WHAT WE KNOW ABOUT PESTICIDE RESIDUES IN FOOD

Pesticides are used to selectively control a variety of biological pests such as insects, weeds, rodents and moulds. Although they are not meant for human consumption, their pattern of use and distribution in the environment means they find their way into food and water. The main pesticides of concern are the organochlorines such as DDT, dieldrin, and lindane (because of their extreme persistence and accumulation in the environment and food) and the organophosphorus compounds such as malathion and parathion (because of their high toxicity).

Health authorities have established maximum limits on the level of individual pesticide residues in the diet that are considered to be safe for the general population. These limits take account of the joint need to provide an adequate, economical and wholesome food supply. The health risk to the consumer from trace levels of pesticides in the diet is small. Even if an occasional food is in excess of the acceptable limit, there is a sufficient built-in margin of safety to ensure that there is still little likelihood that it will pose a threat to health. It must be recognised that some older pesticides when re-evaluated using contemporary safety standards may be identified as potentially carcinogenic or in some other way hazardous to humans or the environment and that prompt action by regulatory bodies to reduce such risks needs to be taken.

Australia has been monitoring pesticide residues in food since 1970. When pesticides are used in the manner and quantities recommended on their labels, any residues should be within acceptable health limits. However, crude 'bucket and shovel' methods, inappropriate application rates and shortening of withholding periods can result in unacceptably high residues in food. A thorough program of monitoring is essential if such foods are to be detected. Since monitoring began, developments in analytical chemistry have resulted in the detection of residues in ever decreasing amounts. Residues once not detectable are now being found using newer, more sensitive analytical methods. However, the ability to detect these minute amounts has outstripped the ability of toxicologists to predict the health significance of such low levels of exposure.

There may be some people in the community who are sensitive to a pesticide or who are exposed to higher amounts because they have unusual diets or consume large amounts of particular foods. It would be prudent for such people to minimise exposure by washing fruits and vegetables or removing peel, outer leaves or excess fat before consumption. Cooking may lower the pesticide load even further. Where food is produced in home gardens using pesticides, it is important that all instructions on their use be followed, particularly the time between its application and harvesting in order that any residue is minimised.