The Swedish chemist Berzelius coined the term “organic” for substances that could only be made by living organisms and not synthesised by humans. His German friend Wöhler synthesised urea in 1828 proving Berzelius wrong: there was no such distinction. Another brilliant German chemist, Liebig, then used “organic” to mean carbon-compound chemistry, extending this to include the chemistry of living organisms and so beginning biochemistry.

Liebig started another new science: agricultural chemistry. He showed that plants extracted only simple chemicals from the soil and from these built complex substances. He advised farmers to return animal and plant waste to the soil (including human waste) but also to add simple chemicals as supplements.

Liebig disputed the theory that plants obtained their nutritional requirements from soil humus – a cornerstone of vitalist theory – and showed experimentally that this was not so. The vitalists, who later developed into the early “organic” movement, regarded Liebig as their arch-enemy, and being a naturally quarrelsome person he enjoyed this. They seized upon his errors; some of his artificial fertilisers were insufficiently soluble to be readily available to plants. Further he was misled by work on peas and beans to believe that plants can readily obtain nitrogen from air. No plant can do this but some (such as peas) have symbiotic bacteria in root nodules, which can “fix” atmospheric nitrogen and make it available to the plant.

In my youth the organic movement still held to the doctrine of vitalism; that living things are completely different to those non-living and thus not subject to the laws of physics and chemistry. Those who demand that food be free of “chemicals” are rejecting science in this tradition.

Until recently, “organic” farming and gardening meant using no inorganic chemicals as fertilizer, only natural manures. It was simply opposition to the discoveries of Liebig and denial of an important part of science. The theory was silly but the practice less so; improving the soil structure with compost can improve yields. The addition of nitrogen-containing fertilisers increases the rate of decomposition of humus. This can damage soil structure, as the organic movement claims, but organic urea does this as efficiently as inorganic ammonium compounds.

Today the organic movement concentrates on growing plants without using “artificial” chemicals, but their list of prohibitions is ad hoc. Derris and Pyrethrum are “natural” and thus acceptable but other chemicals that have long been used seem accepted even if “artificial”. Chemistry does not accept a distinction between “natural” and “artificial”, so framing laws to ensure “organic” produce is according to label is extremely difficult.

Liebig’s theory led to hydroponic growing. No soil, no humus, just a solution of inorganic chemicals as plant nutrients. Greenhouses sealed against pest entry do not require spraying (although outbreaks occur occasionally) so in America, hydroponic produce is being sold as “organic”. In NZ such produce does not meet the standard set by the organic product licensing agencies although it could be sold here (where anything goes) as “organic”. However if New Zealand-licensed “organic” crops are exported to the US, they will have to meet competition from hydroponically home-grown “organic” crops.

Derris is not very toxic to mammals but toxic to fish; run-off can badly effect aquatic environments. Pyrethrum is not very toxic to mammals or insects, although it has a spectacular quick-knock-down effect. Affected flies drop on their backs and flail helplessly with their wings, then recover. To increase toxicity a synergist is added but this is an irritant to many humans.

Synthetic relatives of Pyrethrum were produced which need no irritating additives (low allergenic flyspray). They are no more toxic to humans but very toxic to insects. As they are “not natural” they are unacceptable to the organic movement. Yet natural Pyrethrum with artificial synergist is acceptable. This makes little sense.

The organic remedies section in garden centres contains an odd assortment. Pyrethrum with added synergist is there, as is “garlic and pyrethrum”, (which should be more acceptable to the purist). Most gardeners like myself prefer synthetic pyrethroids, no more toxic, more effective, and safe when used sensibly. Bacillus thuringiensis used to be there (it is still acceptable on commercial organic crops) but it disappeared after claims of health problems following the spraying of suburban areas in Auckland to eliminate an introduced moth.

Some organic growers use copper compounds as fungicides (a chemist finds it ironic to see inorganic chemicals passing the “organic” test) and copper, though an essential part of our diet, is toxic at low concentrations. The safest form is copper oxychloride but this is not acceptable to the licensing authorities; instead they permit Bordeaux Mixture, (copper sulphate and lime) which was invented in the 19th century. Copper sulphate is such a common substance that it is not scheduled as a poison yet its toxicity is so high that if taken orally it is lethal at a dose that would put it into this classification.

Practically all the chemicals used by home gardeners these days are so safe they are not classified as poisons, but fall into the less hazardous category of “harmful substance”. Copper oxychloride is less dangerous to the person applying the spray than Bordeaux mixture, and is less persistent as a spray residue, than Bordeaux mixture, but as it is a 20th century invention it is not acceptable. This makes no sense at all.

