SINGAPORE - Most of us buy conventionally produced food most of the time. But organic food has been growing in popularity among people who believe, among other things, that it is largely pesticide-free.
Their faith is such that most are likely to disregard any study that provides evidence to the contrary. These believers might be gladdened by a new study just published in the British Journal of Nutrition, which finds that organic food indeed has less pesticide residue than conventional food.
Led by Newcastle University dons and partially funded by the British organic sector, it reviewed 343 studies of widely varying quality. However, it would be scientifically more precise and intellectually more honest for the study to conclude that organic food has less "synthetic" pesticides.
All farmers have to deal with pests. Conventional farmers use synthetic pesticides, which organic farmers are not allowed to use.
That is why many people think organic farmers use no pesticides at all. Many believe that, eschewing synthetic pesticides, organic farmers rely only on careful crop selection, crop rotation, manure, insect traps and composting, as well as biological pest controls such as predator insects and beneficial micro-organisms.
Unfortunately, these methods are not always enough. So pesticides remain necessary - thus creating the organic food industry's dirty little secret.
It is a little known fact that organic farmers use lots of pesticides that are described as "natural" or "organic". Unfortunately, organic pesticides can be as toxic as synthetic ones, or more so.
So while organic food might indeed have little or no synthetic pesticides, as the study found, it is likely to contain more organic pesticides that are potentially harmful chemicals.
The Newcastle University study looked at only synthetic pesticides, not organic ones.
There are 200 disparate certifying bodies for organic food in 80 countries, each setting its own standards. Generally, none of them test for levels of organic pesticides.
As it is largely a self-regulated sector, organic certification requires only that farms show a system plan and keep compliance records. Field testing for compliance is rarely carried out. And no government requires any organic farm to record the actual amounts of synthetic or organic pesticides used.
Because of the fallacy that "natural" is good, even scientists have rarely looked for natural pesticides in organic food.
But in a publicly funded 2009 study as well as two others in 2010, United States scientists found measurable traces of either natural or synthetic pesticides, or both, in 15 per cent to 43 per cent of organic produce, depending on which farms were sampled.
One positive feature of organic pesticides that has little to do with food safety is that they degrade faster in the environment.
So they pollute water and land a lot less than synthetic pesticides do. But because they degrade faster, a lot more has to be used. In contrast, synthetic pesticides are usually more effective at lower doses.
A 1990 study published in the Proceedings of the National Academy of Science found that up to seven applications of a mixture of rotenone and pyrethrin - two popular organic pesticides - were needed to obtain the same level of protection against pests as that provided by two applications of imidan, a pesticide synthesised to degrade as fast as organic ones.
If organic pesticides must be sprayed more often, organic food might well have lots of these pesticide. Some could be safer than synthetic ones, but not all are.
Take rotenone, a widely used organic pesticide. Derived from a few sub-tropical plant species, it is poisonous to nerves or nerve cells. Indeed, it has been found to cause Parkinson's disease in laboratory mice.
The US Environmental Protection Agency has found that the safe level of daily exposure for humans is under 0.004mg per kg of body weight.
By comparison, that for glyphosate, a widely used synthetic pesticide usually sold under the brand Roundup, the safe level is below 0.1mg per kg of body weight.
That means natural rotenone is 25 times more harmful by weight than synthetic Roundup.
Another widely used organic pesticide also poisonous to nerve cells is pyrethrin. Derived from chrysanthemum, it is also more toxic by weight than Roundup.
In organic farming, "natural" copper salts and sulphur are widely used to deal with fungi. This is because fungi produce toxins, including aflatoxin. Found on mouldy peanut skin, aflatoxin is known to cause liver cancer.
But how much copper or sulphur is bad for humans has not been definitively established.
In sum, "natural" might not be non-toxic, and "organic" is not unequivocally safer.
What the "organic" label means is that the producer claims to have adhered to some process standards in production, handling, processing and marketing.
So "organic" is merely an ethical claim about the process, not one about the product.
Now you know organic pesticides might be found in organic food, and these could be worse than synthetic pesticides, what can you do with this information?
Not much, if you are thinking of checking for pesticide content in organic food, since no certification board mandates it.
Moreover, the difference in levels of synthetic pesticides in organic and conventional foods is not large. And the level of pesticides even in conventionally grown produce is already way below permissible levels.
For example, a 2011 study published in the Journal of Toxicology found that one must eat 787 conventionally grown apples in a day to ingest a toxic amount of thiabendazole, a synthetic pesticide used frequently at apple farms.
What all this means is that buying organic food in the belief that doing so will save you from ingesting pesticides makes little sense.
Anyway, rinsing any produce thoroughly gets rid of most pesticide residues. So eat lots of produce, whether organic or not.
This article was first published on Aug 9, 2014. Get a copy of The Straits Times or go to straitstimes.com for more stories.