While herbicide-resistant or pesticide-making crops may have benefits for the producer, it's the potential side effects for the consumer that has Carman worried. One reason is because grub-killing (pesticide-producing) crops have been genetically engineered with a Bt (Bacillus thuringiensis) gene, which means the plant makes the pesticide internally - and it cannot be washed off. "If you spray a (non-GM) plant with pesticide or a herbicide, you're not allowed to harvest it and market it for a certain period of time to give the chemical time to decay, (but with pesticide-resistant GM crops) there's no withholding period ... and the pesticide is in every cell of the plant, so you eat it."

Carman says GM foods have not been around long enough for anyone to know what health problems they may cause, no one is looking at health surveillance systems to see if GM foods are currently causing harm, and no real animal or human studies have been done on their long-term effects. In light of this, Carman says it is difficult to know what the future health effects of GM foods may be. Some of the concerns include an increase in allergies; an increase in herbicide residues in food; a worsening of antibiotic resistance in intestinal bacteria; reproductive problems; and genetic modification causing a plant to produce an unknown toxin which might have toxic effects on the body's organs.

Carman says while there may not be any detrimental health effects in the future from GM foods, no one really knows the truth because GM foods have not been tested adequately before appearing on supermarket shelves. "The worst case scenario is that something bad could go wrong - some horrible health effect and we wouldn't know about it for years," she says. Carman uses the example of a North American farmer who fed his pigs GM corn, and found the pigs couldn't get pregnant. But when he later fed them non-GM corn they had their fertility back. "If something similar happens in the human population, and I'm not suggesting it will, we may not know for a long time until we see infertility rates rise. By then it may be too late, because by then it may be impossible to remove the crop from the food supply. Remember that once they got established, we couldn't remove cane toads or rabbits from the environment."

Greenpeace GM campaigner, Louise Sales, says consumers who choose to buy non-GM foods can find it difficult because of the labelling laws. While a food, food ingredient, additive or processing aid containing novel DNA or protein that has come from an approved GM food must be labelled with the words 'genetically modified', there are some exemptions. "Some fryers might use GE cotton seed oil because it's cheap, and unfortunately they don't have to label it in Australia. Highly processed GE oils, and GE food sources used in fast food and restaurants don't have to be labelled," Sales says. In addition, foods in which GM ingredients are present, accidentally and make up less than one per cent of the final food, do not have to be labelled. Sales also says labelling laws are not enforced. "We're campaigning to get labelling laws tightened as consumers have a right to know if the food they're eating is GE or not," she says.

Sales says she is also campaigning for Australian states to keep the moratorium on GM foods, which expires next year. "Our major concern is Australia's on the brink of losing its GE-free status if these bans (moratoriums) are lifted. If consumers want to maintain a GE-free food supply in Australia, they should write to their MPs and let them know what they think, and put pressure on their state governments to do the right thing by consumers."