**11. Dioxin**

Dioxin is a specific organic unsaturated non-antiaromatic six-membered ring compound with a chemical formula of C4H4O2. However, the term dioxin is used generically by most authorities to include chlorinated dioxins with furans and many derivative compounds as a complex of at least 75 ubiquitous and environmentally persistent organochlorine compounds, of variable toxicity.

The incomplete burning of sea water impregnated coastal peat in Scotland well before the industrial revolution has recently been shown to produce dioxins.9

Soil containing unburnt peat was taken both from the surface of the St Kilda arable area and excavated from houses down to the time strata of 1800–1850, has been found to contain 114 ng/kg of dioxin. Cultures for the tetanus bacillus at this depth would have been fascinating to ascertain the presence or absence of this micro-organism. Burning peat produced 643 ng/kg of dioxin in the peat smoke and ash. This would give a total dioxin production by the estimated 260,000–420,000 inhabitants of the Scottish highlands and islands in the eighteenth and nineteenth centuries of 1 kg/year, about one fifth of that produced by the whole of the UK in the industrial era.

St Kildans stored peat ash mixed with cow manure on the house floors over winter and in spring fertilised the island's arable land with the mixture, such that more than 70 years after the evacuation there are still high levels of TCDD in the arable area. 11

The mammalian immune system has been shown to be susceptible to direct damage by low doses of dioxin, and indirectly by damage to the immuno-modulating effect of the hormonal system. Animal studies have also shown that dioxin toxicity can cause thymic involution, decreased antibody production with thymic dependent and independent antigens reduced function of the HLA system producing some lymphocyte subsets and reduced cytotoxic Tcell function.

The question therefore arises if the dioxin pollution was a contributory factor to the infections experienced by the inhabitants of St Kilda. Comparison with the major known leak of the dioxin, TCDD (2,3,7,8-Tetrachlorodibenzo-p-Dioxin) from Seveso near Milan in 1976, suggests this is unlikely. The soil levels of dioxin in Italy were considerably higher, yet careful follow up over many years in Seveso found no acute increase in the incidence of acute infections, but there was an increase in carcinomas of the gastrointestinal tract and lymphatic systems and an increase in the death rate from respiratory disease. Dioxins are believed to be carcinogenic, but cancers were not a common problem on St Kilda.

Fig. 15. Chloracne

236 Biodiversity Loss in a Changing Planet

Macaulay noted that once this epidemic had resolved it did not recur without further visitors. Three episodes were once noted to occur within eight weeks following three separate visits from other islands, making the usual suggestion of influenza unlikely, as this

Human rhinoviruses (HRV), with 110 serological types, are the most common worldwide infective viral agents in humans, causing 30–50% of all cases of upper respiratory infection based on viral cultures, or an even higher percentage using improved detection techniques including reverse transcription-PCR. The short incubation period and recurrent infections with severe cough and profuse sputum, plus some cases of pneumonia and rare deaths, strongly support rhinovirus as the cause of the boat cough. Although adults with an averagely robust immune system usually experience one brief episode per year, the prolonged and recurrent bouts experienced by the St Kildans again support some problem

Unfortunately departure from the island to places of opportunities, a better climate and

In 1852, thirty-six of the islanders migrated to Australia. Although they were among the youngest and fittest from the community, they suffered a 50% mortality on the voyage to Melbourne, mainly from measles. In the years immediately after the final evacuation in 1930, several of the young children died of tuberculosis. In these two examples, the factors of poor climate, malnutrition and isolation no longer applied as much, but the factors of low herd immunity and limited biodiversity were the main causes of death and disease in these

Dioxin is a specific organic unsaturated non-antiaromatic six-membered ring compound with a chemical formula of C4H4O2. However, the term dioxin is used generically by most authorities to include chlorinated dioxins with furans and many derivative compounds as a complex of at least 75 ubiquitous and environmentally persistent organochlorine

The incomplete burning of sea water impregnated coastal peat in Scotland well before the

Soil containing unburnt peat was taken both from the surface of the St Kilda arable area and excavated from houses down to the time strata of 1800–1850, has been found to contain 114 ng/kg of dioxin. Cultures for the tetanus bacillus at this depth would have been fascinating to ascertain the presence or absence of this micro-organism. Burning peat produced 643 ng/kg of dioxin in the peat smoke and ash. This would give a total dioxin production by the estimated 260,000–420,000 inhabitants of the Scottish highlands and islands in the eighteenth and nineteenth centuries of 1 kg/year, about one fifth of that produced by the whole of the

St Kildans stored peat ash mixed with cow manure on the house floors over winter and in spring fertilised the island's arable land with the mixture, such that more than 70 years after

The mammalian immune system has been shown to be susceptible to direct damage by low doses of dioxin, and indirectly by damage to the immuno-modulating effect of the hormonal

organism does not mutate into a new infecting subtypes as quickly as this.

greater development failed to protect the people of St Kilda.

industrial revolution has recently been shown to produce dioxins.9

the evacuation there are still high levels of TCDD in the arable area. 11

in their immune systems. 10

**10. Migration** 

migrants.