Older gardeners will remember being asked to sign the Poisons Book after a purchase at a garden centre, but they could buy really dangerous chemicals: strychnine, paraquat, mercury chloride or lead arsenate. The substances sold today in garden centres are unlikely to be fatal even if used carelessly.

According to Green propaganda, fruit and vegetables we buy in supermarkets are “drenched with chemicals”. Certainly they carry pesticide residues but do these represent a danger? There is anger that the allowable quantity of Roundup (a trade name for glyphosate) residue has been increased for some food substances: “They are now allowed to put 400 times as much Roundup in our Canola oil.” (I heard this on the radio from an outraged person.) But the allowable quantities are still minute and Roundup is not very toxic. The acute oral LD50 is 5400mg/kg for rats, which means than when a group of rats were each fed that amount about half of them died.

How they were got to consume so much defies imagination; it is equivalent to me drinking more than a litre of the concentrate – and remember around half of them survived. A lot of the substances we eat every day are much more toxic. When I was at school a fellow pupil tried to consume the contents of a salt cellar for a bet and it very nearly killed him. Common salt is much more toxic than Roundup.

Researchers at Lund University in Sweden have linked Roundup to the increase in non-Hodgkin’s lymphoma (73% increase in the US since 1973). There is reasonable correlation; the use of Roundup has certainly increased in parallel, but consider all the other possibilities. Use of personal computers, digital wristwatches, Japanese cars, and consumption of kiwifruit. Correlation does not equal cause.

The organic movement is less concerned with the acute effects of pesticides than their long-term effects when consumed at low levels. It is of course impossible to prove that there are no bad effects, but this is true of “organically grown” produce also. The distinction between “safe” and “toxic” is false. All chemicals are harmful if ingested in too great quantity (although it is impossible to ingest enough of some substances to reach the harmful threshold). Vitamins are highly toxic if taken in excess and an excess is still a very small quantity. They are essential in our diet but if a little is good then a lot is not better.

Jay D. Mann wrote an excellent article on toxins in food and their associated risks [NZ Skeptic, 19 March 1991]. He warned against demands for zero levels of residues on food, but that is just what is now being demanded. He also suggested a sensible policy for assessing risk and pointed out that nothing is ever safe. Now we have demands that foods be proved safe: “No Genetically Engineered food until it is proved safe.” This effectively demands the proof of a negative – that a product will never cause any human any harm – and it is impossible.

Many food plants have been produced by breeding cultivars lacking natural protective toxins. This makes them safe to eat but more vulnerable to pests. Modern plant breeders, finding many wild plants were pest-resistant, responded by producing cultivars that were so resistant to pests that spraying was unnecessary. This is fine for a crop like cotton which is not eaten, but many such new pest-resistant cultivars of food plants proved too toxic for human consumption. Living organisms make some of the most toxic chemicals.

The New Zealand Health Department sets standards for the acceptable levels of toxins in or on food sold in New Zealand. In most cases there is an enormous safety margin, so that consuming produce with unacceptable toxin levels will generally be hazardous only if this is done regularly over a lengthy period. If toxic residues provided the degree of risk to young children that is carried by food with ordinary levels of salt or sugar, they would probably attract the attention of Holmes.

For food sold as “organic” in New Zealand there are no standards at all. But why should organic growers be more honest than those dreadful multinationals? New Scientist reports that several examples of genetically engineered food were found when a range of produce was tested in a Health Food shop.

“Organic” food producers have organisations that will certify their produce is grown correctly. These are Bio-Gro NZ, and Demeter (the latter is part of the Rudolph Steiner biodynamics organisation). This mostly applies to food grown for export. A farm or orchard has to meet certain standards over a period of years before it gets certification. The producer then expects to obtain higher prices.

Bio-Gro states that it “inspects and verifies its licensees” but it does not claim to test for spray residues. Producers include Heinz Wattie Australasia, Talleys, and McCain Foods. Some pretty big names there – even some multinationals! “Organic” produce is not just sold by the little people. Big business has sensed a commercial opportunity and is cashing in.

Bio-Gro NZ “makes allowances for growers during the often difficult transition from conventional to organic production”. “Semi-Green produce” commands a lesser premium than fully certified product. Again Bio-Gro NZ is concerned only with the production methods, not with testing. This is not surprising given the dogma that treatment with some chemicals is safe, while treatment with others is hazardous; the distinction between such chemicals is ideological not scientific.

