[Effect of the lead-petrol-law on the contents of lead and benzo(a)pyren in urban environmental dust (author's transl)].

For the purpose of evaluating the stress on citydwellers by pollutants emanating from traffic sources the contents of lead and 3,4-benzpyrene in sedimentable city dust were determined in samples collected at 46 sites with different traffic densities in a city of medium size but considerable overall traffic volume (Erlangen, Bavaria). To estimate the effect of the gasoline-lead-law of Aug 5, 1971, determinations were carried out both in 1971, i.e. before this law came into effect, and in 1977 when the lead content in gasoline was finally limited to 0.15 g/1. The following results were obtained: - In city areas with dense traffic, the medium lead content dropped from 4.2 to 2.2 mg/g of dust, and the medium 3,4-benzpyrene concentration dropped from 1.3 to 0.5 microgram/g of dust. This amounts to a reduction of both the lead and 3,4-benzpyrene contents in city dust by about one half. - In the city periphery with lesser traffic density, the lead and benzpyrene contents, resp., were originally lower by about one half. In the case of lead, the concentration dropped from 1.9 mg to 1.2 mg/g dust, while 3,4-benzpyrene dropped from 0.6 to 0.4 microgram/g dust. Thus, the beneficial effect of the gasoline-lead-law was less obvious in these low-traffic parts of the city area. - The decrease in 3,4-benzpyrene with decreasing lead content is remarkable (striking, a striking pheromeron) and may be explained by lesser emission of this pollutant when burning gasoline low in lead.