Letters Metals in Environmental Systems Sir: In "Metals in Bioenvironmental Systems" [ANAL. CHEM., 49 (14), 1210A-14A (Dec. 1977)], Morgan and Bretthauer describe very well the various environmental pathways toxic pollutants may take, and the analytical problems associated with monitoring them. However, I believe they tried (or were required) to cover too much territory. For they have made some statements I doubt they would repeat if they examined them critically. An example is their statement that information relating to the pathways of trace metals in a critical receptor ". . . can indicate the dose of the pollutant to the receptor and also indicate some of the changes in biochemical functions that may take place. For many toxic trace metals the blood level is presently the most important factor in determining effects." Changes in biochemical functions :annot be detected by measuring either dose or concentration without
consideration of the normal function. Further, the accumulation of material in tissue is not necessarily pathological. It may be the measure of the effectiveness of a normal mechanism for rendering toxic materials tolerable or harmless. The presence of a material in the blood is no measure of the effect of that material on the physiology any more than Jimmy Carter's having been elected President affected the severity of the winter of 1977-78. Later, they state, "As has been identified many times, the weakest link in pollution health effects is inadequate knowledge of individual exposure." It sounds right, but is it? Isn't it really the lack of knowledge of whether there is health effect at a given exposure? If two people receive identical doses of the same material, and it has no effect on one but incapacitates the other, is this an indication of pathological contamination or perhaps an allergy or weakness inherent in one person's physiology? The truth of the matter is, we do not know the "background" levels of "toxic" metals. What was the ideal level of iron in the blood before Geritol? (Before Hadacol?) What concentration levels were involved in our evolution, and what would happen if we were able to reduce the ambient levels of these to a level below that?
The authors appear to assume that if a "toxic" heavy metal can be detected in body fluid, it must therefore be evidence of pathology. I cannot accept this. They appear to have no faith in the human organism's ability to fend off harmful materials without the help of the EPA. The many efforts being made to devise more sensitive test methods is no doubt laudable and intellectually satisfying, but I do not believe the threshold of detectability should be equated with the toxicity threshold until we know a great deal more about the ability of biological systems to tolerate or reject foreign materials. Clifford G. Shultz National Laboratories, Inc. 600 Bond St. Evansville, Ind. 47708 Reply: We appreciate the opportunity to respond to Dr. Shultz' excellent comments on our article. We realize there is general agreement that high levels of air pollution or environmental pollution can shorten human life. However, there is substantially less agreement on the fact that low levels of environmental pollutants have definite or significant effects on human health. Biological variability has long been recognized and taken into ac-
NEW CONCEPTS S Y M P O S I U M A N D W O R K S H O P ON DETECTION AND IDENTIFICATION OF EXPLOSIVES A symposium /workshop to s o l i c i t n e w a n d i m a g i n a t i v e a p p r o a c h e s for the detection and identification of illegally used explosives is being sponsored by the U.S. Departments of Treasury, Energy, Justice and Transportation on October 30, 31 and November 1, 1978 in Reston, Virginia. The purpose of this symposium is to desseminate to a broad range of currently uninvolved members of the scientific and technical community: 1) current needs and problems 2) state of current research and 3) interest of the federal sector in new ideas and approaches. General and poster sessions will be used to describe operational requirements and the state of current technology. Small workshop sessions will be utilized to explore new approaches. Registration will be held on October 29 between 6 PM and 8 PM.
Examples of current research which will be discussed include: Vapor Detection Method· Natural vapor characterization Vapor tagging of explosives Detection instrumentation Animals Non-Vapor Detection Methods Nonionizing; e.g., NMR, FIR Ionizing; e.g., X/"yray, CT Deactivation of Blasting Caps Non-Vapor Taggants Identification Methods Identification Taggants Debris Analysis Taggant Incorporation Methods Microencapsulation Vapor Absorption Coatings /Alloying
CIRCLE 3 O N READER SERVICE CARD 626 A ·
A N A L Y T I C A L CHEMISTRY, V O L . 5 0 , NO. 7, JUNE
1978
Limited funds may be available to encourage the participation of a few researchers. Applications for travel support are currently available and must be returned to the Symposium Chairman by 1 August 1978. Researchers are also encouraged to submit papers and poster session displays. A short outline of proposed papers or displays should be submitted to the Symposium Chairman by July 17, 1978. Anyone interested in attending, presenting papers or displays, or otherwise participating in this symposium should contact: A. Atley Peterson, Symposium Chairman, Bureau of Alcohol, Tobacco and Firearms, 1200 Pennsylvania Ave., N.W., Washington, D.C. 20226 (202) 566-7436.