Organic production is incapable of feeding the present world population – a fact which is obvious in many highly populated countries (though not in New Zealand). And organic food is more expensive; poor people cannot afford it.

There is a lot of publicity claiming that “organically” produced food will be the mainstay of New Zealand’s exports in the future. However, the purist European Greens are entirely opposed to international trade in food, whether or not it is grown organically. Those who have seen opposition to international trade expressed at APEC will not be altogether surprised.

Children in parts of rural England used to get time off school for spud-harvesting. A spinner turned the potatoes out of the ground, which were then picked up by hand and bagged. First, however, the field was sprayed with haulm-killer (an arsenic compound) to make the tops die down and facilitate the harvest. The residue was confined to potato skin and as English people did not eat this it did not seem to matter. Imagine my horror when going to Scotland as a child, I found I was expected to eat potato skin – I knew it was deadly poison! After a few years the stupidity of allowing arsenic to accumulate in agricultural soils was realised and the practice stopped.

The Christchurch Botanical gardens stopped using Benlate because a worker’s child had a birth defect and in America a group had successfully sued Du Pont after children had been born with birth defects. This was an example of what Scientific American called “Junk Science in the American Courtroom” and the case was overturned on appeal. Actually, Benlate is a fungicide of such low acute toxicity that it has not been measured, because it proved impossible to feed enough to rats to kill 50% of them.

Bio-Gro NZ rules permit the application of limestone, gypsum, and rock-phosphate as fertiliser (providing calcium, sulphur and phosphorus as plant nutrients), yet these were not classified “organic” by either Berzelius or Liebig and the early organic movement found them unacceptable. Liebig would have had a good laugh.

Bio-Gro are aware of the dangers in using compost as fertilizer and state that “plant material and animal waste from conventional sources must be hot composted”. The (unstated) reason is that persistent pesticides go through animal intestines and compost heaps. However hot composting does not remove them completely, though it may reduce the concentration and there is no known danger to humans in eating produce grown in such compost.

Micro-organisms consuming nitrogen compounds produce heat in a compost heap. The easiest way to heat up a sluggish heap is to put a handful of urea pellets on top and water in (do try this at home, or rather in the garden). This is not acceptable to the organic movement if “artificial” urea is used, though animal urine is allowed. But no heap is uniformly hot, it will always be sufficiently cool in places that even some weed seeds survive. The most persistent pesticide molecules are herbicides. Fortunately, most modern versions are not very toxic; the most toxic are cocktails which include long-used chemicals such as 2,4-D. If plants which have been sprayed are grazed or composted, the herbicide may have an effect on another generation of plants.

The “Tordon effect” occurs when horse manure is used as a fertilizer after the animal has grazed plants treated with the herbicide Tordon. The animal is unharmed but serious damage can be caused to the manured crop. Hot composting (and nothing heats better than horse manure) may reduce but not eliminate this problem.

A Nelson commercial flower grower reported crop damage over three seasons. Eventually this was traced to use of pea straw as a mulch, the pea straw carrying residues at a very low level.

These examples might be thought to show the organic movement is correct, but they illustrate some dangers of using persistent pesticides and no harm has occurred to humans. They illustrate the fallacy of distinguishing between “natural” and “artificial”.

DDT was a particularly persistent insecticide, which eventually broke down to harmful products. Organophosphate insecticides that rapidly broke down to harmless products replaced it. Early examples were highly toxic to animals but safer examples have been produced. The chemical industry has responded to pressure by producing safer pesticides but the organic movement has ignored this.

There is an alternative to “organic growing” and one that is science-based rather than anti-science. This is Integrated Pest Management (IPM). The philosophy behind this is:

  • to choose the best methods of pest control from the full range of available techniques
  • to minimise the amount of agrichemicals used (on economic grounds among others)
  • to use non-persistent chemicals, and to avoid contamination of, soil, water and air
  • to avoid killing non-target organisms
  • to sell produce with a minimum of pesticide residues

IPM monitoring systems show when pesticides are needed, rather than their being applied according to the calendar. In Nelson there is a mite-forecasting service which shows when build-up of this pest necessitates control measures. Biological control and pheromone traps are used when possible. Broad-spectrum pesticides are avoided, as these kill predators alongside the targets. Food produced in this way cannot be sold at a premium so it is no more expensive. Is it not a pity that sensible, science-based methods of food production are unlikely to inspire the support of a political party?

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