Lead paint, bridges

Thomas G. Spiro and William M. Stigliani. Chemistry of the Environment. New Jersey Prentice Hall, 1996. Source for lead-halide particles lead paint on school buses, highways, and bridges. 

According to the 1992 NCHRP data, nearly 80% of the bridges have been coated with lead-based paints. About 4100- 130 million is spent on painting annually. Lead paint removal generates an estimated 181 million kg (200,000 ton) of lead-contaminated abrasives. 

When the City of New York began sandblasting the Williamsburg Bridge in the summer of 1992, neighborhoods on both the Brooklyn and Manhattan sides were showered with toxic lead paint fragments and dust. Yards, sidewalks, and playgrounds were contaminated, so that children could not play outside safely. Residents were irate. 

People exposed to lead in the workplace clearly have the highest exposures overaU, and primary and secondary smelter workers probably have the highest exposures in the occupational category. Certain non-lead production workers also have had high exposures, such as those in the construction and remodeling industries. This includes those who remove old lead paint from bridges and other surfaces. A detailed discussion quantifying such workplace exposures is outside the scope of this chapter, but those workers, ranked in terms of Pb toxicity, are discussed in earher chapters. It is critical to keep in mind that environmental exposures that affect typical risk populations add to workplace exposures. 

Paint. Steel bridges and railings are usucdly painted. Paints that contain lead or zinc are mostly used, because these are especially good at preventing rust. For example, red lead paints contain an oxide of lead, Pb304. 

If the airborne exposure is to be determined for a particular job, the IH must be prepared to monitor quickly. The next day may be too late. Concentrations usually need to be high to find TWAs that exceed OSHA PELs. More often than not the construction worker is not conducting the same job for an 8 h period. Many tasks are usually required to accomplish a day s work, which also makes it difficult to evaluate a particular hazard. A worker welding, cutting, and burning all day on an outside project such as a painted bridge may have no exposure or wind up in the hospital undergoing chelation therapy with a blood lead level in the hundreds. Many variables affect the potential and real exposure levels such as work habits, weather, and type of paint on the steel as well as personal protective equipment used. 

Respiratory Effects. The only information located regarding respiratory effects in humans associated with lead exposure was a case report of a 41-year-old man who was exposed to lead for 6 years while removing old lead-based paint from a bridge. At the time of the initial assessment, his PbB level was 87 pg/dL, and he complained of mild dyspnea for the last 2-3 years. No abnormalities in respiratory function were seen at clinical examination, so it is not possible to conclude that his respiratory symptoms were related to exposure to lead (Pollock and Ibels 1986). 

Cardiovascular effects have been noted in occupationally exposed workers after exposure to high levels of lead following exposure durations of as short as 4 weeks. Construction workers (race not specified) using oxyacetylene torches to cut a metal bridge that had been painted with lead-based paint were reported to exhibit increases in heart rate and blood pressure after 4 weeks of exposure (Marino et al. 

Inhibition of ALAD and stimulation of ALAS result in increased levels of ALA in blood or plasma and in urine. For example, in a case report of a 53-year-old man with an 11-year exposure to lead from removing old lead-based paint from a bridge, a PbB level of 55 pg/dL was associated with elevated urinary ALA (Pollock and Ibels 1986). The results of the Meredith et al. (1978) study on lead workers and controls indicated an exponential relationship between PbB and blood ALA. Numerous studies reported direct correlations between PbB level and log urinary ALA in workers. Some of these studies indicated that correlations can be seen at PbB levels of <40 pg/dL (Lauwerys et al. 1974 Selander and Cramer 1970 Solliway et al. 1996), although the slope may be different (less steep) than at PbB levels of >40 pg/dL. In a study of 98 occupationally exposed subjects (51 pg/dL, mean PbB) and 85 matched controls (20.9 pg/dL. mean PbB) it was found that log ZPP and log ALA in urine correlated well with PbB levels (Gennart et al. 1992a). In the exposed group, the mean ZPP was 4 times higher than in the controls, whereas urinary ALA was increased 2-fold. 

Pollock CA, lbels LS. 1986. Lead intoxication in paint removal workers on the Sidney Harbour Bridge. Med JAust 145 635-639. 

Tons of spent abrasives result each year from the removal of old paint from bridges. Because the spent abrasives contain metals from the paint, some spent abrasives may be considered hazardous by the Toxicity Characteristic (TC) criteria. Incorporation of the spent blasting abrasives in nonstructural concrete offers an opportunity to recycle the spent abrasives while immobilizing potentially leachable metals. Solvents that are less aggressive will mean that abrasives will be necessary in some applications. Study results indicated that considerable quantities of these spent abrasives can be solidified/stabilized while reducing the leachability of cadmium, chromium, and lead and producing compressive strengths over 6895 kN/m2 (1000 psi) (Brabrand and Loehr, 1993). 

Fig. 6. Portable soil-washing machine shown here at a highway maintenance site used for removal of lead particles from the residue created when bridges and other metal structures are sand-blasted to remove old paint containing lead. There are numerous applications for such portable plants. (Westinghouse Electric Corporation)...

Four-tenth gram samples of paint from a bridge, analyzed for the lead content by a precise method (<1% rsd), gives a relative sampling precision, i , of 5%. What weight sample should be taken to improve this to 2.5% ... 

Corrosion concerns on cable-supported structures have been present from the early design. For example, galvanized zinc coating of the wires was used on the Brooklyn Bridge, which was completed in 1883. At that time, it was a standard practice to coat the wire with linseed oil, circumferentially wrap the assembled cable with soft galvanized wire laid into red lead paste, and to paint the finished cable. 

The problem of applying protective coatings to steel bridges to prevent corrosion involves the removal of the existing lead-based paint in compliance with environmental regulations. All wastes must be treated in accordance with congressional regulations. 

OSHA cited a bridge and water tower painter with violations of federal workplace safety and health standards for exposing workers to lead. The employer was blasting paint from two bridge overpasses. OSHA s inspection revealed nine alleged willful and two serious violations. Proposed fines total 321,000. 

The uncontained sandblasting of bridges or any exterior structure bearing lead-based paint can temporarily add hazardous amounts of lead to the air in the immediate vicinity and in communities just downwind from the work site. 

In addition, lead-based paint is still permitted for commercial and industrial uses. Because lead helps paint stand up to sun and harsh weather, it is often used for painting the exteriors of automobiles, boats, buildings, and bridges. Children s playground equipment may... 

Trilead tetroxide, red lead, minium, Pb304, is mixed with linseed oil and used principally as a paint to prevent the rusting of steel, particularly to objects exposed to the weather, such as ships, bridges and agricultural machinery. It is also used for making lead glass and special lead jointing compounds. 

Waste disposal is a national problem extending beyond the scope of bridge paints. Ihucedures developed by other industries may be appHcable to lead debris containment. The key to any approach is the economics of the processes. These numbers are often difficult to determine precisely because of the uncertain costs of hazardous waste disposal, and the larger uncertainties of whether a waste is hazardous to begin with. 

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