Lead, toxicity, pollution

Deputy Surgeon General L. H. Gehrig spoke frankly Some maintain that a large segment of the population is already perilously close to the threshold of lead toxicity as a result of environmental exposure others take an almost diametrically opposed position. He also conceded that across the entire range of environmental health problems, we are making a rather belated start. Until the conference, the USPHS had focused on hydrocarbons and sulfur dioxide and rarely referred to tetraethyl lead as a pollution problem. 

Concentrations of Toxic Pollutants in the Raw Wastewater of the Primary Lead Subcategory... 

Wastewater is generated in the primary zinc and primary cadmium recovery subcategories by acid plant blowdown, which results from sulfuric acid recovery, air pollution control, leaching, anode/ cathode washing, and contact cooling. The streams may contain significant concentrations of lead, arsenic, cadmium, and zinc. Tables 3.26 and 3.27 present classical and toxic pollutant data for the primary zinc and primary cadmium subcategories. 

Many toxic pollutants were detected in the process wastewaters from metal molding and casting processes. The toxic pollutants detected most frequently in concentrations at or above 0.1 mg/L were phenolic compounds and heavy metals. The pollutants include 2,4,6-trichlorophenol, 2,4-dimethyl-phenol, phenol, 2-ethylhexyl, cadmium, chromium, copper, lead, nickel, and zinc. Each type of operation in the foundry industry can produce different types of pollutants in the wastewater stream. Also, because each subcategory operation often involves different processes, pollutant concentrations per casting metals may vary. 

Slimicide and biocide toxic pollutants containing pentachlorophenol are used at mills in the pulp, paper, and paperboard industry. Initially, pentachlorophenol was used as a replacement for heavy metal salts, particularly mercuric types. Trichlorophenols are also used because of their availability as a byproduct from the manufacture of certain herbicides. Formulations containing organo-bromides and organo-sulfur compounds are also being used. Substitution of alternative slimicide and biocide formulations can lead to the virtual elimination of pentachlorophenol and trichlorophenol from these sources. 

In addition to the conventional pollutant constituents, USEPA made a survey of the presence of the 126 toxic pollutants listed as priority pollutants in refinery operations in 1977 [5]. The survey responses indicated that 71 toxic pollutants were purchased as raw or intermediate materials 19 of these were purchased by single refineries. At least 10% of aU refineries purchase the following toxic pollutants benzene, carbon tetrachloride, 1,1,1-trichloroethane, phenol, toluene, zinc and its compounds, chromium and its compounds, copper and its compounds, and lead and its compounds. Zinc and chromium are purchased by 28% of all refineries, and lead is purchased by nearly 48% of all plants. 

Toxic pollutants resulting from production processes within this industry are generally the result of leaks, spills, and poor housekeeping procedures. Pollutants include organics associated with the raw materials and lead from the rubber curing process. 

C. Because they were used in gasoline to boost octane rating, alkyl lead compounds found their way into the environment as toxic pollutants. One way to measure lead compounds in natural waters is by anodic stripping voltammetry (Figure 17-20), in which the lead is first reduced to the element at a mercury electrode and dissolves in the mercury. Reoxidation occurs when the electrode potential is made sufficiently positive, with current proportional to the concentration of dissolved Pb. 

Recycling of certain household waste, such as televisions, computers, and rechargeable batteries, is desirable to control toxic pollution. Televisions are a significant source of lead that can leach into groundwater from dump sites. 

Emission studies show that lead is only a small part of the automotive pollution problem. Prior to control, hydrocarbon emissions were more than 40 times and the oxides of nitrogen emissions more than 15 times the emission of the lead compounds. Obviously, however, legislation will result in the eventual elimination of lead from gasoline. The removal of lead, besides eliminating a possible toxic pollutant, simplifies the problem of handling other automotive exhaust pollutants in that catalytic exhaust chambers perform much better in the absence of lead contaminant. All emission standards become particularly severe in 1975 and 1980. The particulate standards are equivalent to 1 gram Pb/gal in 1975 and 0.3 gram Pb/gal in 1980. Since the particulates include all solid materials, tolerable lead levels will be less than indicated above. 

The batteries of principal concern at this time are lead-acid batteries, nickel-cadmium batteries, and mercury batteries. Even though they may contribute smaller amounts of toxic pollutants to MSW than other sources, concerted efforts are and should be made to prevent pollutants from these batteries from entering the foodchain and from becoming a health hazard. 

Mercury and arsenic are extremely toxic heavy metal and metalloid pollutants that adversely affect file health of millions of people worldwide (/). These toxic pollutants have reached unacceptably high levels in file environment due to industrial, def e, agricultural, and municipal properties. The U.S. Department of Energy (DOE) and other government and industrial sites in the United States are heavily contaminated with mercury, arsenic, and other toxic metals such as cadmium, copper, lead, and zinc. Each of these elemental pollutants has common environmentally relevant electrochemical species that are thiol-reactive and thus relevant to the phytoremediation strategies oufiined in Figure 1. Hundreds of Superfimd sites in the United States are listed on file... 

It is evident that concern for the effects of environmental lead pollution is well considered, and it is essential for the medical and scientific communities to study further the problem of low lead toxicity and its effects. 

This book is organized into five coherent and interactively related parts containing a total of 29 chapters. Each of the five parts, in turn, is subdivided into chapters that are sequenced to develop topics and their rationales and their contributions to the overall purposes of both the part and the entire book. Parts 1—3 address the science of lead as a pollutant in the human environment and as a potent human toxicant. Part 1 presents multiple chapters on lead in the human environment. Part 2 deals with relevant aspects of defining human lead exposures. Part 3 presents an examination of the nature and extent of human lead toxicity in subsets of the population using criteria for importance and for reliable data availability to inform evaluations done on a body system or organ/organ grouping basis. 

The epidemiology of the effects of environmental disasters has also emerged as a powerful means of assessment of the effects of toxic metals in the human organism, especially of mercury. The epidemiology of lead toxicity has also been of value in understanding the limits of safety of this serious environmental pollutant. 

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