Introduction

Some persistence is a desirable characteristic of useful chemical products, since otherwise the chemical would degrade instantaneously into inert components of little usefulness. The objective of any purchaser of a chemical product is to acquire the activity of the product. The more persistent the product, the less often the purchaser must expend the labour and capital required to apply it. For these reasons chemical persistence is not an unmitigated ‘bad’; it is in fact an in-built characteristic driven by the demands of consumer groups.

However, the socially optimal degree of persistence is not necessarily ensured through market mechanisms, since persistence redounds to the benefit or detriment of many individuals other than the purchaser. Specifically, since chemicals that are persistent must be active within one of the various basic environmental media (atmospheric, hydrological or organic), this activity will also be experienced by the many others in contact with the same medium. Since this activity may be undesirable from the perspective of the many other persons subjected to it, they might prefer a lower level of persistence than would the individual who is making the purchase decision without taking their preferences into account. It is the internalisation of this externality that is the subject of this chapter. Policies must be designed in order to mitigate the problem of greater-than-optimal product durability when persistence ensures that people other than the consumer will feel the impacts of the product. The particular policies that we investigate here are those that will cause manufacturers and users to take the correct decisions in the design and application of agricultural pesticides.