**11. Dioxin** 

compounds, of variable toxicity.

UK in the industrial era.

Chloracne, an acne-like skin eruption, most marked behind the ears, on the cheeks and in the axilla and groin, affected a significant number of Seveso's inhabitants ( 42 of 214 children in the most contaminated Zone A.) Viktor Yushchenko, past President of the Ukraine, is considered to suffer from this condition, following an acute illness in 2004 in which his face became disfigured, scarred and pockmarked. Levels of dioxin in his blood were reported to be 6,000 times above the safe minimum, but the veracity of these tests are debated by toxicologists, and the possibility of deliberate poisoning is debated in political circles. Chloracne has become the '*sine qua non'* of dioxin poisoning.

Another dioxin leak, probably with TCDD, occurred Germany in 1953. Again chloracne occurred, and acute respiratory tract infections were more common only in the group with severe chloracne. Photographs on the St Kilda population from the late 19th century show no evidence of chloracne in the women and children. Although the men have heavy beards, there is no visible evidence on photographs of chloracne around the neck, nor reports suggesting this dermatological disease. Dioxin toxicity on St Kilda appears a most improbably contributory factor to the infections suffered by the islanders

Limited Bio-Diversity and Other Defects of

wrote in 1882 that 'sickness is almost unknown'.

guaranteed the survival of the Pacific island society.

a thriving tourism business.

**13. Conclusion** 

the failure of the other.

the Immune System in the Inhabitants of the Islands of St Kilda, Scotland 239

Both islands are remote even today. Although the distance from Glasgow to St Kilda (main island, Hirte) is only some 340 km as the crow flies, it can take three or four days to get there using sea, land and air transport, including a landing on the 'airstrip' at Barra –the beach at low tide. The journey from Brisbane to Lord Howe Island, a distance of 740 km, in the past took several days by sea, but now a return flight is possible in one day. Both islands are small and have sheer cliffs and high rainfall. Both have UNESCO World Heritage status in which ornithological significance plays a large part, an abundant supply of fish in the surrounding sea and a nearby sea stack renowned for unique bird life. The difference in latitude and ambient temperature were significant factors in the success of one society and

The earliest settlers on Lord Howe Island had widespread genetic origins, coming from England, Portugal, America, South Africa, Micronesia, New Zealand and Australia, probably with a much greater biodiversity of histo-compatibility antigens creating more resistance to infections than that of the Hebridean people of St Kilda. One of the early settlers, Nathan Chase Thompson, from Somerset, Massachusetts, in the USA, arrived in 1853 with two business partners, George Campbell and Jack Brian, and two women and a girl from the Gilbert Islands (now Kiribati). Thompson initially married Boranga, one of the women, but their only child died aged 11 years and Boranga died soon after. Thompson subsequently married the Gilbertese girl, Bokue, who was by then aged 24. They had five children, two boys

and three girls, whose descendants are an important part of today's island population.

Supporting evidence comes from an epidemic of measles, a disease with a mortality of up to 25% in the developing world. In 1868, some inhabitants of the Pitcairn Islands visited Lord Howe Island in the schooner *Pacific* while suffering an outbreak of measles. They landed and recovered on the island, causing an inevitable outbreak of the disease among the islanders. No more details are available, but no deaths in 1868 are to be discovered in the island records or graveyards, implying that poor herd immunity allowed the outbreak of measles but the genetic and environmental background resulted in uneventful recovery. In contrast to St Kilda, Lord Howe Island appears a paradise of good health and longevity. Regular visits by whalers in the early years of settlement would have helped to reduce isolation and perhaps improve the herd immunity. William Clarson, a visiting teacher,

A visit to the four island graveyards shows that most inhabitants born more than 100 years ago survived into their 80s, and today Lord Howe Island has 347 permanent residents, with

Medical factors played a major role in the success of Lord Howe Island and the failure of St Kilda. Appendicitis became a manageable problem on Lord Howe Island, with recorded surgery on kitchen tables, but was a final straw leading to the evacuation of St Kilda, when two weeks passed before Mary Gillies with acute appendicitis could be notified and transported to a Glasgow hospital where she died within twenty-four hours. The climate and virgin soil allowed the Pacific islanders a much more beneficial varied diet with food rich in vitamin C. This fact plus the biodiversity of the early settlers and their improved obstetric care protected the young children of Lord Howe Island from infections and

The inhabitants of St Kilda were an inbred population with limited genetic diversity. They suffered severely from infectious diseases, more than similar inhabitants of nearby islands,
