Every breath you take

The head of the Chemistry Department and Dean of the Science Faculty at the university for the last eight years, Alfred Vella has been involved in numerous studies related to marine and air pollution.

He tells Natalino Fenech of his concerns.

What made you take up studies related to air pollution?

Probably because I was never convinced about the dictum that was always banded about by politicians in the 1970s that we have no air pollution problems because our country is always windswept. Wind action was believed to act as a sort of panacea allowing us to do what we like to the atmosphere without having to pay any price because wind will sweep all problems away.

While locally there were no obvious signs of air pollution as frequently evident in other countries, as in episodes of visible smog or acrid odours, the idea that our air appeared reasonably clean but in fact probably wasn't nagged in my mind because we too had a power station and an increasing number of cars and trucks on the road that obviously were releasing a lot of exhaust.

What was the first study?

The first study was, I would dare say, the first ever serious Environmental Impact Assessment to be carried out locally. The environmental group Zghazagh Ghall-Ambjent had asked me and a few others to counter a report, which the government had commissioned, about the impacts of the then newly proposed Delimara power station. In that report, I used a mathematical model to predict how much emissions would be released from the power station and where these flue gases were likely to cause most impact at ground level. The pollution plume footprint originating at the Delimara chimney was expected to be aligned with the wind direction which, thankfully, leads it out to sea for most, but not all, of the time.

Besides studies on air pollution you had also been working on other forms of pollution, right?

I always try to channel my senior chemistry students into studying subjects that are of relevance to the local environment. A lot of useful work has been done by students reading for their first degree or in their post-graduate work. A few chemistry graduates have remained working at the university where they give valuable assistance in research but very little money is available to pay for this kind of assistance. Thanks to such studies, most of which have been published in the international scientific literature, we have learnt a lot about the presence, in our environment, of a number of contaminant materials among which, and most notably, substances called organotins, which originate in antifouling marine paints containing a substance called TBT.

I was introduced to this particular environmental contaminant in the mid-1990s by my colleague in the biology department, Victor Axiak, who had been looking at the biological effects of the compound in marine organisms. A lot of this work was initially performed by Bernardette Aquilina, then working on her Masters degree: thankfully, she is still helping in the lab, having returned to work after a break of some years during which she attended to parental duties. We managed to show that TBT was ubiquitous in certain marine organisms but also in seawater and sediments around Malta and in Gozo.

Later work in our laboratory revealed that TBT and its decomposition products were transforming chemically in a way that made them volatile so that when silt dredged from harbour basins is landed, it has the capacity to become a source of air pollution by release of these TBT-volatile forms. Although the effect of exposure to these gases has yet to be studied, we know that these substances are harmful compounds and the less there are of them around, the better.

Use of the anti-foulant TBT in marine paint is now being phased out, so the problem is bound to diminish but it will not go away for many years to come.

TBT has already been banned in paint for small sea craft and a complete ban is due in 2008. That does not mean that ships and boats coated with it will not continue to ply our shores or come to be refitted here. Besides which, even after TBT is completely banned, its levels in contaminated marine sediments will remain high for many years before they are completely degraded.

The levels of TBT in water and sediments that we had found during the late 1990s make Malta one of the world's capital cities of TBT pollution. I do not want to sound like a Cassandra, but I do get shivers down my spine hearing about the need for even more yacht marinas around Malta, as such marinas constitute a main source of seawater pollution. One has to keep in mind that even with TBT gone, yacht hulls still need to be coated with new biocide-containing paints: one hopes these new compounds do not prove to be more problematic than the tin compounds.

A study which will soon be presented for publication reveals that TBT-containing particles are or have been floating around in our air as well. As far as I know, this has never been reported from anywhere else and you might say we may risk acquiring a reputation for negative first records. But this is the way it is unfortunately.

Collection of deposited dusts during 2005 from several places around the islands, mainly from roofs of school buildings, showed that TBT was present practically everywhere we sampled. In addition, a huge concentration of TBT-containing matter was found in dust collected from around the drydocks area; another minor but significant peak in dust-TBT was also found near Zurrieq.

We think this contamination derives from the practice of paint removal by grit-blasting or scraping of ships' and boats' hulls, respectively, which obviously takes place in these localities. Interestingly, we also found higher levels of TBT in dust from villages just downwind from the Maghtab area, which we think might derive from old "empty" tins of antifouling paint and discarded grit blasting material buried in the junk heap up there.

So your first study on air pollution was a theoretical one based on modelling emissions. Which was the first to determine air pollutants quantitatively, what were the findings and what was your reaction to them?

The first study was conducted in 1990 and published three years later: it was a determination of sulphur dioxide in air as measured in a number of localities mainly in the south of the island. We had to construct the equipment ourselves: this was placed next or on appropriate buildings where it couldn't be vandalised or stolen and frequently we made use of police stations or roof tops of willing residents.

The study showed that the concentration of sulphur dioxide in air depended strongly on atmospheric conditions and especially on wind direction: one-hour average concentrations as high as 320 microgrammes per cubic metre were measured in Marsa and other values (in the same units) were 218 for Hamrun and 161 for Paola; the guideline value for short-term exposure (for dusty air) is 125 microgrammes per cubic metre according to WHO.

Sulphur dioxide is an acidic gas which irritates the respiratory system and affects lung function; it also attacks masonry and is one cause of acid rain. In Malta, the most prevalent winds blow from the North West and these winds direct the pollution plume from the Marsa power station onto Paola and its environs. When SO2 was sampled with a NW wind blowing, one-hour average concentrations higher than 100 microgrammes per cubic metre were generally found in this locality. This was the situation almost 25 years ago: today, ongoing measurements carried out by Mepa show that the air quality with respect to sulphur dioxide pollution has improved significantly mainly because of the introduction of expensive low sulphur fuel at the power stations.

