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Diesel Particulate Filter

As already reported, most solid, inorganic particulate matter produced by human activities is not degradable. The immediate consequence is that, as already mentioned, however little dust enters the environment, it will inevitably add to what is already present In short, particles continue to accumulate.

Numerous sources of particulate matter are responsible for the situation, starting, as we already mentioned, from those of natural origin: volcanoes, rock and soil erosion, sand and forest fires, among others. On these causes it is actually impossible to intervene and take effective action. A different matter, however, is what regards the numerous anthropic sources: power plants operating with heavy oils and coal-fired biomass plants, domestic heating, waste incinerators, car traffic, etc. And car traffic is by far the easiest target.


Figure 3.10 (a) Sample of a bee's body, contaminated. Particles expelled from the factory chimney were found on the whole body of the bees raised in the area surrounding the cement factory for a radius of a few kilometres, (b) Vine leaf contaminated. Particles fallen from the chimney of the cement factory containing those elements were found on the leaves of the vines and on the grapes collected within a radius of a few kilometres around the cement factory, (c) Cement. The images refer to a sample of Portland cement produced in an area where a type of grape is grown to produce a fine wine. Elements such as copper and zinc come from waste, which is treated at high temperature to be mixed with the finished product.

Diesel engines, in particular, produce considerable amounts of carbon particulate, and this is the cause of both strictly environmental and health problems.

In all advanced countries, there are maximum limits allowed for particle pollution (PM10 or PM2.5), and reaching and exceeding those limits is indicated by control units. What those control units do is weigh the amount of particles in relation to what is contained in a normal cubic metre (Nm3) of air, that is, that volume of air measured under the standard conditions of 0°C and 1 atm of pressure. Diesel engines (but all internal combustion engines behave in the same way independently of the fuel) emit relatively coarse carbon particles, and once in the atmosphere, these are regularly weighed by the control units. So, to not incur penalties, it is expedient to make sure that the control units detect a weight which is as small as possible.

The simplest way to do this is to burn the carbonaceous particles so as to transform them into gases which, obviously, preserve the mass but which, on earth, do not have a weight, that is, a value detectable by a scale. In this way the control units, in fact scales, will not detect anything.

This is what a diesel particulate filter (DPF) does, burning the particles captured inside a device located along the exhaust pipe downstream of the engine (Fig. 3.11).

Leaving aside the obvious conservation of mass, that is, something which does not depend on human will, the major problem is that of the content of the captured particles. They are made of carbonaceous material, but each of them contains smaller particles of metallic nature derived from the friction of the mechanical parts (piston and cylinder) and from the additives which are components of fuels and lubricants. Those metal particles cannot be burned, are emitted into the atmosphere and are preserved as such wherever they end up. Being contained in the coarse carbon-based particle, they are obviously smaller and more numerous than their original containers and, therefore, they are more aggressive towards health than are the untreated emissions.

DPF. The filaments seen in the electron microscopy images are those of the filter on which the exhaust gases of an automobile equipped with a DPF were collected for our analysis

Figure 3.11 DPF. The filaments seen in the electron microscopy images are those of the filter on which the exhaust gases of an automobile equipped with a DPF were collected for our analysis. The numerous particles captured by our filter would not have been freed from their carbon matrix into the environment if the anti-particulate device had not burned it, turning it into carbon oxides. As often mentioned, the spherical shape is characteristic of high-temperature formation. In the image at higher magnification it can be seen how part of the carbonaceous matrix (grey and formless around the particles) remains unburned.

In the book Nanopathology: The Health Impact of Nanoparticles (Pan Stanford Publishing 2008, now Jenny Stanford Publishing, page 212), we showed that the filters we checked emitted in the environment cerium dioxide used in the system and nanoparticles of platinum present as a catalytic converter. It should be added that while some DPFs use cerium dioxide to trigger the combustion of carbon particles at a relatively low temperature, others use ferrocene, an organo-metallic compound consisting of two cyclopentadienylrings linked on opposite sides of a central iron atom, which cannot fail to enter the atmosphere - two substances whose toxicity has never been thoroughly studied and which would certainly not have been released into the atmosphere without the use of those systems. In conclusion, the DPF system is presented as a technical means to avoid pollution so much that it has become mandatory in diesel vehicles but which, in fact, like it or not, is a producer of aggressive particles.

War and Terrorism

There can be no doubt: war is made to kill or, in any case, to cause damage to the enemy. It is not always certain, however, that those damages, so desired and achieved by expenditure of energy and money as they are, are made only to those against whom a war is being fought.

When, centuries ago, the armies began to use explosives, the inevitable side effect was that of generating clouds of dust, and dust is never beneficial, no matter by which side it is produced.

Over time, as happens with industrial technologies, also in warfare combustion, temperatures keep growing higher and higher, and as we already know, the higher they are, the finer the dust generated is, with all its consequences on the environment and on people's health.

