Airborne lead from vehicle exhausts

Tetra-ethyl lead is added to petrol as an anti-knock agent. When the petrol is burnt in the engine, the organic lead is converted to inorganic compounds. Ethylene dibromide is added to the tetra-ethyl 

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This extensive usage of lead has given rise to widespread environmental contamination. In rural areas ambient lead levels are usually below 0.2 jug/m in remote areas of the world one or two orders of magnitude below this, and in urban areas one order of magnitude above, with values up to 10 jUg/m not infrequently recorded in dense traffic. Over one-half and up to 90% of the airborne lead is derived from vehicle exhausts, the remainder from refuse incineration, fossil fuel combustion and from industrial sources such as smelters, iron and steel works and lead processing plants. 

Excerpt 4E is taken from an article in Chemical Research in Toxicology and involves the toxicity of fine particulate matter, airborne particles with effective diameters <2.5 pm (also known as PM2 5). The fine particulate was collected using a PM2 5 monitor. Ambient air is pulled through the monitor, diverting the larger particles (>2.5 pm) and capturing only the smaller ones onto a filter. Such fine particles arise from a number of sources including industrial emissions, vehicle exhaust, and forest fires and may lead to asthma, bronchitis, and possibly cancer. 

Although efforts are now being made in several industrialised countries to reduce this form of pollution, the total amount of lead which is continually being discharged from motor vehicle exhausts is still very great. Lead from this source probably makes the greatest single contribution to lead in the atmosphere and in some urban areas, this source may account for over 90 percent of airborne lead [14]. 

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