In a later study, we looked at atmospheric pollution from another angle: we used the external walls of churches in different towns in Malta as indicators of atmospheric SO2 pollution in their vicinity. We hypothesised that attack by the gas of the limestone walls of belfry towers must leave a chemical signature that we would be able to discern and that this signature, which we called "sulphation" would be more intense in those places where the gas was a frequent and abundant occurrence.

Indeed, we found this to be true; we mapped "sulphation contours" for Malta which showed that sulphation of walls of churches close to the Marsa power station were seven times higher than those only a few kilometres away. The signature was clearly evident in churches as far away from Marsa as Mdina and Rabat and was marked in Hamrun, Luqa, and especially in Paola which was greater than double that for the Marsa church. Significantly, none of the Gozo churches had sulphated belfry towers. So the wind, which was claimed to be our sweeper and saviour, was actually spreading and dissipating the pollutants, but not quite ridding us of them.

Recent measurements by Mepa have shown a decrease in atmospheric concentration of benzene, a cancer causing agent. Undoubtedly you see this as very positive.

It is indeed positive news. We had carried out first studies on the presence of benzene in both outdoor and indoor air.

In indoor air, benzene forms as a result of cigarette smoking. We had found alarming levels of benzene in two pubs in Paceville, well above the safe limit, if a safe limit can be said to exist for this particular poison. Again, this was before the smoking ban in public places came into effect. That ban was a very good move indeed and we have reason to be proud to have been among the first European states to bring about civility and safety in places where people meet to enjoy company.

Also positive was the elimination of leaded petrol and the use of petrol with a much lower content of benzene. I would like to see all filling stations and, in particular, the Birzebbuga Enemalta fuel depot equipped with vapour recovery systems in order to prevent loss of carcinogenic vapour containing benzene and other petrol components into the air while fuel tanks are being re-filled by bowser or ship.

We also need to tackle the transport issue more seriously. Vehicles, especially those powered by diesel engines, spew out harmful tiny particles that are undoubtedly affecting our health negatively. Diesel has many advantages as a fuel, especially, the fact that engine efficiency is so much higher than that for petrol; however, badly maintained diesel engines are particularly nasty in that they fill the air with black dust that settles very slowly so that it gets inhaled during breathing.

This dust is laden with toxic chemicals most of which have potential for causing serious ill health. This is why we cannot continue tolerating vehicles as they belch black smoke in the lungs of the suffering thousands: nor should enforcement depend on the game of "catch-them-if-three-can" we are currently invited to play while using the streets! Rather, traffic wardens should spend more time booking these offenders and less picking on easier and relatively harmless targets, such as spotting the parked car without its paper clock showing. Cars and trucks pumping black smoke into the air should be regarded for what they really are: disease machines-on-wheels!

But to go back to benzene, which is largely formed as a product of combustion of fuel, including tobacco leaf and wood, but also derives from the evaporation of raw petrol. We recently performed a preliminary study on the personal exposure to this substance of about 50 subjects and found, among other things, that people who spend their lives largely indoors, such as cloistered nuns, are being exposed to the substance to the same degree as university students.

This study is interesting because it seems to suggest that staying indoors in Malta does not really afford serious protection from bad air. We need to conduct a similar study on a much larger number of subjects in order to improve the statistical significance of the data although a first recent attempt at attracting local research funds to the project was unsuccessful.

Your latest study was about dust from quarries, which found alarming levels of dust emission from this industry. Do you plan any follow-up on that?

I plan on continuing with studies on the chemical composition of fine airborne dust in order to establish its provenance: that is, where the dust is coming from. I think that, of all pollutants, fine dust, technically known as PM-10 (Particulate Matter of diameter smaller than 10 micrometres), is the most important to tackle as soon as possible. Even the most recent State of Environment Report acknowledges that airborne dust in Malta is generally above the EU guideline level.

We have a number of possible sources of respirable PM-10 and we are still not sure what the more important contributors are.

Very small black dust, even smaller than 2.5 micrometres (so called PM-2.5) is almost certainly derived from vehicle exhaust, mostly (but not solely) from diesel engines. We have, in our air, dust from quarries and other mineral sources, including transboundary dust that comes from the Sahara as well as seasalt from the Mediterranean. We have no control over some of the sources of dust but that which can be controlled should be controlled.

In regards to the softstone (franka) quarrying industry, I hope that the powers that be realise that there is a problem that has to be tackled. In our research conclusions, we have indicated the principle for a cheap and probably practical solution which could eliminate the problem of dust emission. The scope of the research was not however that of determining how to reduce dust emission in quarrying: I leave that technical problem to be solved by my engineering colleagues.

Rather, my intention was that of sizing up the problem of fine dust produced by this important industry; hitherto, nobody knew how serious the extent of dust emission from quarries was. Now we know and it is expedient on those concerned to consider taking the next steps with a view to eliminate this problem once and for all. This source of fine dust, which we now know is far from negligible, may be the easiest to bring under control without incurring excessive cost; I think a solution is owed to the citizens of this land who share space and air with the quarry owners and operators.

What about other chemicals in the air, from fireworks, for instance?

Renato Camilleri is one of my post-graduate students who is currently trying to establish a link between air quality and the festa season because fireworks manufacture is another industry which I believe has a significant capacity to pollute the air with fine toxic dust, even if it's all done for a good and saintly cause! The work is in hand but it is early days yet to speak of results. Incidentally, I am pleased to be able to tell you that we have received a small financial donation in support of this research from the Church, for which we are very grateful.