Dust, lead from roadways

A second factor may be emergence or existence of a floor to further atmospheric Pb emission declines in certain locales. For example, modeled estimates indicate that 90% of the atmospheric Pb particulate loading in California is attributable to reentrainment of leaded roadway dusts from roadways contaminated over past decades by leaded gasoline combustion and fallout (Harris and Davidson, 2005). Lankey et al. (1998) noted that resuspension accounts for 40% of Pb emissions in the South Coast Air Basin of CA, while a much higher fraction of 75% was reported for lead resuspension in an Armenian city (Kurlgian et al., 2002). 

EPA, 2006). Reentrainment of lead in particulate back into the atmosphere from dusts and soils after initial deposition of lead from the atmosphere also occurs due to atmospheric mobilization (Cowherd et al., 1985 U.S. EPA, 2006). The range of lead transport via the atmosphere can be many miles for the smallest size particles to as short as meters for reentrained dust particles at roadways for heavy traffic or for large lead paint particles, as occurs with weathering and flaking of lead-painted surfaces in older buildings where particles are mobilized to nearby soil surfaces, around the drip line."... 

However, lead inputs to a more localized atmosphere can occur by reentrainment of lead from depositional sites such as roadway soils and dusts to the contiguous atmosphere. Other sources of reentrained dust lead are fugitive dusts mobilized from point source waste storage or persisting surface contamination. The long half-life of lead in these media assures that resuspended lead levels in the atmosphere will pose exposure problems for future decades. 

Of the six heavy metals discussed in this chapter, Pb has been studied extensively with respect to the environmental effects. Clair Patterson, the father of environmental Pb studies, in one of his many major publications concerning the global Pb cycle (Patterson and Settle, 1987), noted that during pre-industrial times Pb in the troposphere originated from soil dusts and volcanic gases. In modern times (1950-1980) the proportion of natural Pb in the atmosphere is overwhelmed by the industrial sources of smelter emissions and automobile exhausts. Lead air pollution levels measured near our Nation s roadways decreased 97% between 1976 and 1995 due to the consequence of the Clean Air Act that eliminated leaded gasoline which interfered with the performance of catalytic converters. 

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