This article was first published in 听
The most commonly stated reason people buy organic food is avoidance of pesticide residues. Indeed, organic producers cannot use conventional synthetic pesticides, but that does not mean no pesticides are used. Soap-based herbicides and insecticides such as boric acid, lime sulfur, elemental sulfur and various oils are allowed. So is copper sulphate since it occurs in nature, although for agricultural use it is synthetic, made by reacting copper oxide with sulphuric acid. Curiously, the bacterium, Bacillus thuringiensis (Bt) is allowed for caterpillar control, but crops that have been genetically engineered to produce the toxin the bacterium uses to kill caterpillars are not allowed.
A variety of chrysanthemum grown mainly in Africa contains pyrethrins, chemicals the plant uses as protection against insects. A bug that dines on the flower鈥檚 leaves learns what indigestion is all about and looks elsewhere for its next meal. Organic farmers make use of this repellant effect by spraying crops with commercially available natural pyrethrins. But does the fact these substances are natural absolve them of potentially harmful effects? Not at all. Natural compounds can be every bit as dangerous as synthetics. Exposure to high doses of pyrethrins can cause neurological symptoms and has also been linked to liver tumours in mice and rats.
Now here is the kicker to this little story. Chemists have been able to improve upon natural pyrethrins. The molecular structures of these compounds have been determined and analogues that differ only slightly in structure have been synthesized. These are more powerful insecticides, meaning smaller amounts can be used, which, in turn, means a reduction in risk. But these modified pyrethrins cannot be used by organic farmers because they are synthetic.听
Not to worry though. All pesticides, whether synthetic or natural have to pass the stringent safety and efficacy requirements set up by Health Canada. This begins by reviewing studies in which animals, commonly mice or rats, are fed a pesticide in increasingly larger doses. Then the highest level given on a daily basis throughout an animal鈥檚 life that does not cause any noticeable toxicological effect is determined. This is known as the No Observed Adverse Effect Level or NOAEL. Dividing this by a factor 100 leads to the Acceptable Daily Intake (ADI), which is the amount of a pesticide a person can safely consume every day throughout life.
To ensure people consuming a normal diet do not exceed the ADI for any pesticide, Health Canada sets Maximum Residue Limits (MRLs) for pesticides in foods. This involves field trials in which grains, legumes, vegetables and fruits are treated with the pesticide in question at the maximum approved rate and the amount of residue present when the food is ready to be consumed is determined. The MRL for each pesticide is then set in a way to ensure the total amount of that pesticide in a standard diet is less than the ADI.
The Canadian Food Inspection Agency (CFIA) is charged with carrying out random tests for pesticide residues on foods, including imported ones. Only about 2 per cent of samples are found to exceed the MRL for a single pesticide, but that is of no consequence because of the large safety factor built into the ADI. Still, every year, the Environmental Working Group (EWG), an advocacy organization in the U.S., comes out with a warning about the 鈥淒irty Dozen鈥� fruits and vegetables that contain the most pesticide residues. The EWG defines most as the number of different pesticide residues, not their amounts. What matters is not how many different residues are present, but whether these exceed the MRLs. The fact is 98 per cent of the residues are below the MRL, which means describing these fruits and vegetables as 鈥渄irty鈥� is dirty.
Even though our food supply contains only traces of pesticides, some consumers still prefer organic. To make sure they are really getting what they are paying for, they look to Canada鈥檚 seal of organic certification. The natural assumption is the seal on a package is a guarantee the rules of 鈥渙rganic鈥� food production that prohibit synthetic pesticides and fertilizers, GMOs, antibiotics and hormones are followed. But that may not actually be so, because as surprising as it might be, organic certification is not actually carried out by the government and does not require testing for prohibited substances.
The CFIA is charged with looking after the safety of our food supply, but when it comes to organic certification, the responsibility is passed off to private certification agencies that have been approved by the CFIA. Growers looking for organic certification pay a fee to these agencies to get a seal of approval. What is involved? Basically, an on-site inspection and some paperwork. Forms are filled out attesting to the fact organic regulations are abided by. No sampling is done to check for pesticide residues or to see if compost is free of pathogens. It is an honour system. The same applies to imported produce, and about 80 per cent of organics sold in Canada are imported.
Some consumers seek out organic foods believing them to be more nutritious. Often, they have been seduced by allegations conventional agriculture has robbed the soil of nutrients, or they may have heard organic crops have to produce more natural pesticides since they are unprotected by synthetic ones. These natural pesticides are in the form of polyphenols, compounds that also happen to be antioxidants with the ability to protect us from those rogue undesired byproducts of metabolism, the nasty free radicals that conspire to undermine our health.
Numerous studies have compared the nutritional qualities of conventional and organic foods and concluded while organic produce may contain slightly more polyphenols, the difference within the context of an overall diet is insignificant. What is not insignificant is the overwhelming evidence eating a diet rich in fruits, vegetables and whole grains is vastly more important than whether those foods are organic or conventional.
