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The Case of the World Trade Center

On 18 September 2001, a week after the attacks to the Twin Towers and the Pentagon, Christie Whitman, administrator of the US Environmental Protection Agency (EPA) announced that air and drinking water had been monitored both in New York and in

Washington and they were ‘safe’, adding, ‘We are very encouraged that the results from our monitoring of air quality and drinking water conditions in both New York and near the Pentagon show that the public in these areas is not being exposed to excessive levels of asbestos or other harmful substances.' The document continues describing briefly how the monitoring had been carried out and what clean-up measures had been adopted [4, 5].

Almost a couple of decades later, the extent of the disaster is not yet clear, but it involves in a chronic way the heath of many hundreds of thousands of people who inhaled and ingested the fine and ultrafine dust created by the collapse the two aircraft aerosolised and the very high temperature of the phenomenon. In early 2020, at the time of writing these pages, three more firefighters, who began to get sick after six months of working at Ground Zero, died of the cancer they had started to develop after their exposure to the dust.

Among the enormous variety of materials contained in the two aircraft and in the two buildings there were huge quantities of asbestos, and those mineral nanofibres were transformed by the heat into something even smaller and, therefore, more penetrating. Generally, mesothelioma, the typical asbestos-induced cancer, takes a long time, often decades, to become clinically visible. Yet, some people who were involved in the disaster have already died of it.

Unfortunately, but, from a certain point of view, understandably, a lot of people flocked to the disaster site immediately after its occurrence: firefighters, the police and health rescuers, trying to do something to rescue non-existing survivors. But there were also journalists, photographers, medical staff and common people curious to see what had happened. Many, in particular firefighters and the police, returned for months to Ground Zero. All of them, regardless of their job and the reason why they were there, submitted themselves to a huge risk. But that dust spread over a very large area, and even those who had not approached the scene of the disaster but, however, lived in the New York area were inevitably affected [5].

So, 9/11, whoever those responsible were, was the first terrorist attack on a massive scale and was much more successful in terms of damage inflicted than the perpetrators themselves had expected.

We had the possibility to analyse the dust deposited on the work uniform of a firefighter, a dusty object taken from a shop which was located inside the Twin Towers and the sweat of some firefighters who underwent a special treatment of decontamination one year after their contamination.

(a) Firefighter's sweat,

Figure 3.15 (a) Firefighter's sweat, (b) Firefighter's sweat contamination. The electron microscopy photographs (a and b) show some particles detected in the sweat, dark in colour, of firefighters who worked immediately afterthe collapse of the Twin Towers in New York in what is now called Ground Zero. The sweat collection was carried out four years after the exposure of the subjects and still contained evident traces of the dust which could have been breathed and swallowed and that the organism, it is not known how effectively, was expelling through the sweat. The detected particles are similar to those found on objects and clothing which were hit by the dust caused by the collapse. It is not possible (Continued)

to determine, however, whether the particles found in the analyses shown in the images actually date back to what entered the body of the firefighters while they were working in 2011 or if, instead, they are particles still present in New York which entered the body later, in a moment temporally close to that of the production of sweat. The composition of those particles is extremely varied and complex, and this is due to the complexity of the structure and content of the collapsed buildings and the two aircraft which were reduced to dust of all sizes, (c) Sweat of a female patient suffering from a pathology which was never clearly diagnosed but who was contaminated by particulate matter contained particles as well.

The sweat contained some particles whose chemical composition could be related to the dust originated by the event In our already quoted book Nanopathology (page 255), there are some examples of particulate matter identified. The composition is unusual and does not correspond to any known material: for example, particles of gold alloyed with zinc and tin were identified in the sweat, and they were also incorporated in the fatty tissue. A possible explanation was that inside the Twin Towers there were vaults of banks hosting gold bars which were melted by the heat, along with other metals, thus forming odd particulate which was immediately dispersed in the environment (Fig. 3.15).

Engineered Nanoparticles and Nanotechnologies

Unlike the great majority of particles, only some of them, but increasingly, are expressly manufactured in specialised laboratories.

