Tetraalkyllead vapour

The uptake of inhaled tetraalkyllead vapour is regulated by a reversible transfer from the air in the lung to the blood as it circulates through the lung. 

The initial uptake of the inhaled vapour has been measured in 3 adult male subjects exposed for 1-4 min to ° Pb labelled tetraalkyllead at 1000 jug nf. The uptake was ca. 50% for tetramethyllead and ca. 40% for tetraethyllead [14]. These values probably approximate to the equilibrium uptake, due to the rapid 

Subject Motorway Roundabout General urban Car park 

Average 11.3 breaths per minute, is the number of experimental exposures. 

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The scientific literature has shown a wide variety of concentrations for tetraalkyllead vapour in air. These are best considered as a percentage of total lead in air, since this allows comparison of data from different sites without the need to correct for the effect of topography and meteorological conditions at the time of sampling. Even these percentages vary widely, but Harrison and Perry [16] have argued that many of the disparities have arisen from the use of non-specific analytical techniques. Values appear far more consistent if... 

The second form of organic lead in air is that associated with atmospheric particles. At an urban site in England, Harrison and Laxen found that this accounted for 0.2-1.2% of the total particulate lead [18]. At that site the mean atmospheric concentration of particle-associated organic lead (0.015 jug was rather less than 10% of total organic lead in air, the mean tetraalkyllead vapour concentration being measured as 0.16 Mg [19]. 

It might be anticipated that pollution transported from urban areas would be the major source of organic lead in rural air, since it is the major source of inorganic lead. This being the case, since the sinks for both inorganic and organic lead in air operate rather slowly, similar ratios of tetraalkyllead vapour to total lead might be expected in rural air as are observed in urban air. 

Fig. 2.8 Time-weighted pollution rose for tetraalkyllead vapour measured at three rural sites around Lancaster, [15].

Not all of the lead in the atmosphere occurs as particulate inorganic lead. Between 1 and 6% of atmospheric lead occurs as tetraalkyllead vapour (Section 2.3). Thus the typical British urban dweller will inhale 0.2-1.2 Mg(Pb) day" of tetraalkyllead. 

The formed tetraalkyllead is separated by the distillation with water vapour. 

This may take two forms. The major part consists of vapour phase tetraalkyllead compounds which may be separated from inorganic lead by filtration of an air sample. A small portion of the organic lead exists in association with atmospheric particles, and probably takes the form of tetraalkyllead or trialkyllead salts adsorbed upon particulate air pollutants. 

At most sites the typical contribution of vapour phase tetraalkyllead to total lead lies within the range 1-6%. Figures taken from a recent review article are given in Table 2.6. It has been pointed out that at roadside sites the chief determinant of tetraalkyllead as a percentage of total lead is the predominant vehicle driving mode [17]. Alongside British motorways where vehicles travel at high, constant speeds tetraalkyllead may account for as little as 1% of less total lead. At urban sites affected by stationary vehicles, cold choked vehicles or... 

Chau et al found that tetraalkyllead compounds have high vapour pressures and are not stable in water. It is observed that water containing 4.2 yg/1 Me Pb decreased to 2.8 and 3.9 yg/1 when stored respectively at room temperature and at 4 C overnight. 

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