Report
Ultratrace Metals in Some Environmental and Biological Systems Joseph J. Dulka Terence H. Risby Department of Chemistry The Pennsylvania State University University Park, Pa. 16802
Current opinions suggest that minute quantities of metals are required for most biological systems to survive. Often it is impossible to use normalsized samples for trace analysis; therefore, the investigation of microsamples requires ultratrace techniques. For this discussion, ultratrace is defined as less than 1 part per million or as less than 1 microgram. Analysis of ultratrace quantities of toxic metals accumulated in biological systems requires precision microsampling techniques which are presented in this study. The areas investigated are environmental, pertaining to airborne samples, and biological samples from human and bacterial systems. In environmental systems, samples containing toxic metals and metals used to fingerprint emitting sources are discussed. In biological systems, samples containing toxic, essential, and undefined metals are studied. Environmental Systems Trace Metals. All forms of the ecological system are affected to varying extents by metals. Metals are the most insidious pollutants because of their nonbiodegradable nature. As shown in Table I, only a few metals are completely nontoxic at any level. Even these metals could be harmful if they unbalance or displace the essential metal levels in the ecosystem. Some metals are highly active, either undergoing chemical reaction them-
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selves, or serving as catalysts for the reaction of others (1). Metals in the environment are from natural and "man-made" sources. The main point which should be drawn from Table II is that natural pollution accounts for 82% of the total emission (natural dusts and forest fires). Ultratrace levels of metals in the soil or water can result in the accumu lation of these metals by both flora and fauna through their various food chains. Therefore, the effects of ultratrace levels of metals on human health are often very subtle. Symptoms of poor health caused by metals are often improperly diagnosed. Particulates and gases generally enter the body through the respiratory system, while certain liquids and gases may be absorbed through the skin. Particles greater than 1 μπι are usually trapped and removed by the body's respiratory filters. Smaller particles can pass deep into the lungs and re main there. Because particles can act as vehicles for the transport of gaseous pollutants, the possibility for harmful synergistic effects exists. Recent investigations (3, 4) have demonstrated that certain toxic met als are preferentially concentrated in submicrometer-sized particles. For
metals to be efficiently absorbed into any biological system, they must be contained in particles smaller than 1 μτη and must be solubilized by some natural biochemical process. Since present particulate emission control systems generally fail to collect submi crometer-sized particles, regulatory agencies are failing to control the most harmful materials. These materials may cause short-term irritant effects or longer-term damage such as silico sis, chronic bronchitis, emphysema, and other respiratory illnesses. Cur rently, only beryllium and mercury emissions are regulated by Federal Emission Standards. Other federal regulations concerned with particulate material emission establish an upper limit of 75 μg/τn3 for the annual aver age and 260 Mg/m3 for any given 24-h period. Table III shows the annual metallic emissions from stationary and mobile sources during 1970. Some of the inhaled matter is re moved from the lungs and bronchial passages by mucociliary action and transported to the gastrointestinal system where they may exert a direct toxic effect or may be absorbed and transferred to other areas and tissues. However, the absorption efficiency of metals by most alimentary canals of
Oxidation states of trace metals, synergistic effects of metals on the toxicity of other compounds, and long-range effects of ultratrace metals require seri ous study
