Dust is an all too familiar topic at the end of a hot dry summer. Dust particles, or soot if it comes from combustion, is more than just a nuisance. This particulate matter (PM as scientists call it) can cause the air to appear hazy when present at high levels.

A freak rainstorm brings temporary relief as paved areas are washed clean of dust from construction sites, quarrying, sandblasting and from the wearing down of tyres and brakes on our roads.

Other particles suspended in the air might be due to certain weather conditions, as when there is sea salt spray or fine dust blown from the Sahara desert. These are considered as coming from natural sources and are deducted before the authorities arrive at a national figure for dust to submit, along with other environmental data, to the European Commission.

As one would expect in Malta, from time to time, set limits have been exceeded when the level of recorded dust particles, even with natural sources excluded, goes beyond the red line.

Dust comes in three measurable sizes: small, medium and large. Fine dust particles of PM 2.5 are a quarter of the size of the larger PM 10 particle and generally more harmful to our health. At just one tenth of the size, ultrafine PM 0.1 particles can cross from the lungs into the blood, bringing even more health problems.

Earlier this year, the European Commission’s science for environment policy briefing put out an alert on the risks of exposure to fine particles during pregnancy in relation to Autism Spectrum Disorder (ASD) in children.

Recent studies suggest that the chances of a child developing ASD are higher if the mother is exposed to high levels of fine particulate air pollution during pregnancy, a recent study suggests.

Although genes play a part, researchers have found that a mother’s exposure to air pollution during pregnancy may increase the risk of her child developing the condition. It is the medium-sized PM 2.5 particles which appear to interfere most with the unborn child’s brain development when exposure to high levels occurs in the final three months of pregnancy.

Sand blasting in dockyards produces large and medium-sized particles of fine dust. The high breakdown rate of sand results in substantial dust generation and workers without proper equipment can suffer from silicosis, which can lead to death. Synthetic abrasives, such as silicon carbide and aluminum oxide, are becoming popular substitutes for sand as they create less dust.

A medical study of children with ASD, if conducted in areas surrounding the dockyard and port, might provide useful information on local environmental risks.

Combustion of fuel by road, sea and air traffic or by power stations is the main contributor to high levels of particulate matter.

It is true that shipping is the most efficient way to transport freight on a tonne per kilometre basis. Despite this, ships still produce a significant amount of emissions which can create environmental problems, especially in the vicinity of ports. Ship engine emissions are being taken into account with regard to lung and cardiovascular diseases in coastal regions worldwide.

Over 2,500 tons of the air pollutants nitrogen oxides, sulphur dioxide and fine particulate matter were released by cruise ships across the five busiest Greek cruise ports, according to a 2013 study. The industry has experienced rapid growth in recent years. Cruise ships are one of the most energy-intensive tourism activities, bringing a boost to the economy, yet the cost of health impacts is also high.

Diesel fuel (DF) is known as the ‘clean’ shipping fuel. Yet the effect of DF particles on the respiratory system has been noted to be stronger than that caused by particles from heavy fuel oil, possibly due to the higher soot content of diesel.

A study published earlier this year in the US-based Public Library of Science open access journal (PLOS one) recommended a reduction of soot in ship emissions through the use of filters.

Civil society is not generally known for putting pressure on the maritime transport industry to reduce its emissions as commercial ships are usually far from the public eye. In Europe, the shipping sector has slipped through the net of carbon dioxide emissions regulation. Its first CO2 targets will not come into force until 2018.

The Mediterranean is one of the world’s busiest waterways, accounting for at least 25 per cent of global shipping. Off the coast, to the north of Gozo, ships of all sizes steam day and night through the bottleneck of the Sicilian channel. Prevailing winds blow their emissions towards us for much of the year.

When two or three 50,000-tonne ships go by in one night, it is the equivalent of having an entire power station floating past us, with all the emissions that entails.

Some of the smaller ships may be cargo vessels stopping at the Freeport which has plans to expand its container capacity and increase traffic. Others are cruise liners – over 300 called at Malta and Gozo last year, with numbers expected to increase in coming years.

Watering and powering up these behemoths whenever they drop anchor is a huge undertaking. Many docked ships use their engines to produce electricity. However, some ships are equipped to use shore power, taking their electricity from the power station. Malta’s national greenhouse gas inventory includes emissions from cruise ships visiting port but there is no available data on particulate emissions from the liners that grace the Grand Harbour.

A cruise ship report card put out annually by Friends of the Earth International received criticism from the industry on a debatable technical point.

Last January, UK newspaper The Guardian picked up the story, reporting on a number of cruise companies, some of which operate in Malta.

Norwegian Cruise Lines received top grades in water quality and sewage treatment, but a D in air pollution reduction. A well-known Italian cruise company was graded F for air both pollution reduction and the quality of sewage treatment on its ships.

Emission control areas (ECAs) for shipping have been put in place by the International Maritime Organisation as recently as last year for Caribbean cruise routes. However the Mediterranean seems to have been sidelined.

Although some lesser controls apply to non-ECAs, we are still lacking the best available controls for air emissions under the International Convention for the Prevention of Pollution from Ships (Marpol). Mandatory requirements for the Mediterranean Sea, related to oil spills and dumping of garbage, were brought in under Annex 1 and Annex 5 as far back as 1973.

Annex 4 for prevention of air pollution from ships has been in force since 2011 for the US and parts of the Canadian coastline, six years after it became active in the Baltic and North Seas. Caps on sulphur content of fuel oil as a measure to control sulphur dioxide emissions indirectly reduces particulate emissions. Nitrous oxide emissions from shipping are to be further reduced by 2016 and restricted to 2011 levels for non-ECA areas.

From 2018, monitoring of carbon dioxide emissions from large ships using EU ports will come into force, however there appears to be a commercial interest waiver option where particulates are concerned.

Aviation authorities are aware that PM emissions are featuring more in discussions on the environmental effects of aircraft in communities near airports. A standard for measuring particulate matter from aviation has been under development since 2010. Soot is the main component of jet engine exhaust, however it has not been easy to reliably estimate particulate matter from airplanes.


Source: Times of Malta

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