Sources of Lead in the Environment

The primary source of lead in the environment has historically been anthropogenic emissions to the atmosphere. In 1984, combustion of leaded gasoline was responsible for approximately 90% of all anthropogenic lead emissions. EPA phased out the use of lead alkyls in gasoline, however, and by 1990, auto emissions accounted for only 33% of the annual lead emissions (EPA 1996h). Use of lead additives in motor fuels was totally banned after December 31, 1995 (EPA 1996f). The ban went into effect on February 2, 1996. Atmospheric deposition is the largest source of lead found in soils. Lead is transferred... 

SOURCES OF LEAD IN THE ENVIRONMENT 1.2.1. General Sources of Lead... 

Berlin, E. P. 1970. Principles and Practice of X-Ray Spectrometric Analysis. Plenum, New Yorif. Billick, 1. H. 1983. Sources of lead in the environment. In Lead Versus Health (M. Rutter and R. Jones, eds.). Wiley-Interscience, New York. 

Humans have been exposed more and more to metallic contaminants in the environment, mostly from the products of industry. There are three main sources of metals in the environment. The most obvious are the processes of extraction and purification mining, smelting, and refining. Another is the release of metals from fossil fuels (e.g., coal, oil), when these are burned. Cadmium, lead, mercury, nickel, vanadium, chromium, and copper are all present in these fuels, and considerable amounts enter the air or are deposited in ash. The third and most diverse source is the production and use of industrial products containing metals, which is increasing as new applications are found. The modem chemical industry, for example, uses many metals or metal compounds as catalysts metal compounds are used as stabilizers in the production of many plastics, and metals are added to lubricants, which then find their way into the environment.21... 

In addition to hydroxy-PCDEs, nitro- and aminoderivatives of PCDEs could be possible sources of PCDEs in the environment. Nitrofen is prepared by base-catalyzed condensation of 2,4-dichlorophenol (2,4-DCP) with l-chloro-4-nitrobenzene [30]. PCDEs have not been detected in 2,4-DCP and 2,4,5-TCP [37] but, in theory, just as the occurrence of PCDE by-products in chlorophe-nols is most likely due to the condensation of chlorophenols, the condensation of 2,4-dichlorophenol during the manufacture of nitrofen might lead to the formation of PCDEs. Aminofen is produced from nitrofen by catalytic reduction [4],... 

There are various sources of radiocesium in the environment. The input from atmospheric weapons testing in the mid-twentieth century leads to the most widespread and homogeneous contamination of soil and water. The accumulated contribution of Cs in Europe from this source is estimated to be about 1000 Bq m 2. The fairly uniform deposition of Cs from fallout followuig the nuclear weapons testing has led to the widespread use of this isotope as a tracer of erosion (Ritchie and McHenry, 1990 Agudo, 1998). The accident that occurred at the Chernobyl nuclear plant in April 1986 led to more localized contamination. The events that led to this accident and the consequences have been widely... 

For a brief discussion of dust from occupational exposure as a source of lead in the home environment, see Chapter 2. 

Evidence for the existence of a natural source of tetraalkyllead compounds comes from analysis of air from the open sea, from coastal, and from estuarine areas, since 1 to 30 ng/m tetraalkyllead was observed [61] further evidence was found from abnormally high alkyllead to total lead ratios, which have been observed in atmospheric samples in Morecambe Bay, U.K. [60]. It was speculated that these tetraalkyllead emissions arise from methylation of lead compounds in coastal and estuarine intertidal areas [61]. The hypothesis of a natural source was supported by additional measurements [132, 174] see also [46, 133, 134]. However, according to recent results on transformation rates and lifetime of alkyllead species in the atmosphere it is not necessary to invoke the hypothesis of the natural alkylation of lead to explain the enhanced alkyllead to total lead ratios [182]. Also no indication of a large-scale natural source for tetraalkyllead compounds was found in other work [22], and determination of atmospheric content of tetraalkyllead compounds gave no indication for the occurrence of natural methylation processes of lead(ll) compounds [23] see also [48, 69, 70, 73]. The origin of trialkyllead species in rural pigeons (Columba livia) was associated in part with natural sources of tetraalkyllead in the environment [135], and also the presence of small amounts of Pb(CH3)4 in fish (Coho Salmon, Yellow Perch, Sucker, Rock Bass, Sunfish) from various lakes and rivers in Ontario, Canada, was taken as an indication for the possibility of environmental methylation or in vivo methylation of lead in fish [95] see also [93]. It was considered conceivable that bacteria in fish intestines or in fish tissue could methylate lead compounds [93, 94, 101, 178]. 

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