Lead, human toxicity measurement techniques

Human toxicity, aquatic toxicity, and the environmental impact of engine coolants and deicing fluids ate typically measured on the fresh fluid only. Spent fluids contain varied contaminants that can drastically affect the toxicity and environmental impact of the fluid. Most pronounced is the impact of heavy-metal contaminants in spent antifreeze. Data on spent and recycled antifreeze, compiled by the ASTM Committee on Engine Coolants, show an average lead level 11 ppm, as weU as various other metal contaminants (iron, copper, zinc) (18). The presence of these contaminants in a used fluid may require special disposal techniques for the fluids. 

For measuring lead in environmental media providing potential human lead exposures, this chapter includes older published data for lead concentrations in media, data which are old enough to encompass the full lifetimes of living populations. This is because of long-term Pb storage in bone. One concern with any appraisal of older lead measurement data in media is that of analytical and statistical data reliability versus that of methods employed with more recent accepted techniques. Sensitivity is of particular concern. A potent toxicant such as environmental lead requires methods for quantification of concentrations of lead at ultra-trace levels in order to permit estimates of the full range of Pb exposures. 

Steps have been taken by the World Health Organization (WHO) and the U.S. Environmental Protection Agency (EPA) to reduce the amount of toxic metal ions in the environment. For example, large concentrations of lead have been shown to be lethal to humans. The maximum amount of lead tolerated in drinking water according to the WHO and the EPA, is 0.05 mg/l(9l) and 0.5 mg/I,(92) respectively. For this reason, innovative techniques to measure low concentrations of metal ions are emerging. 

Consequently, this review is designed to briefly summarize many of the available techniques for accurate measurements of environmental and human lead contamination. This includes the importance of ultraclean techniques for lead analysis as well as brief descriptions of some current and emerging analytical techniques for measuring lead exposures in humans. The descriptions are preceded by abbreviated discussions of the chemical properties of lead, natural and anthropogenic variations in its stable isotopic composition, and historical records of lead contamination in the environment. The report concludes with a summary of some indirect methods of measuring lead exposure and toxicity in humans. Much of the material in this report is based on reviews written for several recent reports Measuring Lead Exposure in Infants, Children, and Other Sensitive Populations (NRC 1993), Lead in the Biosphere Recent Trends (Smith and Flegal 1995), and In Vivo Measurement and Speciation of Nephrotoxic Metals (Smith and McNeill 1995). 

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