Did climate change help fuel disease during the Industrial Revolution?

A study of human remains from a cemetery in North Shields, England, has suggested that changes in the amount of sunlight may have contributed to the health problems faced by children of that time.

These findings suggest that climate may have contributed to childhood health problems during an age already characterized by industrial pollution and densely populated conditions. They do not conclude that climate change caused the prevalence of rickets.

However, the researchers do suggest that reduced sunlight may have acted as a multiplier of other risks, leading to vitamin D deficiency and rickets, a disease of the growing bones.

Climate and industrialization may have created a double health burden

The Industrial Revolution brought pollution, overcrowded housing, poverty, and hard work. It occurred during the latter part of the Little Ice Age, an extended period of climatic cooling associated with several factors, including volcanic activity and prolonged periods of low solar activity.

Ultraviolet B (UVB) radiation in sunlight triggers vitamin D production in the skin. Children who are deficient in vitamin D can go on to develop rickets, a condition which leads to weak and deformed bones. Diet has an effect on vitamin D levels as well.

Durham University researchers are suggesting that the reduced UVB exposure may have been a contributing factor to the health problems associated with industrialization. This does not mean the scientists are saying that the cold itself was the cause of rickets, nor are they claiming that the volcanic eruptions were the sole explanation for the disease.

What they're proposing is that the atmospheric changes may have reduced the amount of sunlight available to people who were already in a vulnerable position.

Teeth and burial records reveal clues about childhood health

Researchers examined 30 teeth from 21 individuals buried at Coach Lane Quaker cemetery in North Shields, which was in use between 1711 and 1829. Disruptions in the growth of the dentin can preserve a record of the stresses that a child could have experienced.

Historical burial records offered another piece of evidence. They enabled the researchers to work out the birth years of 109 members of the community. Ninety-one of these individuals had been born during or within 10 years after a major volcanic eruption. Forty-one were born during periods when volcanic activity coincided with unusually low solar activity.

Together, the evidence allowed the researchers to look at whether the periods associated with potentially reduced sunlight coincided with signs of disrupted mineral development in the population. However, the lack of individual identification means they cannot establish whether a particular individual experienced those environmental conditions or prove that a particular eruption led to a dental defect.

The findings suggest a contributing factor, not a single explanation

Volcanoes emit sulphur dioxide into the atmosphere, which in turn can form sulphate aerosols that deflect sunlight and temporarily reduce the amount of solar radiation that reaches the Earth's surface. Low solar activity is a different proposition altogether and involves changes in the Sun's output. This study looks at both of these as potential influences on the amount of sunlight available in the past.

The Maunder Minimum (1645-1715) and the Dalton Minimum (1790-1830) were periods of very low solar activity. The latter of these coincides with the last few decades of the cemetery's use. Additionally, the dental samples were small, and the cemetery lacked grave markers and detailed burial plans, making it impossible to match most recovered remains with individuals listed in the historical register.

The research points to an environmental factor rather than giving a complete explanation for the poor health of the time period. Pollution, diet, housing, and poverty may also have contributed to vitamin D deficiency.

The study examines historical natural climate variation rather than modern-day human-induced global warming. Changing sunlight may have contributed to vitamin D deficiency, but the findings do not establish how much of the resulting disease can be the result of climate conditions alone.

Sources: ScienceDirect , Frontiers , PLOS , Journal of Space Weather and Space Climate

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