Buses' black smoke

Herman Grech's report 'Large vehicles running on hazardous fuel cocktail' (The Sunday Times, August 17) raises an important health issue relating to tampering of engines and the criminal use of light heating oil by owners of large vehicles, predominantly buses.

Sulphate particles have been shown to be associated with bronchitis, chronic cough and exacerbation of asthma. But this is only the tip of the iceberg. The black smoke emitted by most of our buses is far more dangerous than suggested by the article. This is an abundant source of toxic chemicals which are carried into our lungs when we inhale air polluted by these sooty particles. Such toxic soot particles are referred to as 'particulates' and these particulates are more dangerous than sulphur compounds.

Until recently, there was uncertainty as to which of the various pollutants, which include sulphur and nitrogen compounds, ozone, benzene and particulates, was the most dangerous. There is now strong scientific evidence that particulate emissions, especially from diesel engines, represent the greatest health threat by causing an increase in the incidence of lung cancer in addition to other causes of death.

The threat to health posed by these particulates is summed up by the conclusions in a report drawn up by a WHO working group in January 2003: "Long-term exposure to current ambient particulate concentrations may lead to a marked reduction in life expectancy. This is primarily due to increased cardio-pulmonary and lung cancer mortality. Increases are likely in lower respiratory symptoms and reduced lung function in children, and chronic obstructive pulmonary disease and reduced lung function in adults."

Exposure to the current level of pollution in Europe was calculated to be responsible for shortening life expectancy by 8.6 months but the impact may vary from around three months (as in Finland where pollution is low) to more than 13 months (as in Belgium where pollution is higher). This is probably a conservative estimate. It has been suggested that the decrease in life expectancy of people living in the most polluted cities (for which read Malta), relative to those living in cleaner cities, might be higher and measured in years rather than months.

The results of air quality monitoring in Malta indicate a high level of pollution with particulates and other traffic-related pollutants and the presence of 'hot spots' where the pollution is particularly intense.

Most of our buses are adding significantly to this pollution and endangering our health by illegally tampering with fuel and engines to save money. The evidence of this is the black smoke emitted by these buses. That our government allows this abuse to continue is a national disgrace.