Lead content of petrol and diesel and its assessment in an urban environment.

Pakistan is one of the few countries in Asia that continues to use only leaded-petrol as vehicular fuel. The concentration of Pb in its petrol reported in 1991 was the highest (1.5-2.0 g Pb L(-1)) of all produced by the various Asian countries and far exceeded the WHO's guideline of 0.15 g Pb L(-1). We have undertaken a study to trace and quantify this toxic element in the environs of Karachi. Pakistan's major metropolis, having more than 30% of the nation's total number of vehicles. In this article we report the Pb contents of petrol and diesel currently manufactured and marketed in the city. Samples of 'Regular' petrol collected in 1999 was found to contain 0.363 g Pb L(-1) (range: 0.335-0.390 g Pb L(-1)), a factor of 5 lower than that marketed prior to 1991. Its concentration in diesel fuel was much lower (0.017 g Pb L(-1)). Based on the available statistical data on the type and volume of vehicular traffic, we assessed that the current lead emission from vehicular traffic into the atmosphere is 391 metric tons a year, which is a factor of 2.7 lower than that estimated for 1989.