"Pesticides which are currently used are very safe but should ALWAYS be handled with great care" Pesticide toxicity Before any pesticides can be sold in Australia, they must be thoroughly assessed by the National Registration Authority. Pesticides are assessed for their acute toxicity (immediate effect), long-term toxicity, cancer causing potential and effect on offspring. Rats are used in toxicity studies because they can be fed a similar diet to humans and are used internationally as standard laboratory animals in toxicology research. Since the results of animals and rats may be different, an additional safety factor is built into the calculation of deadly dose for humans. A common standard used to describe the toxicity of a substance is an LD50. An LD50 is the Lethal Dose required to kill 50% of a population of rats. It is not used as a level of safety for humans, but merely as a measure to compare the toxicity of different substances. The following figures compare the toxicity of pesticides to three substances commonly consumed by humans: caffeine, aspirin and common table salt which in high doses can be fatal. When looking at LD50 comparisons, keep in mind that the higher the number, the safer the product. Note that caffeine, which is present in tea, coffee and cola soft drinks, is more toxic that many pesticides. Just because something has a high LD50 (it is not very toxic) does not mean that precautions should not be taken. Whenever pesticides are used, protective clothing should be worn, and the label instructions read carefully and heeded.        Benefits/Problems Pesticides have dramatically increased plant yields, which means that food is cheaper and less workers are required to grow the same amount of food. There are problems arising because pests are becoming resistant to pesticides, which means the pesticide does not kill them. Overcoming pest resistance is one of the big challenges facing food production and habitat conservation. Consumers are demanding that food is produced using less and less chemicals (such as pesticides), because they believe chemicals may be dangerous to their health. Pesticides are used for pest control because        1.pest control is acheived very quickly       2. they are simple to use       3. they are inexpensive in the short-term       4. they have less impact on the environment compared to           other pest control strategies (eg cultivating weeds           destroys thestructure of the soil).       5. the level of pest control acheived is often very high Pesticides are not always used because       1.pests develop resistance to the pesticide       2. they kill too many non-pest organisms       3. they are too expensive       4. there are other,cheaper methods available to control pests Go to the Careers Section to meet some people who are looking at how chemicals are used in pest