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Whilst rare, the impact of a mass disaster can cause devastating loss of life and demolish entire communities -leaving years of reconstruction. Mass disasters can be caused by either environmental destruction such as a volcanic explosion or hurricane, accidental disasters such as aeroplane or train crashes, or by human input- such as terrorism. Two well-known mass disasters are the Asian Tsunami, and the September 11th attacks in New York. Thousands of lives were lost in these tragic events and unfortunately the identification of bodies had many complications as a result of the scale of the impact. Body identification is normally carried out by a Disaster Victim Identification (DVI) team.
The identification of the bodies allows for closure and grievance from all families involved in the disaster, however there are numerous factors and circumstances involved in different mass disaster scenarios that may challenge DNA identification (Alonso et al, 2005). These include: "the number of victims, the mechanisms of body destruction, the extent of body fragmentation, the rate of DNA degradation, the body accessibility for sample collection, or the type of DNA reference samples available" (Alonso et al, 2005).
Recent Mass Disasters
The most recent major terrorist attack occurred on September 11th, 2001 in New York. It was a series of co-ordinated suicide attacks by Al-Qaeda on America. American Airlines Flight 11 crashed into the World Trade Centre's North Tower, United Airlines Flight 175 crashed into the South Tower, whilst another plane targeted the Pentagon and another crashed prematurely in Pennsylvania. A total of 2819 lives were lost as a result of the tragic events (Marchi, 2004).
A recent environmental mass disaster is the Asian Tsunami. On the 26th December 2004, an earthquake with a magnitude of between 9.1 and 9.3 struck off the west coast of Indonesia, triggering a tsunami over 30 metres high which left over 230,000 people dead (Independent, 2010). It was one of the deadliest natural disasters ever recorded, and affected 14 countries, including Indonesia, Sri Lanka, India and Thailand (Independent, 2010).
Other significant mass disasters in recent years include the accidental crashing of Swissair Flight 111. On September 2nd, 1998, whilst on route from New York to Switzerland, when a fire started on board, spreading beyond the control of the crew and resulting in loss of control of the plane, crashing into the sea at Nova Scotia (Independent, 1998). The "Black Sunday" fires in Victoria, Australia, were a series of fires ignited on 7th February 2009, during extreme temperatures of above 40oC (Blau and Briggs, 2010). 173 people died in over 1,100,00 acres of land burnt (Blau and Briggs, 2010).
Challenges in DNA Identification
The usual, initial method of identifying a body is to use visual identification. However, the massive force of the 110 storey twin towers collapsing into a pile of rubble resulted in many of the victim's bodies being charred and pulverised (Marchi, 2004). Biological samples recovered from the site were also subjected to fires of more than 1500oF as a result of the jet fuel from both aeroplanes burning intensely (Butler, 2005). Subsequently, remains were also exposed to masses of water when the fires were distinguished (Holland et al, 2003). Butler (2005) says that this resulted in bodies in this "pressure cooker" being co-mingled, very fragmented and in many cases vaporised. More than "19917 pieces of human remains were collected from a pile of rubble weighing over a million tons and more than 70 feet in height" when then towers collapsed (Butler, 2005).
The initial recovery of victims was also dangerous due to the amount of loose metal debris and fires relighting. The Victorian Fires also had many health and safety issues that had to be dealt with before the scenes could be accessed (Blau and Briggs, 2010). The strength of the remaining walls and floors of the houses needed to be assessed, as well as having to work on floors that were still extremely hot; asbestos contamination was also an issue (Blau and Briggs, 2010).
Dismembered body parts were also an issue after the Asian Tsunami. The sheer force of the waves caused bodies to break up, and the impact of hitting buildings and other stable objects results in disfigurement of the bodies. In accidental disasters, such as the Swissair Flight 111 in 1998 where the plane crashed at sea, remains will be buried miles under water; thus the recovery period is long bone and DNA degradation is high (Butler, 2005). The rate and speed of body recovery from the sea can affect DNA integrity (Alonso et al, 2005). Lessig et al (2006) say that the largest problem for Forensic Examiners at the Asian Tsunami was the advanced stage of decomposition of many of the bodies. Thailand has frequently high temperatures of over 30oC and that combined with the environmental conditions and high humidity led to very fast autolysis (Lessig et al, 2006). "The Indian ocean also had temperatures of 28oC" at that time of year, so bodies were highly decomposed over a short period of time -which could not even be prevented by covering the bodies with large pieces of dry ice (Lessig et al, 2006).
