Produce or crops that contain above-tolerance pesticide residues or residues of products banned from sales in the United States cannot be sold. Since each and every food item cannot be tested for pesticide residues, subsamples of larger volumes of food are selected. Samples are pulled at random to ensure all have an equal chance of selection for testing. Before testing, food items are prepared for consumption, and subsamples are tested for residue analysis. Risk assessment is how EPA determines tolerances.
Exposure multiplied by the toxicity gives the risk.
The process for evaluating new pesticides must be changed as new technology and safety evaluation procedures are developed. There is an ongoing process to reevaluate the safety of pesticides that were registered before November 1, 1984. More than 1,150 active ingredients have been identified for reregistration. Pesticide manufacturers must evaluate the costs of reregistration versus the potential for sales. Many products presently considered safe will not be reregistered, because the market share is small and the cost of reregistration is great.