, 3X = 1/1,000, 6X = 1/1,000,000). Similarly, dilutions of 1 to 100 are designated by the Roman numeral C (1C = 1/100, 3C = 1/1,000,000, and so on). Most remedies today range from 6X to 30X, but products of 30C or more are marketed.

A 30X dilution means that the original substance has been diluted 1,000,000,000,000,000,000,000,000,000,000 times. Assuming that a cubic centimeter of water contains 15 drops, this number is greater than the number of drops of water that would fill a container more than 50 times the size of the Earth. Imagine placing a drop of red dye into such a container so that it disperses evenly. Homeopathy's "law of infinitesimals" is the equivalent of saying that any drop of water subsequently removed from that container will possess an essence of redness. Robert L. Park, Ph.D., a prominent physicist who is executive director of The American Physical Society, has noted that since the least amount of a substance in a solution is one molecule, a 30C solution would have to have at least one molecule of the original substance dissolved in a minimum of 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 molecules of water. This would require a container more than 30,000,000,000 times the size of the Earth". cheers Geoff.

Anonymous said...

Just as in biodynamics, I think there is probably a grain (no pun intended) of truth in each of these principles. But I am not sure that correlation is causation, eventually. What application does all this have to Economics?

hc said...

Lesley most optimal pollution control models in economics use dose-response models that suggest total cleanup is optimal if ceanup costs are low enough.

The hormesis models suggest vthat leaving a bit of pollution might increase welfare.

One practical application is to limit the fears women have towards mammograms which test for breast cancer. Some women believe such inspections might increase their cancer risks. The hormesis literature suggests this is false - a bit of radioactivity is good for you.

Of course it is only a hypothesis - but an interesting one with practical importance.

hc said...

Geoff, I wasn't literally supporting the claimds of homeopathy. I agree much of the work is foolish quackery.

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Anonymous said...

The hormesis model is interesting and not really all that new. I'm hoping that it work as I spent my life until about 22 on a dairy farm, breathing in everything, killing our own meat, hanging it i na tree as we had no electricity initially, working with hands and clothes covered in cowshit and spraying weeds (and myself) with agent orange.

So far so good - no cancer, no asthma.

But Harry you suggested that science will have to re-evaluate homeopathy - I think I see a correlation or even causation in your thinking and drinking.

When did you give up the slops?

Feeling sympathetic to homeopathy is a bad sign - my advice harry - get back on the turps as quickly as possible.

To help I'll bring you back a carton of Long Life cigarettes from Taiwan.

Anonymous said...

How does this differ from the old idea that the reason adults in developing countries are so resistant to everything is that they were exposed to everything as infants? Some died, the rest are resistant; it's a selection effect.

That's why polio paralysis was a disease of the developed world - in poor countries they were exposed very young to the virus and tended to either get a mild case or be killed by it (seriously paralysed infants do not live in such societies).

Anonymous said...

Hormesis applies to government and taxation. A little bit is good. Too much is toxic.

Anonymous said...

The homeopathy-hormesis link is highly suggestive, notwithstanding the skeptic dogma that there is no rationale for homeopathy. While many homeopathic remedies rely on placebo alone (where high dilution means there are no molecules of the active substance at all), there may well be some truth to the basic homeopathic principle of similars. The field of evolutionary medicine demonstrates that clinical indications that were once thought to be damage (ie a fever) are in fact actually adaptive mechanisms (fever reduces the ability of some bacteria and viruses to propagate). Traditional medicine attempts to treat the symtom (ie reduce a fever with aspirin). In the light of evolutionary medicine such an approach may be counterproductive. A substance that promotes fever in small doses (ie a homeopathic remedy) makes sense in this context.