Black bus smoke and cancer

Back in 1996, shortly before a general election, the then minister for the environment was doing his rounds visiting his constituents. At one of these visits a constituent expressed concern about the health implications of the black smoke emitted by diesel vehicles, especially buses. The minister reassured the constituent that the problem was shortly to be solved by the introduction of a fleet of modern buses. At the same time he pressed a little cloth teddy bear with his name emblazoned on its tiny sweater into the constituent's hand by way of reassurance or, maybe, to encourage a favourable vote.

Now, 10 years later, most of the old buses are still on our roads emitting dense clouds of choking black smoke. Some of the new buses which have been introduced are doing this too. Rumour has it that this is partly because the buses (and possibly other vehicles) are not being run on proper diesel fuel but some other cheap substitute, possibly light heating oil. If there is any truth in this, it appears that this practice is easily detectable by the simple expedient of testing the specific gravity of the fuel in the vehicle tank at the roadside.

The public should be aware of the serious threat to health posed by diesel exhaust (along with other pollutants from exhaust emissions). Diesel exhaust consists of fine soot-like particles referred to as "PM 10 particulate" which is highly toxic. If the smoke can be smelled and is actually visible, it denotes very heavy pollution. Large-scale epidemiological studies have consistently shown an association between exposure to particulate air pollution from diesel exhaust and lung cancer deaths. This applies particularly to people living in streets with high levels of traffic, which is the case in most of Malta.

In plain language: the black smoke emitted by buses is known to cause cancer - this is especially so if you can easily see it and smell it. The cancer usually occurs many years later. So if you cannot avoid regularly inhaling black smoke when out walking in our streets or if you live in a heavy-traffic area, your chances of developing cancer in 10 to 20 years' time are increased significantly.