When the Department of Minerals and Energy confirmed earlier this year that leaded petrol would be phased out completely by 1 January 2006, environmentalists and public health experts were delighted.
Drivers of older vehicles that can’t use unleaded petrol were reassured by reports that a ‘special additive’ would render unleaded petrol viable for older cars.
But the additive – a form of the metal manganese – could be as bad as lead ever was.
Why is metal added to petrol?Most cars produced after 1996 can use unleaded petrol; however, if you have an older model car this might damage the engine. One ‘solution’ to this is to use fuels that contain other metals, such as manganese, to perform the same function as lead did previously.
Lead was previously added to all petrol to boost its octane rating, which is a measure of the petrol's ability to prevent ‘knock’, a type of undesirable combustion in the engine.
What’s wrong with lead?
The negative effects of lead are well recognised and documented by numerous international studies, including those conducted by the Medical Research Council (MRC). Exposure to environmental lead, to which leaded petrol has been a significant contributer, is particularly harmful for young children. It interferes with the developing brain, and may lead to learning and behavioural problems, anaemia and abnormal organ development.
MRC research found that South African children living next to refineries or highways had levels of lead in their bodies 10 times higher than those allowed by World Health Organization guidelines. Studies also show that children’s blood lead levels have dropped since the introduction of unleaded petrol.
The other advantage of unleaded fuel is that catalytic converters can be fitted to many cars. These converters greatly reduce the release of other harmful chemicals in vehicle exhaust.
What’s wrong with manganese?
Medical scientists are concerned that manganese in exhaust fuel could also pose serious health risks. It is well established that manganese is toxic in high doses: like lead, it can impair many organ systems, most notably the brain. ‘Manganism’, a type of Parkinson’s syndrome, refers to a cluster of symptoms – e.g. impaired co-ordination and mental functioning – observed in some individuals exposed to very high levels.
MMT (methylcyclopentadienyl manganese tricarbonyl), a manganese-based additive, is the lead fuel replacement of choice in certain parts of the country. For instance, Caltex plans to install an MMT tank to replace the lead tank at its Milnerton refinery, the Cape Argus reported on Tuesday.
What has not yet been established is how dangerous exposure to the lower levels of manganese entering the environment from MMT-dosed petrol will be. Research into this problem is ongoing by bodies such as the U.S. Environmental Protection Agency and the MRC.
Aren’t there any other options?
Richard Worthington, spokesperson for Earthlife Africa Johnnesburg, points out that there are options open to the petrochemical industry apart from metal additives.
“We’re pleased that moves are being made – if slowly – towards reducing the negative effects of petrol. But our stand is that all heavy metals should be removed, and replacing lead with manganese is changing rather than solving the problem."
"We know that it's possible to increase the octane rating of fuel without using metal additives, because these technologies exist in other countries. The argument the petrochemical industry uses is that it would cost too much to make the necessary changes to the refining process.”
“We aren’t sympathetic to the cost argument, because the industry has been benefiting for years by not paying for the public health impact of fuel emissions."
No petrol is 'clean'
With all the fuss and bother about additives and new fuels, we tend to forget an important fact: there is no such thing is ‘clean’ petrol - leaded, manganesed or ‘un-’. All petrol is damaging to human health and the environment, and fitting a catalytic converter doesn’t mean your exhaust pipe starts emitting flowers.
This is not to say that recent efforts to reduce the negative effects of petrol exhaust should be derided, but they also shouldn’t let us feel we’re off the hook in terms of causing air pollution as motor vehicle users – and suffering its effects. Even petrol that doesn’t contain heavy metals will still result in plenty of other unsavoury pollutants, and will continue to worsen global warming.
(Olivia Rose-Innes, Health24, September 2005)
Mathee, A and von Schirnding, Y. 2004. Environmental lead exposure and child health in South Africa. Medical Research Council.
Rollin, H et al. 2005. Blood manganese concentrations among first-grade schoolchildren in two South African cities.
Environ Res. 2005 Jan;97(1):93-9.