Now tell me, have you ever sat in a traffic jam? Behind vehicles that are belching out diesel smoke? They smell awful, don’t they? But do you have any idea just how bad for your health these fumes really are?
Diesel engines can be powerful, very efficient and new ones can be very clean, but they have to be maintained well. Old worn out engines, badly maintained and badly adjusted don’t burn their fuel properly – and the resulting exhaust fumes are a chemist’s nightmare.
They are made up of two things: gases, that you cannot see, and black soot that you can. Together they can contain thousands of different chemical substances. The gases in diesel exhaust are bad enough: they contain such hazardous chemicals as acetaldehyde, benzene, 1,3-butadiene and formaldehyde – but the soot is even worse.
It consists mostly of tiny carbon shells which over time agglomerate into chains and eventually into clumps. These carbon shells quickly adsorb organic compounds from the incomplete burning of the fuel, including such cancer-causing substances as polynuclear aromatic hydrocarbons, together with. Even worse, according to a recent study by the Health Effects Institute, more than 98% of the particles emitted from diesel engines are tiny, less than 1 micron in diameter. These are especially dangerous because they get past the defense mechanisms that keep dust out of your lungs. Studies by Harvard University’s School of Health and the American Cancer Society have established strong links between circulatory and lung diseases such as heart attacks, strokes and asthma, and fine particles less than 2.5 micrometers in size (1/50 the diameter of a human hair).
And how do you feel about these particles penetrating into the lungs of your children?
Dr Jonathan Grigg and his team at the Institute for Lung Health at the University of Leicester in the UK looked deep into the lungs of children – and found diesel soot in all of them.
Are you asthmatic? Have you noticed that a cloud of diesel smoke can set you wheezing and coughing? The fine particles in diesel soot increase the production of a protein that triggers asthma attacks while suppressing a second protein that might otherwise keep symptoms under control.
It has long been known that individuals living in city areas or near busy roads are at much higher risk for asthma compared with those living in less busy areas. But now researchers in Cincinnati have found the cause. They discovered that diesel exhaust particles cause the immune system to secrete abnormally high levels of interleukin-6, a protein released in response to substances that the immune system identifies as dangerous. High levels of this protein can constrict the airways and start an asthmatic attack in susceptible people.
Normally, this immune system response is controlled by the production of a protein called interferon-gamma. Interferon-gamma works to slow down excessive immune responses. However, the Cincinnati researchers found that diesel exhaust appears to dampen interferon-gamma production – allowing interleukin-6 to trigger asthmatic symptoms.
Over 40 individual chemical compounds in diesel exhaust have been identified by the United States Environmental Protection Agency as compounds that cause cancer and listed as Toxic Air Contaminants. A study of the cancer risks from diesel in the 20 largest cities in the United States estimated that 1,210 cancers in the city of Pittsburgh were caused by diesel particulates. The UK government carried out a similar study and estimated that 24,000 people in the UK die each year from diseases caused by diesel soot.
It may take many years after the exposure starts for diesel-related cancer to develop.
Exposure to diesel exhaust in combination with other cancer causing substances may increase your risk of developing lung cancer even more. Other substances that are known to create a high risk of lung cancer include cigarette smoke, welding fumes and asbestos. Exposure to diesel exhaust in addition to these substances greatly magnifies the risk of lung cancer, and is particularly dangerous.
Other studies have suggested that people exposed to diesel exhaust are more likely to have chronic respiratory symptoms such as persistent coughs, bronchitis, and reduced lung capacity than unexposed people. People with pre-existing diseases, such as emphysema, asthma, and heart disease, may be more susceptible still to the effects of diesel exhaust.
Studies in animals suggest that diesel exhaust may have other effects as well: mice developed skin cancer when their skin was exposed to extracts of diesel exhaust; diesel exhaust caused lung damage in laboratory animals and exposure to diesel exhaust reduced animals’ resistance to bacterial infection.
With diesel fumes being such an obvious health hazard, reducing them would seem to be an important objective from the viewpoint of public health. But the issue is not that simple. It’s not enough, for example, to encourage people not to use diesel engines. They are essential for such vehicles as lorries and buses, and compared to petrol engines, well maintained diesel engines are more fuel efficient, last longer and emit less greenhouse gases per mile.
But how do we persuade owners to look after them properly? To replace worn out engines, maintain them properly and keep them properly adjusted? Diesel fumes are completely controllable. By proper maintenance which will also save the owner money in terms of saved fuel, more power and reduced breakdowns.
So, the next time you see a bus, or a matatu, or a lorry, or a car belching out black diesel smoke, don’t just curse, get really mad! Get the number of the vehicle if you can see who it belongs to and complain to them. Lobby your MP and councillor to put pressure on them. Refuse to travel on a bus that is trailing black fumes. It’s not just a case of having a nice clean journey to work. Those fumes are seriously affecting your health – and that of your children.
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