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- 19 - distributed in the biosphere; hence, they are generally found at low levels in crops and soils. Application of pesticides containing any of these elements augments the natural level. Metallic pesticidal chemicals are highly toxic and are excreted slowly from the body. They were used in the inorganic form in the past, but the current practice is to use organic compounds of these metals. The organic compounds are less toxic on a single-dose basis, but the body metabolizes them to their inorganic form. Precautions concerning degree of exposure and accumulation in the body are the same for the organic derivatives as for the corre- sponding inorganic compounds. The use of many of the metallic pesticides is on the wane. However, the increasing use of organic arsenical herbicides presents a growing arsenic-contamination problem. MONITORING RES !DUES IN THE ENVIRONMENT The 1963 report of the President's Science Advisory Committee recommended that "current pesticide levels and their trends in man and his environment" be determined and that "a continuing network to monitor residue levels in air, water, soil, man, wildlife, and fish" be developed. In response to these recommendations, several federal agencies set up the National Pesticide Monitoring Program (NPMP), following guidelines provided by the Federal . com- mittee on Pest Control, an interagency body. The agencies that set up NPMP were already engaged in monitoring activi- ties, and they continue to administer the activities that are now identified with NPMP. Some NPMP activities were instituted after NPMP was formed. In June 1967 the Federal Committee on Pest Control began publishing the Pesticides Monitoring Journal, the purpose of which is to report results of monitoring inves- tigations--both those conducted by agencies associated
- 20 - with NPMP and those conducted by other agencies. In the first issue, the Journal defined pesticide monitoring as the determination of "the distribution of pesticides in the various elements of the environment and the changes in these levels with time." As NPMP is now conducted, however, the emphasis is on measuring changes in the concentrations of pesticides in selected components of the environment. Those parts of NPMP that follow pesticides in people are designed to measure changes that occur in selected communities or in tissues obtained from designated hospi- tals. In contrast, programs related to food emphasize careful objective sampling to determine the average content of a standard diet. Enough dietary components are analyzed separately to permit calculation of residue content for a number of basic diets. In addition, raw produce and meat are randomly sampled. Thus, for food, the program provides not only for measuring changes but also for calculating meaningful average values. These studies of man and his food have, of course, been set up for good public-health reasons, and statements of objectives are outstandingly clear. If any increase in residues is noted in the samples of man or his food, cor- rective action generally is taken promptly. However, these studies do not provide data needed for assessing the presence of pesticides in natural environments. The program for monitoring soils is based on selected sampling of forest, range, and agricultural lands. Most samples of agricultural soils are taken from farms where the history of pesticide use is known. More extensive sampling according to a well-established sampling design is required to provide information on the accumulation of residues in the total soil mass. A plan for expanding soil monitoring to include more general sampling on a statistical basis is being developed. Pesticides in water are monitored by sampling rivers at selected sites. Changes at these sites are measured, but information on average conditions is lacking. Related samplings are those of shellfish in estuaries, the surface of estuarine sediments, freshwater fish (three species)
- 21 - taken at a number of points on rivers, and birds (three species). Like the river samplings, these studies are concerned with selected parts of the ecosystem and measure changes; they are not capable of determining the distri- bution or extent of residues in the various parts of the ecosystem. Thus, it is seen that the National Pesticide Monitor- ing Program has two groups of studies and that they differ markedly in their objectives: --The measurement of residues in human tissues and in food is designed to follow pesticides in man and his food, not to reflect residues in the general environment. --The sampling of water, shellfish, estuarine sedi- ments, freshwater fish, birds, and (to some extent) soil is designed to furnish index values for measuring changes in the amounts of residue in selected components of the biosphere. The air-sampling program of NPMP, which is only beginning, should be expanded. Although the technology of air sampling is not well advanced, air sampling must be included in any effort whose aim is to monitor the health-related aspects of man's immediate environment. Further, the absence of quantitative information about transport of pesticides in the atmosphere is a critical deficiency in our understanding of the biosphere circu- lation of the persistent materials. The Committee believes that an air-sampling network should be established. Pri- mary attention should be given to man's immediate environ- ment, but the network should also monitor the environment generally. The Committee believes that monitoring programs should include determinations of the concentrations and amounts of pesticide chemicals in the major reservoirs of the biosphere and assessments of the changes in con- centration with time. Such information would permit esti- mation of the amount and rate of change of residues in the biosphere.
