Ambient air, lead

Abulfaraj WH, Ahmed M, Mousli KM, et al. 1990. Measurement of ambient air lead concentrations in the city of Jeddah, Saudi Arabia. Environ Inter 16 85-88. 

Both gas sensors based on nontemplated and nanostructured PPy films were found to respond to a variety of solvent vapors, including methanol, ethanol, isopropanol, acetone, and also to humidity with a resistance increase. Initial tests were performed in ambient air leading to the observation of the following phenomenon, the sensors responded to water vapor with an immediate resistance increase, while exposure to organic solvents led to an initial small decrease in resistance before showing the... 

Fig. 2.3 Annual ambient air lead concentrations, by area, prior to the August 1974 and August 1975 surveys [8].

Ambient air lead receives the element directly from source emissions or through reentrainment of dust lead particles after deposition onto soils or through mobilization of industrial process dusts. 

Lead in dusts was discussed earUer as a factor in producing localized increases in ambient air lead from resuspension. Numerous smdies have... 

Environmental media of interest in this section on measurement are the same as those producing potential human lead exposures ambient air, lead paints, diet, drinking water, soils and dusts, and some of the more problematic idiosyncratic sources. Sampling and laboratory measurement techniques now widely used are emphasized with comparative statements for older methods provided mainly to offer perspective. Biomarker sampling and measurement methodologies, i.e., procedures for lead in biological media directly relevant to human lead exposures, are presented in a later chapter. 

Methodologies for air lead sampling and laboratory analysis are limited to specific reference methods officially prescribed to accommodate the fact that air lead analysis in the United States is directed to, among other purposes, compliance with an ambient air lead standard within the framework of State Implementation Plans (SIPs). SIPs are the regulatory and legal means by which the various states implement the nationally enacted ambient air lead standard. The details are discussed in such treatises as Chapter 4 of the 1986 U.S. EPA Air Quality Criteria for Lead document (U.S. EPA, 1986a) and Chapters 2 and 3 of U.S. EPA, 2006. The required reference methods for legal enforcement are codified in the CFRs (CFR, 1982, 40 58). 

Ambient air lead partitions into vertical gradients, especially near mobile lead sources, e.g., vehicular exhaust from leaded gasoline combustion. There is special emphasis on those heights above source relevant to human lead exposures. Other specific monitor locating requirements include specifications for distances from roadways (5—100 m) and distances from obstacles between the monitor and the emitting source (Appendix E, CFR, 1982, 40 58). 

The total suspended particulate (TSP) measuring networks, managed by local and state agencies, currently numbering about 250 sites, measure lead via official Federal methods (40 CFR Part 40, Appendix G) in particulate matter sized up to 30 pm. The retention of the TSP networks is driven by the regulatory stmctore of the previous and current ambient air lead primary and secondary standards. Locations of these sites are depicted in U.S. EPA (2006, Ch. 3). 

Three periods are covered in tabulating U.S. ambient air lead levels 1966—1974, 1975—1984, and 1985 to the present. The first interval captures the increase and peak in air lead from mobile (leaded gasoline use) and stationary (e.g., industrial, fossil fuel, and waste combustion) facilities. The second period overlaps the regulatory phasing down period for lead emissions to the air, while the final period of 1985 to the present represents the current picture for air lead levels. As noted earlier, inclusion of earlier periods with their much higher atmospheric lead burdens is intended to help quantify... 

Table 6.6 depicts ambient air lead statistics gathered by the U.S. EPA for 1973, the Seven-City Study of U.S. air lead for commercial, industrial, and residential monitoring sites. The U.S. cities were Chicago, Cincinnati, Houston, Los Angeles, New York, Philadelphia, and Washington, DC. Data reported are broken into monthly mean, minimum, and maximum values. 

TABLE 6.6 U.S. Ambient Air Lead Statistics for the Seven-City Study Chicago, Cincinnati, Houston, Los Angeles, New York, Philadelphia, and Washington, DC ... 

Ambient air lead comprises a significant source for human Pb exposures and is also a contaminated environmental compartment that arises from lead within waste streams emitted to the atmosphere. Unlike lead paint, air Pb s history has no identity as a lead product per se and is purely a contaminated medium encountered by various human risk populations. 

Candles represent another source of lead fumes and dust. Some candlewicks contain lead as a stiffening agent. Wasson et al. (2002) observed that burning a single candle in a room can raise the amount of lead in the air of that room above the ambient air lead concentration limit set by the USEPA of 1.5 pg per cubic meter (m ). This lead is in the air as fine particulates that can settle on furniture and floors. Although the Consumer Product Safety Commission (CPSC) banned the manufacture of lead-containing candle wicks in 2003, imported candles, and those purchased at yard sales and from thrift stores, may contain them. 

The study of ambient air lead concentrations has also shown the significant correlation between the combustion of leaded gasoline and soil lead concentrations. The EPA has noted that air lead concentration decreases as you travel from the center of a city and that soil lead levels are a direct function of the deposition of ambient air lead (see EPA reports for 1986). The contribution of leaded gasoline emissions and soil lead levels to interior house dust is evident in studies showing that lead in house dust is related to exterior lead levels (Chaney, 1989). 

It should first be noted that the drying conditions modify the parameters studied. Drying in ambient air leads to quite differences in certain parameters compared to those obtained after drying at 90" in air. Also, oxidation induced variations of thickness, which, from a certain temperature, also depended on the treatment time (9). 

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