When faced with thousands of pieces of human bone and flesh, Forensic Scientists have to sort the remains into suitable categories. The first is to sort tissue containing bone and non-osseous material, which can be done at the site of impact (Blau and Briggs, 2010). The next is to separate human from non-human material (Blau and Briggs, 2010). Mass disasters not only affect humans, but animals are also killed and as a result non-human bones and tissue are discovered. Also, in attacks such as the World Trade Centre terrorism act, numerous restaurants were destroyed, thus joints of non-human meat will be found in the debris (Blau and Briggs, 2010). Next, the separation of recognisable and non-recognisable tissue fragments that require DNA analysis is made; this was particularly useful in the 2002 Bali bombings from individuals at the epicentre of the bombing as it allowed for quicker identification (Blau and Briggs, 2010). Blau and Briggs (2010) state that following this, the separation of commingled remains should occur, as well as identifying which remains are from the left or right side of a skeleton.
After the Tsunami, an ethnic allocation of bodies was not possible in most cases due to the number of injuries received (Lessig et al, 2006). Thai victims were separated from foreigners by Thai specialists, and were labelled using an electronic chip, and then stored in mass graves (Meyer et al, 2006). These were later exhumed, and in 2005, large refrigerators were installed to stop the bodies from decomposing (Lessig et al, 2006).
A recently developed method that was used for extraction of DNA from World Trade Centre, is the DNA IQe System which "is based on a resin that binds DNA so that inhibitors and impurities can be washed away" (Budowlea, Bieberb and Eisenberg, 2005). It uses "a paramagnetic resin to capture DNA and has a strong denaturing agent that disrupts many types of cells/tissue in preparation for DNA purification" (Budowlea, Bieberb and Eisenberg, 2005). As the sample size decreases, the system efficiency increases as the extraction process minimizes loss of DNA (Budowlea, Bieberb and Eisenberg, 2005). PCR is used to amplify the DNA after extraction as it is useful for the analysis of materials that contain degraded DNA, but this is prior to developing a DNA profile for comparison (Budowlea, Bieberb and Eisenberg, 2005). If PCR is optimized, environmentally contaminated samples can be overcome.
Many of the body parts found at the World Trade Centre were able to be matched to associated remains using DNA profiling (Budowlea, Bieberb and Eisenberg, 2005). However, the severe fires and extreme heat at the collapse of the World Trade Centre resulted in DNA being seriously degraded and thus containing very short DNA template molecules (under 150 bp), making conventional STR matching unsuccessful (Alonso et al, 2005). To overcome this, a new PCR strategy for identifying very short DNA sequences was created. An example of this is the "development of Mini-STR multiplexes based on redesigned primers to obtain shorter amplicons" (Butler, Shen and McCord, 2003). This increased the success rate of obtaining STR typing results from a proportion of remains (Coble and Butler, 2005). Another example is the "Mitochondrial DNA sequencing of hyper-variable regions 1 and 2 (HV1 and HV2) used to obtain complementary DNA data from World Trade Centre remains (Bieschke et al, 2004). Holland et al (2003) also created the extraction of DNA from bone as a result of the World Trade Centre disaster. This occurred in two phases - the implementation of traditional DNA extraction methods redesigned to cope with high throughput and protocol changes to improve DNA yield (Bille et al, 2004). "The copy number of mitochondrial DNA molecules in a cell is in the thousands compared with only two copies of each chromosome in the nucleus"(Budowlea, Bieberb and Eisenberg, 2005). Mitochondrial DNA has a circular nature, and thus it may protect it from degradation (Budowlea, Bieberb and Eisenberg, 2005). Budowlea, Bieberb and Eisenberg, 2005 also state that if "the amount of extracted DNA is very small or degraded; it is more likely that a DNA typing result can be obtained by typing mitochondrial DNA than by typing STR loci."
