18.104.22.168. Physical formulation
Generally, the higher the concentration of the AI in the formulation, the finer the required dispersion of the formulation in the field. Target application sites can be treated with the same dose of AI in different ways. For instance, the same dose can be sprayed (one method of product delivery) after final dilution in one hundred litres of water for a tractor-drawn device or in three litres of water or oil (ultra-low volumes) by aeroplane. Depending on the spraying method, the concentrations are not identical and the diameter of the droplets ranges between 1 micron to hundreds of microns. Consequently, the delivery method makes the penetration of the AI into the body of living organisms and its toxicological effects different (Luttrell, 1985). In the same order of size as for droplets (1 to 100 ìm), plastic micro-capsules are conceived to extend the effective life of AI by releasing slowly through pores of the plastic walls (Stoner et al., 1979). Nanoparticles are patented but their biological and environmental fates are poorly documented (Hodgson, 2004).