Lead contamination

Soil. The first reported field trial of the use of hyperaccumulating plants to remove metals from a soil contaminated by sludge appHcations has been reported (103). The results were positive, but the rates of metal uptake suggest a time scale of decades for complete cleanup. Trials with higher biomass plants, such as B.juncea, are underway at several chromium and lead contaminated sites (88), but data are not yet available. 

Lea.dAnodes. A principal use for lead—calcium—tin alloys is lead anodes for electrowinning. The lead—calcium anodes form a hard, adherent lead dioxide layer during use, resist corrosion, and gready reduce lead contamination of the cathode. Anodes produced from cast lead—calcium (0.03—0.09 wt %) alloys have a tendency to warp owing to low mechanical strength and casting defects. 

Silver reduces the oxygen evolution potential at the anode, which reduces the rate of corrosion and decreases lead contamination of the cathode. Lead—antimony—silver alloy anodes are used for the production of thin copper foil for use in electronics. Lead—silver (2 wt %), lead—silver (1 wt %)—tin (1 wt %), and lead—antimony (6 wt %)—silver (1—2 wt %) alloys ate used as anodes in cathodic protection of steel pipes and stmctures in fresh, brackish, or seawater. The lead dioxide layer is not only conductive, but also resists decomposition in chloride environments. Silver-free alloys rapidly become passivated and scale badly in seawater. Silver is also added to the positive grids of lead—acid batteries in small amounts (0.005—0.05 wt %) to reduce the rate of corrosion. 

In electrogalvanizing, copper foil, and other oxygen-evolving appHcations, the greatest environmental contribution has been the elimination of lead-contaminated waste streams through replacement of the lead anode. In addition, the dimensionally stable characteristic of the metal anode iatroduces greater consistency and simplification of the process, thus creating a measure of predictabiUty, and a resultant iacreased level of safety. 

The Occupational Safety and Health Administration (OSHA) regulates the exposure to chemicals ia the workplace. From the poiat of view of the inorganic pigments iadustry, the limits estabUshed for lead and cadmium exposure are particularly important. A comprehensive lead standard adopted by OSHA ia 1978 has been successful ia reduciag the potential for lead contamination ia the workplace. 

Air. Studies have shown that 2500 years ago lead pollution caused by Greek and Roman silver smelters was a significant problem (4). Based on analysis of lake sediments and Greenland s ice, it was found that lead contamination from smelters in southern and central Europe was carried throughout the northern hemisphere. As long ago as the thirteenth century, air pollution has been linked to the burning of coal (4). The main concern was the smell from the sulfur in the coal and the effects of the soot. It was not until many years later that the effects of air pollution on people s health were discovered. 

Oxygen evolved from the anodes as well as some hydrogen from the cathodes produces a mist which is trapped by a froth maintained by adding cresyhc acid, sodium siUcate, and gum arabic, or glue plus cresol. Alkaline-earth carbonates prevent lead contamination of the cathode ziac. Most of the lead is deposited ia the cell sludge as iasoluble carbonate—sulfate. 

Capodaglio, G., Scarponi, G., P. Cescon. Lead contamination of seawaters with different anthropic influence. Ill International Conference "Environmental Contamination", Venice, Sept. 1988, pp. 505-407. 

Using Geostatistics in Assessing Lead Contamination Near Smelters... 

Roberts TM, Hutchinson TC, Paciga J, Chattopadhyay A, Jervis RE, VanLoon J, Parkinson DK. 1974. Lead contamination around secondary smelters estimation of dispersal and accumulation by humans. Science 186 1120-1123. 

In preparation for one trip, Patterson and his colleagues cleaned 500 plastic containers in vats of nitric acid, rinsed them in pure water, filled them with pure argon to displace lead-contaminated air, and sealed them in plastic bags equipped with breath filters. Even then, the containers contributed about 0.05 millionths of a gram of lead to each sample as they were trucked from the factory to Caltech, automobile exhaust had sprayed them with thousands of micrograms of lead. For Patterson s next trip, he collected the containers directly from the factory production line and sealed them immediately into plastic bags before their trip to his laboratory. 

Environmental Lead Contamination in December of 1965. More than half of its 32 participants represented the lead industry or federal health and research groups from Ohio and Michigan, strongholds of the automobile industry near Kehoe s laboratory. Attendees abandoned any pretense at neutrality and let their emotions and biases bubble over. Perhaps it s because the trigger, Dr. Patterson s article, is so obviously an emotional article, an observer commented. 

