Toxicology is a very interesting science.  The results are often surprising and unpredictable.  Yet, there are some truths that are universal.  One big truth is effects are never linear with dose.

What does non linear mean?  Well, assume I am testing some substance to determine its LD50.  I happen to find it takes a dose of 1 gram per kilogram of body weight in the test animal to result in a 50% death rate.  A linear response would say a dose of 1/2 gram per kilo of body weight would result in a 25% death rate.  Likewise a dose of 1/4 gram per kilo would result in a 12% death rate.  This is never what  is observed.  The death rate from a 1/2 gram dose could be 0%.  Or it could also be (rarely) 60%.  So, what is going on with those two numbers?  The zero might simply say that at less dose than the LD50 the stuff simply is not toxic enough to cause any deaths at all.  If you ran 1000 test animals you would see a few deaths, but not many.  Generally LD50s are run at something like five animals per dose level.  The 60% death rate is the real interesting number.  What this shows is there is always a difference in sensitivity to any test substance from one animal to another even in highly inbred strains.  This can be caused by small differences in how well the kidneys eliminate the toxin to subtle effects resulting from overall health to minor genetic or epigenetic differences that result in fairly large differences in the rate of metabolism of that particular substance.  As well as lots and lots of other things.

What is universal is you do not see a linear curve and if you test any dose below about 10% of the LD50 you see zero deaths.  But, with any substance you never know the shape of its particular dose response curve.  The shape is impossible to predict and equally impossible to predict outside the range that is actually tested.  In fact we know of lots of cases where a high dose of some substance is lethal, lower doses have either only minor or no impact on things like life expectancy or general health or weight gain or loss or reproductive capability.  And even lower doses become sub optimum for life and if not enough is consumed the result can be death again.  To be perfectly clear I am saying there are many substances where a high dose will kill you, an intermediate dose does nothing negative to you and a zero dose kills you.  Now anyone with a high school education knows this is true and knows of many examples.  If they do not know this and know examples they sure wasted their time and the public's money by going to high school.

The net result is LD50s are a fine starting point to get some crude idea of how toxic some substance may be.  Some sixty or so years ago it was thought if you did fine on some single dose smaller amounts given daily were ok as your body would deal with those smaller doses by elimination or metabolism.  While this seems logical it is not true.  Cumulative small negative effects that can not be detected in short term feeding studies can, given a long enough time, result in all kinds of damage.  And just like in short term tests there will be a big difference in results from test animal to test animal.  Such animal to animal variation is normal and expected.  Consider drugs your doctor gives you to improve your personal health as an example of such variation.  All drugs have side effects.  Every drug is aimed at whacking some biochemical pathway in your body.  The drug poisons that pathway either totally or partially.  Most people either do not experience side effects or those effects are livable when taking approved drugs.  But, for a few people the side effects can be a huge problem.  I am currently recovering from poisoning by a drug my doctor gave me to help control my atrial fibrillation.  I was on the drug and doing fine for three months.  I got up one morning and my fingers and toes were all tingly just like when you sleep on an arm and shut of circulation too long.  In about a week I no longer had much feeling in my palms and feet.  My finger nails hurt so bad they felt like they feel after hitting them with a hammer.  I have been off that drug now for six weeks.  My finger tips still tingle.  This side effect to this drug happens to less than 1% of the people put on it.  I can tell you no one is going to be willing to live with this side effect so it is not under reported.  There are lots of well documented examples of drug side effects from human meds.  Every single person that goes on a statin to control his cholesterol will have a loss of stamina within six weeks according to testing published in the medical literature.  Many people do not even notice the loss.  For some it is so bad it is horrid.  As a side note every statin also causes cancer in mice dosed to have about the same plasma level of drug as targeted in human treatment.  Yet, to date there is zero epidemiological data to show any excess cancers in humans.  The number of cancers is simply too small in humans to detect yet.  Given time those cancers may well show up when a lot of people have taken these drugs for forty years.  Then we may wonder why doctors in 2010 were handing them out like candy. And a bunch of people will sue hell out of the companies that produce them.  Pesticides are safer.  If a pesticide showed such cancers in any kind of mouse test the company would instantly kill the product.  I know this is true.  It is true because the law says such a pesticide can not be registered and I know it is true as I have been in the meeting when such a product was killed long before the product was registered much less sold to the public.