Their synthesis can take place in two different ways, called top-down and bottom-up.

Top-down synthesis starts horn bulk material whose size is progressively reduced by attrition or milling. In the bottom-up approach, the particles are made by self-assembly as happens, for instance, with chemical synthesis [6].

Actually, particles are not only an undesirable side effect: when they are designed and manufactured in a targeted manner by a specialised laboratory, they are something of whose extraordinary properties, unexpected until a few decades ago, interesting technical and financial advantage can be taken. In fact, the investments in this field are huge and on the increase.

Nanoparticles have unique physical and chemical properties which, in many respects, are very different from those of the same compositions in the bulk. At the nanoscale, materials behave very differently compared to the same materials at larger scales and it is not easy to predict with sufficient accuracy those properties when applied to a single particle. Colour may change (in function of their size), and so electrical conductance, wettability and many other properties. As a matter of fact, the chemical processes taking place on the surfaces of nanoparticles are very complicated and, for the time being, remain largely unknown. Only with direct experience can reliable information be obtained. Which, moreover, is valid for all science proper.

All that has been briefly explained so far must be considered when it comes to evaluating the action of nanoparticles within biological tissues. Too little is known about this, and often even the little which is known is overlooked.

The phenomena making nanoparticles different from the bulk version of the same material are mainly based on ‘quantum effects' and the high ratio between surface and volume. Nanoscale materials have a much larger surface area than an equal mass of larger-scale material, and as surface area per mass of a material grows larger, a greater amount of it can come into contact with the surrounding matter, that way increasing reactivity. Most biological processes occur at the nanoscale, and their observation gives scientists and technologists models and templates to imagine and construct new processes which find application in medicine, imaging, computing, printing, chemistry (chemical catalysis in particular or, to be more accurate, the supply of energy necessary to have a certain reaction occur, which is not catalysis proper), synthesis of new materials and many other applications in what is called nanotechnology.

It is necessary to know that all laboratory processes related to the production of nanoparticles are potentially risky for operators. In fact, they can come into continuous contact with the particles, and therefore, it is advisable to work in suitable environmental conditions, including positive pressure.

A practical problem which is not always easy to solve when working with nanoparticles is their strong tendency to attract each other.

The mutual attraction can determine two different situations: one called clustering, in which the particles joined together can be separated through an ultrasound treatment, and the other called aggregation, where the situation is irreversible and it is no longer possible to return to the starting point, that is, of single particles.

So, engineered nanoparticles are very hard to handle, and among other technical problems, this makes it difficult to carry out biological experiments, particularly in vivo ones, as the investigators think they are administering nanoparticles to their subject (generally cells or an animal), while what they actually deal with are much larger entities, and those larger entities produce results which cannot be those of nanoparticles, the volume of which differs by several orders of magnitude. Therefore, it can happen that some results reported in the literature as due to nanoparticles are actually those of microparticles.

A further problem is the ease with which different metal nanoparticles tend to ignite when handled at room temperature and in a normal air atmosphere due to their high surface-to-volume ratio and, as a consequence, their great energy.

Engineered particles are at the base of nanotechnologies, that is, one of the biggest financial investments in the history of economy. If it is true that particles give very advantageous properties to the products, it is equally true that, as is almost normally the case in industry, the entire life cycle of the object which is being designed or actually manufactured is too rarely taken into due consideration. In this case, the first safety problem to be addressed is that relating to production conditions, and then comes the contact of the product with the user. But the main problem is how to dispose of the product once, whatever the reason, it is no longer needed. Although not always, in most cases, the particles used are almost indestructible, and in one way or another, they will end up in the environment, where they will accumulate with those already present

Nowadays they are used to make new products now commercially available, like clothes, paints, computer and telephone parts, pesticides, deodorants, drugs, etc., growing more and more popular. Nevertheless, it should be clarified that to date, the quantity of the engineered nanoparticles presenton earth is far smaller than that of the particles of natural origin and those of unintentional anthropic origin. Still, they are growing contributors to pollution.

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