Arsenic Health Risk at UK World Heritage Site

Would you encourage your children onto a playground you know is heavily contaminated with arsenic?

Most probably not!

But the public is encouraged to use the heavily arsenic contaminated grounds of Devon Great Consols mine near Plymouth (UK) for recreation: walking, riding, biking, picnicking, exploring…

You think that’s crazy? You may be in a minority!

In 2007, the Tamar Valley AONB were successful in attracting £7 million investment from the Heritage Lottery Fund, Europe, County Councils and others for the Mining Heritage Project. Works commenced with consultancy surveys and finished with the opening of 25 km of trails that allow the public to access some of the most contaminated land in the country.

Some of this money was spent on remediation and mitigation: shafts were fenced off and signs were installed (not barriers) that intended to prevent access into some of the most polluted parts of the site.

Today, a lovely video praises this site for its family-friendly atmosphere and shows people jogging and biking on highly polluted ground – oblivious of the dangers they are in.

What’s more: the land owner permits a mountain bike club to use one of the most contaminated mining waste heaps for downhill practice and competitions.

Time to get real:

Arsenic is a deadly poison: the dose necessary to kill a person is somewhere between 100 mg and 300 mg, or one tenth to roughly one third of one gram of inorganic arsenic.

Chronic poisoning, the type people around the world are exposed to as a result of contaminated water supplies and occupational exposure, leads to serious consequences, including cancers of many organs, skin diseases, abdominal pain and diarrhoea, confusion and memory loss, neonatal morbidity and mortality, lung diseases and disruption of endocrine and haematological systems (Ratnaike, 2003).

Is anybody doing something about this?

I’ve tried for over a decade for this contamination to be taken seriously with respect to environmental health. Now, we’ve published work relating to human health.

Here is what we found:

  • across the site, the enrichment with arsenic is 600 fold relative to the soil concentrations in the Tamar river catchment (based on median)
  • concentrations ranged from around 140 to 75000 microgram per gram (µg/g) of soil or dust (that’s 7.5% by weight)
  • health-based soil guidelines values developed by the Environment Agency of England and Wales are 179 µg/g for park-type soil and 640 µg/g for commercial land
  • ingestion simulation with gastro-intestinal fluids testing the biologically accessible concentration in soils showed that most samples exceeded the park-type soil level
  • of 98 measurements taken on publicly accessible trails and places on site, only one (1) showed arsenic concentrations suitable for parkland and only 13 were suitable for commercial activities
  • particles in all air samples taken along trails and mountain bike tracks exceeded the current European Directive annual average target value of 6 nanogram arsenic per meter cubed (ng/m3), in one case by more than 10 times
  • lung fluid simulation showed that target values for arsenic were exceeded in many samples, indicating that the biologically accessible concentrations were too high
  • the calculated Index Dose of Minimal Risk from ingestion and inhalation of arsenic is 0.302 microgram per kilogram of body weight per day (µg/kg bw /day) and it is estimated that children ingest around 100 mg soil
  • a child of 1-2 years old and weighing 9.8 kg visiting the sites for 6 hours may ingest 25 mg of soil containing on average 13000 µg/g arsenic would be exposed to more than 10 times (33 µg/kg bw /day) the Index Dose of Minimal Risk
  • the equivalent exposure is more than 7 times (2.3 µg/kg bw /day) the Index Dose of Minimal Risk

What does this mean?

  • arsenic concentrations at Devon Great Consols are sufficiently high to be a public health concern
  • frequent visits, or indeed working on site, could significantly increase one’s risk of chronic arsenic poisoning
  • activities that encourage airborne dust, such as mountain biking, riding and walking in dry conditions increase the risk of inhalation
  • deviating from permissive paths onto mine waste material that is not fenced off increases the risk to health
  • mitigation measures are urgently needed to protect the public and employees

What can be done?

In my own opinion, and not necessarily reflecting the opinions of my co-authors of the scientific paper, the site should be instantly closed the general public. However, more pragmatically, and as a minimum, leisure pursuits should be minimised to less contaminated trails, areas fenced off that are highly contaminated and comprehensive information signage installed. Furthermore, the contaminated car parking area and timber storage yard to the north of the site must be closed to protect workers and visitors. The public must be excluded from the area of highly contaminated remains of arsenic processing and refining installation (calciners and labyrinth). Mountain biking activities must be disallowed on mining waste.

More mid-term, and in the interest of re-opening the site, contaminated trails could be remediated by removing surface layers and replacing them with inert materials.

In addition, covering the mine waste to prevent water ingress, erosion and dispersal of contaminated material would be a long-term target to protect the site and surrounding farmland and dwellings. Large-scale engineering solutions are expensive, disruptive and not sympathetic to the mining heritage. Therefore, I would suggest a phyto-stabilisation approach through re-vegetation.

I can only hope that someone out there cares enough to make it happen!

If you want a little bit more of the back story – go to my post ‘Challenging Habitat‘ and follow the links in the introductory paragraph.

References

All detail stated here has been either linked to external sources or is referenced in the published scientific article:

Braungardt C, Chen X, Chester-Sterne D, Quinn JGA, Turner A (2020). Arsenic concentrations, distributions and bioaccessibilities at a UNESCO World Heritage Site (Devon Great Consols, Cornwall and West Devon Mining Landscape). Environmental Pollution 264.

This work is accessible free of charge until 5th July 2020 from the publisher at: https://authors.elsevier.com/a/1b18AzLNSVgDK

After that date, please contact me directly for an electronic copy at cbraungardt@plymouth.ac.uk

Image

View over Anna Maria waste heap from one of the trails at Devon Great Consols mine. Photo: C Braungardt, 2018.

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