Introduction

Classes and uses of pesticides

Legal framework

Approval Levels

Scientific information in the regulatory process.

Risk Management Process

Constitution and function of the various organisations

Management of pesticides in the future.

Exposures to Operators, other workers and bystanders....

The other circumstance in which human exposure to pesticides commonly occurs is in the course of their application or through contact with crops or other materials that have been treated with them. For example, an operator might be exposed when mixing or applying a pesticide; a passer-by or neighbour might be exposed inadvertently to droplets that drift when a pesticide is being sprayed; and a worker harvesting a crop that has been treated might handle foliage that is coated with residues of a pesticide. Most often, the uptake of pesticides from such sources will be by absorption through the skin (dermal absorption), but exposure by inhalation is also possible when products are sprayed or the active substance vaporises.

Estimating the profile of exposure in operators, other workers and bystanders is complex and must take into account many factors. These include:

• the physical form of the pesticide (e.g. liquid or granules);

• the way in which it is used (e.g. sprayed with a tractor mounted sprayer or painted with a brush);

• the circumstances in which exposure occurs (e.g. during mixing and application or through contact with a treated surface);

• the use of any personal protective equipment such as gloves or a face mask;

• the extent to which the pesticide penetrates the skin;

• patterns of use (including frequency and duration).

Sometimes it is necessary to carry out experiments to establish the likely extent of exposures. Often, however, a first step is to estimate the exposure by use of a mathematical model. Models have been constructed for various exposure scenarios such as the tractor-mounted spraying of cereal crops and the application of pesticidal surface coatings by brush. The models are based on representative measurements, and tend to err on the side of over-estimating exposures. For example, in the absence of data to the contrary, they assume that a relatively high proportion of the pesticide is absorbed when it is in contact with the skin.

Once an exposure has been estimated, it is compared with the acceptable operator exposure level (AOEL) (although the term AOEL makes specific reference to operators, it is usually also an appropriate comparator for other workers and bystanders/neighbours), or with the NOAELs from relevant toxicity studies. If the AOEL is not exceeded or the ratio of NOAELs to the estimated exposure is sufficiently high, the exposure is considered acceptable. Where the exposure, when estimated by a model, is greater than the AOEL, it may be possible to refine the calculation through use of additional experimental data. For example, experimental assessment of skin absorption might show that it is lower than the relatively high rate assumed by the model. However, the use of a new product cannot be approved until exposure is shown to be acceptable.

Sometimes, acceptable operator exposure can only be achieved through the use of personal protective equipment such as gloves, coveralls and face-masks. This may be satisfactory for professional operators but amateurs cannot always be expected to have the knowledge that is required to select and use the appropriate forms of protective equipment. Therefore amateur uses of pesticides are not generally approved where exposures would be acceptable only with the use of specialised personal protective equipment. It is important to note, however, that exposure can be controlled by means other than protective clothing; for example, us of suitable packaging for products can reduce the exposure of users.