Deadly Secrets of Diss Mere
Diss Mere has been seriously contaminated for 1,000 years; and it could be caused by traditional industries.
This is the conclusion of Dr. Handong Yang of the University of London, who has compared the case with that of Minamata Bay in Japan and the Amazon, which led to many deaths.
The culprit is mercury, reaching a peak of contamination in the 19th century.
A previous study had shown that sediments from the mid 1800s taken from Diss Mere were contaminated to an extraordinary level – significantly higher than in modern lake sediments across London..
Although local hemp cultivation and the traditional weaving industry were abandoned a hundred years ago, this contamination still exists in the catchment and affects the lake.
The main industry in the Diss area was wool and linen from the 1100s onwards; and hemp growing from the 15th to the 17th centuries.
Pesticides may have been used to prevent insect damage in the weaving industry. The mercury contamination may reflect an increase in the scale of processing from household to a more industrial level.
The manufacture of hemp cloth became the principal industry in the 18th century and lasted until the mid-19th century, increasing mercury contamination in the sediments even further.
The local weaving industry was large, with three Diss factories employing over 200 people before 1800.
In 1773 Norfolk produced an eighth of the total fibre in England mainly by growing hemp, with Diss as one of the outstanding producers.
In the early 19th century, the weaving industry and wool trade declined in the region.
The period of maximum contamination around the 1850s may derive from the dumping of stored materials such as pesticides, fibre treating reagents and dyeing materials due to this decline.
“Local people have been exposed to a heavily contaminated environment and their health may have been affected during the period of peak contamination,” says the report.
The catchment soils still contain a high level of mercury and this has affected the lake environment.
Future research is needed to determine the extent and scale of the contamination in the area and within the lake ecosystem, particularly concentrations in fish and aquatic plants.
Dr. Yang’s article, Historical mercury contamination in sediments and catchment soils of Diss Mere, can be read in the museum. We helped him in his research.
Basil Abbott (Diss Museum)