es of lettuce and spinach contained nitrate levels exceeding allowed limits.12 From 1,354 t of active ingredients in 1992 to 2,285 t.13 Defined here as the area within the perimeters of the M25 motorway.14 A Californian study indicates that 0.42 ha can meet virtually all individual???s food needs, providing space not just for growing but also for composting and other activities.