Why Do Exhaust Fumes Contain Lead?
The lead in exhaust fumes comes from the petrol used to drive the internal-combustion engine. Crude oil straight from the wells is thick, black and sticky. It has to go through a complicated refining process before it can be used as fuel for the engines of cars, lorries, buses and aircraft.
During refining, various substances are added to improve the petrol and for other reasons. For instance, small quantities of dye are put into standardize the color. Other substances prevent the formation of the gum which would clog up parts of the engine. Lead, in a liquid form called tetra-ethyl lead, is added to petrol to reduce “engine knock”.
This means that it prevents the petrol from igniting in the engine at the wrong moment. When an internal-combustion engine is running, the petrol is lit by sparks from the sparking plugs. The petrol burns in what is really a series of small explosions and produces gases which come out through the exhaust pipe as dirty, smelly fumes and the lead comes with them. Ill-health can be caused if quite small quantities of lead in air are inhaled over a long period of time.
For this reason, the governments of such countries as the United States, Britain, Sweden and Japan are passing laws to reduce the amount of lead in petrol. They are also encouraging car manufactures to design internal-combustion engines which will work efficiently on lead-free petrol and have cleaner exhaust fumes. These engines will be more expensive at first, but they will help to make the air cleaner where there is a lot of traffic.
Motor vehicle emissions contribute to air pollution and are a major ingredient in the creation of smog in some large cities. A 2013 study by MIT indicates that 53,000 early deaths occur per year in the United States alone because of vehicle emissions. According to another study from the same university, traffic fumes alone cause the death of 5,000 people every year just in the United Kingdom.
The largest part of most combustion gas is nitrogen (N2), water vapor (H2O) (except with pure-carbon fuels), and carbon dioxide (CO2) (except for fuels without carbon); these are not toxic or noxious (although carbon dioxide is a greenhouse gas that contributes to global warming).
A relatively small part of combustion gas is undesirable, noxious, or toxic substances, such as carbon monoxide (CO) from incomplete combustion, hydrocarbons (properly indicated as CxHy, but typically shown simply as “HC” on emissions-test slips) from unburnt fuel, nitrogen oxides (NOx) from excessive combustion temperatures, and particulate matter (mostly soot).
Many people are aware of the lead in petrol and are concerned about what effect it may have on the health of their family. This is especially so if they live on a busy road or their child attends a childcare centre in a “heavy traffic” area. The Lead Advisory Service (NSW) will answer any questions that you may have about lead, but here are some automotive “lead” facts of interest.
The National Health and Medical Research Council has set an Australian National Goal for ALL Australians to have a blood lead level below 10 µg/dL (micrograms per decilitre). For every 10µg/dL of lead in the blood, experts agree, that a child is at risk of losing between 2-3 IQ points. Lead also damages kidneys, hearing and physical growth. It causes learning difficulties, behavioural problems, tooth decay and many other long term serious health effects.
Children under the age of seven years are particularly at risk of damage because their brains and nervous systems are still developing. Between 36,600 and 221,620 NSW preschoolers are estimated to have blood lead levels above 10µg/dL.
Allowing $5,190 in additional remedial education costs, lost earning potential and additional health costs per IQ point lost, means that the estimated cost to the community is between $303 million and $2.8 billion. This does not include older children, adults or the cost of even higher blood lead concentrations!
The fallout from leaded petrol exhaust fumes not only pollutes the air we breathe with microscopic lead particles (amongst other pollutants), it is also responsible for adding to the lead content of household dust, soil and ceiling void dust in our homes. Because of their extra hand to mouth activity this dust is a major contamination pathway for small children, especially during renovation or demolition of pre 1970 buildings when the dust from areas such as roof voids or wall cavities is released. Add to this dust, the risk from lead paint that may also be disturbed during works, and you have a typical case of a young urban child – lead poisoned by the combination of sources of lead – paint, petrol and industry.
A recent Public Health Unit study found that children’s blood lead levels rise 1 µg/dL for every 10,000 cars per day going past their childcare centre. Every gram of lead from petrol, put into the environment now is adding to the thousands of tons of lead from petrol which already contaminates our cities. So the lead petrol problem is not “going away” we’re simply slowing down the rate of further contamination of our children’s environment.
Over 100,000 (40%) cars in NSW could be using unleaded petrol (ULP), but are still using leaded. The NRMA recently published an article to help counter the lead additive manufacturers media campaigns which try to persuade people that leaded petrol is safer than unleaded. The levels of benzene in leaded and unleaded petrol in Australia are essentially the same. Overseas examples are not relevant to Australia and their situation is NOT OURS.
Since 1993 the Federal government has made $352 million from the leaded fuel tax which was levied because of the recognised health and environment risks attributable to lead. This money could be used to subsidise the more environmentally friendly MTBE (methyl tertiary butyl ether) additive and lead education campaigns. At the moment this lead fuel tax goes to consolidated revenue and less than 1% has been spent on dealing directly with lead.
Old cars would not have to be retired and the new MTBE fuel need not be any more expensive for consumers than leaded fuel is now. They would just switch to the new product and everyone’s lead levels would start to decrease accordingly. There is ample evidence to suggest that the general lead body burden of the population reduces in line with the reduction of lead in petrol. This has been shown to occur dramatically in other countries where lead has been removed from petrol.
Australian children are still dying and permanently injuring their health by sniffing petrol. Although sniffing any petrol is harmful to health, it’s the lead in petrol that kills or leaves petrol sniffers with permanent brain damage. Transport plans need updating to encourage public transport and reduce the overall need to travel by car. The gains made in Sydney’s air quality by the introduction of ULP and catalytic converters are being overtaken by the increase in the number of cars and the distance travelled annually by each car. The amount of Australia’s greenhouse gas emissions produced by motor vehicles is 21%. Britain has recently made radical changes to its transport policy to reduce dependence on the car, halving the budget for new roads.
The heavy metal pollution of Sydney Harbour is considered to be contributed to significantly by urban runoff, including the substantial amount of leaded petrol exhaust particles which settle on roadways and are eventually washed into stormwater drains and then our Harbour. Sydney waterway sediments have mineable levels of lead and other heavy metals.
In August 1997 the new Clean Air Regulations were passed and leaded fuel can contain a maximum of 0.2 g/L. Unleaded petrol can contain 0.013 g/L. Shell half lead contains 0.1 g/L Australia is at risk of becoming the last developed country to ban lead in petrol. Leaded petrol was banned in Japan in 1986, Austria in 1990, Canada 1993, the US in 1995 and New Zealand in 1996.