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Highly toxic chemicals are replacing the lead in our fuel, yet government authorities continue to underestimate the serious risks to public health. Part 2 JUNE -JULY 1995 LTHE COMPOSITION OF PETROL _-=' ast issue we discussed how there was linle evidence to support the claim that the octane-raising substances in unleaded petrol are safer than the lead compound used. ilII fact, there was little or no evidence to support the claim that lead in petrol has any effect on the levels of lead in the blood. Unleaded technology means something else is added to the petrol to maintain its octane number. What has not been made very clear is tha~ since about 1970 the lead content in leaded petrol has been reduced. Policy has meant that, over time, lower and lower maximum lead levels have been set. There are three main groups of substances the oil companies use ins.tead of lead. 1. Aromatics-organic compounds based Oill the benzene ring" a 6-carbon ring with 3 delocalised double bonds, e.g., benzene, toluene, xylene, etc. 2. Olefines;-{)rganic compounds 'which have double bonds. After combustion, one critical by-product is 1,3-butadiene. 3. Oxygenates-organic compounds containing oxygen molecules such as methane, ethane or MTBE (unethyl-tertiary-butyl ether). The US Environmental Protection Agency has targeted five toxic air pollutants-ben zene and I,3-butadiene are the top ,two on the list. They are both highIy carcinogenic sub stances. 1,3-butadiene has on'ly just come to international attention.' Tnerefore, tuere is one very important question to ask. What is the present composition of leaded, regular unleaded, and premium unleaded fuel? In Australia, oil companies do not have to refease the exact formulas for making up the petrol mixtures. In Britain it ,is the same as in Australia: the oil companies 'provide almost no information abou~ the chemical content of lead. In the US, oil companics have to release the petrol formulae to the US EPA. I managed to find an indepentlent stu'dy, done by Dr Michael Dawson and Mr Noel Child of the University of Technology, Sydney, which analysed the composition of many petrol samples from all over Australia.! Toey also compiled a table of petrol compositions from many other countries (see Tables 1,2 and 3). These figures came from the "International Gasoline Survey, 1994", a report published annually by Associated Octel Company. Using ~he figures for Australia as an example, tin regular unleaded petro.l, the total aro matic content was 7,7.7%, and benzene level at 2.0% (Table 2). But, for leaded petrol, the total aromatic content was 29.2%, and the benzene level at 2.1 % (Table 3). Wow! This means the total aromatic content and the benzene levels are very similar-actuaUy, mar ginally higher in leaded petrol. If you look at all the other countries in the tables, the per centage content of benzene and totaU aromatics in leaded and regular unleaded petrol is also very similar. Standard unleaded petrol has a lower octane number of around 91, whereas leaded petrol has an octane number of 96 or higher. The lead compound added is just enough to increase the octane number from around 91 to over 96. Premium unleaded has an octane number of 96, so it has much higher levels of aromatics-a~ well as benzene-than other fuels. For premium unfeaded petrol in AustraUa, the total aromatic content was 36.4%, with benzene level of 3.3% (Table 1). This analysis of Australian petrol was conducted before 1st January 1995. At ~his time, maximum lead levels were at 0.3 grams per litre. After 1st January 1,995, the maximum lead levels were reduccd to 0.2 gllitre, which means that more of these alternative addi tives-the aromatics, including benzene, and/or olefines-have been used. So, leaded petrol today could have even more alternative additives than regular unleaded petrol.3 NEXUS • 25