Modern wars pollute the environment like never before with wars of the past, and many examples could be made.

It is normal for civilian settlements to be destroyed and at least partially reduced to dust, but strategic objectives are the favourite targets, many of which are polluting establishments as such. Bombs against strategic targets such as weapons factories, chemical factories or power plants lead to a very particular increase of the pollution of the area, pollution which, generally, is not monitored if not, and certainly not always, at the end of the war, but which continues to exist often for a long time when peace has been restored and which, because of the mobility of pollutants, can also involve neighbouring countries which had not been part in the conflict.

In 1999, the Pancevo (Serbia) refinery was bombed for three consecutive days. Aside from the civilians who died immediately, the tanks of unrefined oil went to fire and produced a tall column of toxic fumes. As the cloud carried by the wind was heading towards the US base, the American planes took off and scattered silver iodide particles to cause rain according to a well-known technique. The rain, rich in silver iodide particles mixed with the soot produced by the combustion of the oil, a soot containing bromide-chlorine-lead particles, contaminated the pastures and the river Danube, which flows into the Black Sea.

The extent of such damage is very difficult to assess, but to be sure, as often happens in similar cases, there is not even the will to do it.

Figure 3.12 shows an example of a post-mortem finding of nanoparticles (10 nm) dispersed in the lymph nodes of an inhabitant of Pancevo who died of lymphoma in the university hospital of Sarajevo. The soot of the combustion of the unrefined oil was detected in his corpse.

It must be remembered that in the course of the fighting involving Kuwait and Iraq, several oil wells were set on fire, becoming for a time enormous sources of pollution with all the consequences of the case.

And other pollution, albeit of lesser proportions and with consequences almost only to the detriment of the soldiers closely involved, was due to the destruction of weapons captured by the enemy, making them explode.

It is not at all surprising that after the end of the conflicts, cancer pathologies began to appear with a particularly high frequency with civilians, while the first victims were the soldiers. The longer-term consequences, however, are borne by the inhabitants of the areas involved, where pollution is inevitably destined to remain for a time which is hard to predict but, in any case, will be very long and will also affect generations to come. It is a fact that the observatory founded in Sarajevo after the end of the Balkan War continues today to record an increase in cancer cases which would have been unexpected if the conflict had not existed. As is obvious, cancer and other pathologies related to war pollution do not spare those who have fled the conflict zones, and therefore, one can die of war even far in space and time from it

Of the pathologies linked to the wars fought in the Persian Gulf and in the Balkans, there is no exhaustive news, because not a little has been kept hidden and continues to be so. For example, little or nothing is known about what happened to many soldiers of the NATO forces.

War lymphoma case from Pancevo

Figure 3.12 War lymphoma case from Pancevo. Lymphoma is a form of cancer we have come across most often by analysing pathological findings of both soldiers and non-military subjects active in the territories where a war was being fought or had been fought in the past and of inhabitants of those areas. In war environments, the concentration of particles can be very high, and it happens that large quantities of dust enter the body quickly and repeatedly. Macrophages intervene massively before the particles are enveloped by granulation tissue and move them to the lymph nodes where, being non-biodegradable and impossible to eliminate, they remain and give rise to cancer of the lymphatic system. Typically, cancer needs a long-enough time to manifest itself, and therefore, many cases have become evident after the war had ended for years. The fact must also be considered that the non-degradability of the particles and, therefore, their remaining unchanged in the environment extend their pathogenicity for a long time. The elemental analysis highlights the complex composition of the particles of war origin, a composition which is not found in 'normal' urban pollution and which is due to high-temperature explosions involving the most disparate materials.

Apparently, the Gulf Wars have affected American and British soldiers the most, while those of the Balkans seem to have affected Italians more, although thereare certainly cases ofother nationalities.

The pathologies look quite similar, although it seems that the American soldiers have suffered from neurological problems with psychiatric implications much more than has happened to the Italian soldiers with whom we have dealt most.

Some explanations for these differences could be sought in the fact that in the wars fought in the Persian Gulf numerous oil wells were set on fire and a large amount of armaments, perhaps even chemical in nature, were destroyed by making them explode so as not to have to bring them to the United States.

It is also necessary to take into account the medicaments, some of which lacking adequate testing and, in any case, without any authorisation to trade, taken by US soldiers (or, maybe, of other nationalities?) to prevent possible attacks by chemical weapons carried out by the enemy army. Of those drugs, their side effects and their mutual interactions, there is not enough information to express any judgment. Often there is no information at all.

Terrorism, particularly modern one, is much subtler than traditional war and, in a way, is harder to understand and to face, as it follows a logic which is at least partially different from what is ‘reasonable’ and definitely unusual. But, regardless of considerations which can't be part of this discussion, there are instances, as was the case of the attack on the Twin Towers in New York, where the medium- and long-term consequences from the health point of view are absolutely similar.

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