Pollution is not a word commonly associated with the Hebrides. Certainly not when I mention that I'm referring to St Kilda. It would appear that pollution was one of the factors that led to the demise of that community. Strange, but true.
The two main pollutants were heavy metals and dioxins. Heavy metals are present in fatty deposits in seabirds. The elements concerned are zinc, cadmium, platinum and many others. The people on St Kilda lived off seabirds, which were culled from the islands' cliffs. After eating the birds, the remains were disposed off by plouging into the earth for the purpose of fertilisation. Once crops were harvested, the heavy metals would come back to the islanders. Heavy metals are toxic.
Dioxins are the products of combustion of carbon-based fuels in the presence of chlorine. They are very toxic at low concentrations. The islanders on St Kilda used peat for fuel. As the islands are only small, the soil is impregnated with salt, which (chemically) is sodium chloride. When the peats are burned, dioxins are formed. These are present in the smoke and the ashes. In the original blackhouse, there is no such thing as a chimney stack; smoke would dissipate through the thatch. After the peat had burned out, the ashes were scattered on the floor. Behold an environment rich in dioxins.
One of the more poignant aspects of life on St Kilda was its incredible infant mortality rate: 50%. Only 1 out of every 2 babies born would survive the first year of life. It was thought that the deaths were caused by infant tetanus (tetanus is commonly known as lockjaw). When a child was born on St Kilda, some fulmar oil would be applied to the umbilical stump after the umbilical cord was cut. Fulmar oil was kept in a dedicated bottle, but not at all in sterile conditions.
Recent research has suggested that the tetanus bacterium was not present in the oil at all, but in the soil.
The 8-day illness was thought to be the result of unhygienic living conditions, pollution by heavy metals and dioxins. It was eradicated after 1891 following the introduction of hygienic nursing practices.
Postscript: I do want to stress that many factors contributed to the decline and death of the community of St Kilda, but it would appear that health related problems were one of the main causes.