An increased scale of human activity has brought with it pollution, defined as ‘an undesirable change in the physical, chemical, or biological characteristics of our air, land, and water that may or will harmfully affect human life or that of any other desirable species, or industrial processes, living conditions, or cultural assests; or that may or will waste or deteriorate our raw material resources.’* Under certain circumstances, natural processes are unable to keep pace with the increase of pollutants, and then serious problems arise—usually on a local scale. On occasion, however, pollution effects may persist long enough so that the atmosphere or the ocean circulation may spread them over the whole earth.
It is therefore important to examine the situation at frequent intervals to determine whether a pollutant released in our environment could have far-ranging geophysical effects or far-ranging effects in the biosphere, and to probe particularly all interconnections in order to expose any weak link in the ecological chain. Such an examination should involve scientists from different specialties, including geophysics, geology, biochemistry, biology, medicine, and ecology. The subject matter has obvious interest to the general public, to policymakers in the government and in the Congress, and to all who are concerned about the effects of man's activities on the environment.