U.S. Public Health Service. Symposium on Environmental Lead Contamination. Dec. 13-15, 1965. U.S. Department of Health, Education, and Welfare. FS2.2 646/4. 

The risk assessment has also concluded that a level of 200 mg/kg for lead in the soil will be a protective level for expected site exposures along with an excess cancer risk level for TCE-contaminated soil (56 pg/L). Based on investigations of activities at the site, the TCE-contaminated soil has not been determined to be a listed RCRA hazardous waste, as the cleaning solution records indicate the solution contained less than 10% TCE. However, the lead-contaminated soil is an RCRA hazardous waste by characteristic in this instance due to extraction procedure (EP) toxicity. None of the waste is believed to have been disposed at the site after November 19, 1980 (the effective date for most of the RCRA treatment, storage, and disposal requirements). 

For the site remediation case shown in Figure 16.21, this alternative consists of in situ SVE of TCE-contaminated soil (Area 2), in situ soil fixation of lead-contaminated soil (Area 1), cap (Area 1), and the groundwater pump-and-treat components of Alternative 3. 

This alternative includes components of Alternatives 3 and 4 and introduces a thermal destruction component to address the TCE-contaminated soil. For the site remediation case shown in Figure 16.21, the lead-contaminated soil in Area 1 would be fixed and covered with a soil/clay cap, as described in Alternative 4. The groundwater would be addressed through pumping and treating, via an air stripper, as described in Alternatives 3 and 4. The TCE-contaminated soil in Area 2 would be excavated and treated on site by a thermal destruction unit comprisng a mobilized rotary kiln. 

The facility would use a dry scrubber system for emission control, which would eliminate the need for wastewater treatment. Any water from emission control and from decontamination procedures would be treated in the on-site groundwater treatment system. The residual soil and collected ash is assumed to be nonhazardous and can be disposed of in a solid waste disposal facility in compliance with subtitle D of RCRA. In the event that they cannot be delisted due to the presence of metals, the residuals will be managed as part of the closure of Area 2 shown in Figure 16.21 (lead-contaminated soil). 

Alternatives 4 and 5 would rely on a soil/clay cap to control infiltration for Area 1 (lead-contaminated) as well as treatment or fixation. Upon completion, some long-term maintenance of the cap and groundwater monitoring would be required until each alternative has met the health-based cleanup goals for groundwater. These alternatives would have almost no long-term reliance on institutional controls. 

Alternative 3 also treats soil and groundwater for TEC. However, ca. 19,114 m3 (25,000 yd3) of lead-contaminated soil would remain untreated on site, although the lead mobility would be very low. 

Existing Information on Health Effects of Lead 5-1 Frequency of NPL Sites with Lead Contamination... 

EPA regulations also limit lead in drinking water to 0.015 milligrams per liter (mg/L). The 1988 Lead Contamination Control Act requires the Consumer Product Safety Commission (CPSC), EPA, and the states to recall or repair water coolers containing lead. This law also requires new coolers to be lead-free. In addition, drinking water in schools must be tested for lead, and the sources of lead in this water must be removed. 

Two intermediate-duration studies in rats in which lead was administered mixed in the food as acetate, oxide, sulfide, and lead contaminated soil identified NOAELS of 5 mg lead/kg/day (Dieter et al. 1993) and 6.4 mg lead/kg/day (Freeman et al. 1996) for food intake for all lead forms tested. These doses were the highest doses tested. A 90-day study in rats reported no effects of lead exposure on water intake in rats administered doses of approximately 38 mg lead/kg/day as acetate via drinking water (Kala and Jadhav 1995a). In contrast, rats given a much higher dose of lead acetate in the water (0.6% corresponding to approximately 502 mg lead/kg/day) for 14-50 days showed a 17-20% decrease in water intake (Ronis et al. 1996). 

People living near hazardous waste sites may be exposed to lead via ingestion of contaminated water or soils or by inhalation of lead particles in the air. For people not living in the vicinity of hazardous waste sites, the major route of exposure to lead is ingestion, particularly of lead-contaminated water, food, soil, lead-based paint chips, or dusts (the latter two are particularly relevant to children in lower-income urbanized populations). For occupationally exposed individuals, the predominant route of exposure is the inhalation of lead particles with oral ingestion also important in many cases. 

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