As science became aware of longer term negative effects of everything from natural products to pesticides to drugs the result was longer and longer term testing was instituted.  In 1950 thirty day tests were considered long enough.  Today that is at best a preliminary range finding point to determine a no effect level.  Today the meaningful studies are things like three generation studies or reproduction studies.  Plus we have all kinds of studies to look for things never dreamed of in 1950.  Things like mutagenicity studies or nerve damage studies or allergic promotion studies.  Not to mention long term studies aimed at determining if the substance can cause cancer at any tolerated feeding level.

When you hear claims that glyphosate might cause non Hodgkin lymphoma cancer at the allowed levels in food you are listening to a fool who is totally ignoring the mountains of data that says this idea is simply ridiculous.  That person more often than not will also tell you the ills of getting a flu immunization.  Remember, with glyphosate you are dealing with an inherently very non toxic substance.  It has an acute toxicity roughly the same as table salt.  What this means is you are able to feed really large amounts in chronic studies without killing the test animals.  This makes the carcinogenicity tests extremely sensitive.  If you have two substances which are equal in terms of causing cancer but one is 100 times more acutely toxic than the other your cancer test will turn up the bad character in the less toxic substance long before you see the slightest hint of cancer in the more toxic substance.

When you hear that neonics will  kill bees what do you expect?  Neonics were designed to kill  insects.  That is their only purpose.  Bees are insects.  If you think we should regulate neonics to such levels that bees can not be harmed you are also claiming they should only be applied at such low levels that they can not kill the target insects either. 

Now, I realize there are people who oppose any pesticide use until they want to use a pesticide.  So called "organic" farmers fall in this class.  They often hide behind the nonsense that they only use safe natural pesticides.  There are lots and lots of natural pesticides.  Nature has been making them for billions of years.  They are very good killers quite often.  Nicotine itself is a fine example.  So are things like ergot or aflatoxin, which by the way are a greater risk of being in "organic" food than in that bad chemical food that comprises the vast majority of the food humans consume.

I do not want my bees to be killed by pesticides.  So, I use stuff that is safe around bees or use stuff that is unsafe around bees in a way that my bees do not get exposed.  I do not have the slightest concern I will harm my bees when I spray RoundUp right up next to the hives to control weeds.  I do not have the slightest concern I will harm my bees when I pour neonic granules down the hole on a yellow jacket nest a few feet from my hives as I promptly put a board over the hole until the next rain.  I do not have the slightest concern when I spread some season long ant killing granules around my bee yard in Feb when there is six inches of snow on the ground to control small hive beetles the following summer.  Bees lived with pesticides long before any chemical manufacturer sold the first pound of synthetic bug or weed killer.  Keeping your bees safe is mainly a mater of reasonable education and common sense which are both often sorely lacking today.

Is my thinking at all novel?  Not at all.  One of the main founders of the environmental movement, Rachel Carson, would agree with what I have said.  She considered "organic" farming to be pure nonsense as it was destructive to the environment compared to alternatives and also unable to produce enough food to feed the world. She was not anti pesticide.  She was in favor of careful testing to insure safety and careful limited use to protect the environment.  She was right.  And, we have come a long ways in part as a result of her forward thinking.  We have farther to go.  I personally am opposed to any chemical uses of any type on lawns.  That includes putting fertilizer on lawns.  Yet lawns and grassed areas are major consumers of pesticides and fertilizers today.  A total unneeded waste.

Dick

HL Mencken said: "The whole aim of practical politics is to keep the populace alarmed — and hence clamorous to be led to safety — by menacing it with an endless series of hobgoblins, all of them imaginary. "

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