Lead, human toxicity measurement

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. 

Effect of Dose and Duration of Exposure on Toxicity. No studies were located where -hexane concentration was measured in workplace air before workers became ill, so no dose-response relationship can be defined for human neurotoxicity as the result of -hexane exposure. Information on duration of exposure leading to toxicity is available from some case series reports. An occupational exposure caused sensory disturbances in the lower extremities after approximately 2 months (Herskowitz et al. 1971). A case of peripheral neuropathy after 7 months of exposure was reported among press-proofing workers in Taipei (Wang et al. 1986) a serious case resulting in quadriplegia after 8 months of exposure was reported among sandal workers in Japan (Yamamura 1969). Based on case reports, it can be estimated... 

So what is known abont lead It is one of the few elements which seem to have no biological function, and its water soluble compounds are mostly toxic. In the human body, it accnmnlates in the bones as insoluble phosphates. Today s human bones contain about double the amount of lead that was measured in Stone Age skeletons, yet today s values are several times lower than it was in the bones of people who lived in the last two millennia. The health effects of lead remained im-known for a surprisingly long time in hrnnan history. 

During PO processing at elevated temperatures, highly volatile additives may contaminate the atmosphere vapors or gases may lead to toxic effects for humans, but appropriate protection measures (local exhaust devices) can prevent this. 

A second approach to the problem of toxic potency measurement has been to expose laboratory animals, usually rodents, to the smoke from the combustion of small samples of a burning material. Measurement of their response to the smoke leads to one of several biological endpoints, such as the LC50 (the concentration of smoke lethal to 50% of the test animals). In this approach, the animals respond to all the toxicants that are present in the smoke. It presumes that rodent mortality can be related to human mortality or, more simplistically, that the relative toxicity of the smokes will be similar in humans and rodents. However, since the relative contributions of the individual toxic chemicals in the smoke are not determined, a quantitative relationship between man and rodent is impossible using this approach. 

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. 

The wearing of copper bracelets to benefit arthritis is an apocryphal use of copper. It is not clear whether any measurable amount of copper is dissolved by the body. The average weight loss from copper bracelets is 12 mg month-1 while they are worn. Studies show that components in human sweat could solubilize this metal and possibly aid its absorption. On the other hand, copper-coated intrauterine devices can lead to the dissolution of about 25-50 mg Cu per year. There are no studies to show whether this leads to chronic copper toxicity or whether there is a protective effect against... 

Public concern for the hazards of particle suspensions in the indoor and outdoor environment has produced regulations limiting particle concentrations and exposure levels. In the workplace, dust hazards are constrained by total mass concentration as well as concentration of specific toxic chemicals. In the ambient air, protection is stipulated in terms of total mass concentration of suspended particles andcertain chemical species, namely, lead and sulfate. Recently, measures of exposure have begun to distinguish between fine particles less than 2.5 fxm and coarse particles between 2.5 and 10 fxm. This separation relates to the ability of particles to penetrate the human respiratory system, and to different sources of fine and coarse particles. 

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