'Alarming level of dust in air'

Harmful fine dust particles produced by soft stone quarries amounts to at least 1,200 tonnes a year, a study has shown.

This works out roughly at a two-litre bottle full of what is technically known as particulate matter (PM10) for every person living in Malta annually.

The study results have just been published by Alfred Vella and Renato Camilleri in the scientific journal Xjenza.

Fine dust particles are a major component of air pollution that threatens both health and the environment as it is among the most harmful of all air pollutants. When inhaled, these particles evade the respiratory system's natural defences and lodge deep in the lungs.

Such particles can originate from a host of sources. The State of the Environment Report, published recently by the Malta Environment and Planning Authority, says that sources of particulate matter include atmospheric sea salt that originates from sea spray, dust - both local and brought about by winds from the Sahara - and tyre and brake abrasion and emissions, both from cars and industry.

Particulate matter also results from the incomplete combustion of fuels and lubricants. Mepa's report states that more studies had to be carried out to identify the sources of such particulate matter in Malta.

The study by Prof. Vella and Mr Camilleri, entitled Fine Dust Emissions From Soft Stone Quarrying In Malta, shows that the fine dust emission rate from the 67 active soft stone quarries stood at 11,500 milligrammes per square metre a day. The international guideline ranges between 100-300 milligrammes per square metre a day - meaning that, at best, the emission measured was 38 times more than the highest international recommended level.

The authors of the paper conclude that dust from the quarrying industry may be a significant contributor to lowering air quality standards in Malta with possible impact on the health of the population and the construction workers themselves.

This is the first study that has aimed to quantify the level of pollution from quarries. The authors say that the fine dust is produced both in the stone cutting as well as the dressing process, and that the estimate of 1,200 tonnes was a conservative figure.

An estimated additional 15 per cent of such fine dust is found with the more coarse dust that settled practically immediately within the confines of the quarry and which is whipped up in the air when disturbed by machinery and trucks. In addition to this dust, one has to consider the unquantified amount thrown into the air while stones are being carried to the construction site, by stone dressing on building sites and by stone and trench cutting and polishing. A case in point are the paving works in hand at Mdina, where residents have been complaining about the dust spewed in the air by stone polishers. Prof. Vella and Mr Camilleri reported that the soft stone industry utilised primitive techniques to extract and process limestone, and, considering that most quarries were situated very close to urban areas, the air quality was likely to be significantly affected by such emissions.

The authors suggest that wetting the stone while being dressed and cut would significantly decrease the amount of harmful dust emissions.

The State of the Environment Report says that the EU threshold of 50 microgrammes per cubic metre was exceeded on 37 out of 99 days at Floriana and on five out of 148 days at Kordin.

The pollutants were found to contain nitric acid, sulphuric acid, ammonium sulphates and ammonium nitrates as well as diesel soot. The particulate matter at Floriana is likely to be caused by traffic as the 300 microgrammes levels were recorded mostly during morning rush-hour traffic.

Contacted for his reactions about the findings, ENT surgeon Alec Lapira said the study on the incidence and distribution of diseases suggested interaction between pollutants and inflammation of the mucous membrane of the nose, known as rhinitis.

Particulate matter, which can range in size, is very problematic because the finer the particles the deeper they penetrate into the respiratory tract, ending up in the lungs. These particles are smaller than 10 microns in diameter - about one-seventh the thickness of a human hair.

Health problems begin as the body reacts to these foreign particles. PM10 can increase the number and severity of asthma attacks, cause or aggravate bronchitis and other lung diseases, and reduce the body's ability to fight infections.

Although particulate matter can cause health problems for everyone, certain people are especially vulnerable to PM10's adverse health effects.

Of greatest concern are recent studies that link PM10 exposure to the premature death of people who already have heart and lung disease, especially the elderly. Studies have shown an increased risk of ENT symptoms with regard to high PM10 concentrations.