Organic food proponents express concern over the potential negative effects of various chemical cultivation methods and genetic modification techniques used in modern conventional agriculture. The effect of pesticide residues from crop spraying, the presence of veterinary drugs in meat products, and the relatively unknown long term impacts of genetically modified varieties and breeds are all encompassed. Organic food is seen as avoiding relieving these concerns by prohibiting such practices. At present, there are no definitive scientific conclusions on any of these matters; individual studies are cited on both sides of the debate. Organic food proponents cite the existence of reduced levels of pesticides and herbicides as a way to reduce the long term risk of chemical consumption. The degree of risk posed by pesticide residues remains uncertain. Pesticide use in conventional food products is heavily regulated, with established, research-based maximum residue levels (MRLs) below which residues are considered safe for human consumption. Also, many pesticides are not cumulative in the body, and are regularly eliminated. Notable exceptions include heavy metals such as lead or mercury which are sometimes found in foodstuffs in countries which have lax food production standards. This encyclopaedia will develop in the student an understanding of the principles of this subject. In order to make the subject simple and interesting every topic included in this book has been self-sufficient in itself and has been explained in the light of modern development in a simple and elegant style.