STR multilocus matching is another simple and effective method that was used in DNA identification at the Twin Towers, as it allowed the matching of a victim's DNA profile to a personal item such as a toothbrush (Alonso et al, 2005). However, the amount of debris at mass disasters causes problems as DNA derived from tissue fragments is often contaminated with inorganic building material, causing mixed DNA profiles. Budowlea, Bieberb and Eisenberg, (2005) say that the "quality of samples obtained from mass disasters will vary substantially, from apparently pristine to highly degraded to substantially contaminated (con-mingled with tissues form other victims or containing materials that may inhibit portions of the analytical process)". Often, in cases such as the Twin Towers attacks, people will be carrying their personal items, such as toothbrush and hairbrush, with them so these are likely to have been destroyed in the disaster (Butler, 2005). In some situations, such direct DNA comparisons are not possible, so kinship analysis is used by providing reference samples from family members (Budowlea, Bieberb and Eisenberg, 2005). Family members may not, however, abide with this, as giving DNA to the police may make them feel like a suspect, rather than just assisting the investigation.
New developments to overcome challenges in DNA identification include the creation of a system for "bar-coded based soft tissue collection and simultaneous body tracking" allows long term DNA preservation under desiccation conditions (Alonso et al, 2005). This is beneficial as it allows numerous specimens to be collected for DNA analysis and be simultaneously labelled using barcodes (Grassberger et al, 2005). Grassberger et al (2005) also state that barcode technology "enhances the rate and accuracy at which information can be collected and eliminated the opportunity for error".
The need for rapid, large-scale DNA sample analysis after a mass disaster is another challenge. Automation and robotic implementation of some steps of the DNA analysis procedure have been applied after the World Trade Centre attacks to lower the costs and increase the turnaround time for DNA analysis of victim and reference samples (Alonso et al, 2005).
A challenge faced in a mass disaster such as the Asian Tsunami is that a high number of deceased relatives is expected to be found, as well as entire families dying without leaving any family reference for comparison- due to families sheltering together (Alonso et al, 2005). Personal items will also be destroyed, again reducing the availability of comparisons. Another complication is the locating of surviving family members, especially after the Asian Tsunami as bodies may have washed up in areas miles away from their home, and many of the communities are very small; resulting in communication issues (Butler, 2005). Another issue is relationships- for example families arguing over who has the right to own the remains, and DNA testing showing that someone is/is not the father of a child-so care must be taken to ensure information is delivered sensitively (Butler, 2005). Furthermore, the larger number of deaths in a community results in the larger the problem of distinguishing the true from false relatives (Brenner and Weir, 2003). As the number of victims increases the number of victims who "coincidentally bear only a modest genetic similarity to their kin references" increases, the likelihood threshold decreases (Brenner and Weir, 2003).
The vast area of land that mass disasters cover is a challenge, as DVI staff are limited and can only process an area at a time to prevent contamination. In the case of the 2009 Victorian Bush fires, there were 145 different scenes, spread over an area of 4000 hectares (Blau and Briggs, 2010). Most of these sites burned for 4-5 days and as there were allegations that some fires had been intentionally lit, all sites were treated at crime scenes (Blau and Briggs, 2010). This dramatically slowed the identification of victims. However, in cases such as bush fires, communities are often given a little warning about an impact, and are advised to leave the area or shelter in appropriate places. Consequently, many bodies recovered from the bush fires still had relatively intact skeletal elements such as "vertebrae, heads of radii, articular surfaces of proximal aspects of femora and tibiae, as well as patella and tali" (Blau and Briggs, 2010). Bone endings such as that of the femur are the most expected to survive fire damage as it is deeply located within a large muscle mass (Blau and Briggs, 2010).
A side effect of dealing with DNA identification of mass disasters is the affect on Disaster Victim Identification staff. The psychological affect of seeing many dismembered and badly damaged human remains, along with the possibility that family members could be amongst the dead (in the case of natural disasters) will put strain on the workers, which is another challenge facing DNA identification (Butler, 2005).
To conclude, the development of new techniques such as Mini-STR analysis and extracting DNA from bones has allowed previously unidentifiable remains to be matched successfully. Unfortunately, the dramatic impact that mass disasters have on communities means that all victims of the disaster will never be accounted for, but research has shown that using a strict strategy and modern methods of identification, the challenges a Forensic Scientist faces can be depressed.
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