August 14, 2024

expert reaction to reported spill of sodium cyanide in Walsall canal

Scientists comment on a spill of sodium cyanide in a Walsall canal.

Dr Andrew Shaw, Assistant Professor of Toxicology at Heriot-Watt University, said:

“Sodium cyanide is an extremely toxic substance, as it rapidly inhibits fundamental life functions.

“However, the risk is poses in this case is dependent on how much was released and the amount of water—and flow rate of that water—it was released in to.“Ecotoxicologists will have to work to assess this situation and predict its severity.”

Prof Alastair Hay, Professor Emeritus of Environmental Toxicology at the University of Leeds, said:

“Sodium cyanide breaks down in contact with water producing hydrogen cyanide, a toxic gas that smells of almonds.

“Sodium cyanide can be absorbed from the gut,  is a inhalation hazard and may be a problem through skin contact.

“There are occupational exposure limits of 5 mg per cubic metre; this can be treated as a relatively safe level for healthy men and a sort of benchmark.

“The chemical is often used in various chemic manufacturing processes,  electroplating,  and for separating gold and silver from ore.

“Cyanide is a cell poison which affects all living systems. It inhibits the enzyme cytochrome C oxidase in the electron transport chain in cells.

“The approach to clean up will of course be to first contain and prevent further release. Once in water the sodium cyanide will break down in part to hydrogen cyanide , which being lighter than air will rise into the air and disperse. As long as people are kept away from the area affected there should be no risk as hydrogen cyanide ( the principal concern) will disperse. This is why the authorities will have cordons in place.

“Those monitoring will be assessing cyanide levels in water and possibly hydrogen cyanide in air.

“Clearly the more the chemical is diluted the lower the risk. But there will be a considerable impact on local fauna.  I doubt they will decide to drain a section of the canal but this will depend on how much has been released.

“Decisions about risk will be governed by the levels of cyanide detected. All dead creatures will have to be removed and incinerated or buried to ensure nothing else is poisoned.”

Dr Jonathan Paul, Senior Lecturer in Geosciences at Royal Holloway, University of London, said:

“Spillages such as this are cause for concern and something that could take days to remedy.

“Sodium cyanide is very commonly used in mining to leach gold and silver, but it’s also used in the production of paper and plastics, and less commonly in the processes of fumigation and electroplating, so there are plenty of places the spillage could have come from.

“Uncontrolled spills into waterways present a major ecosystem hazard, especially when the water might be used for public supply (e.g. aquifers). It’s also a risk to the public water supply if the canal water meets leaky sanitation lines. Then the greatest risk for people would be encountering the toxic canal water, for instance via touch.

“Ingestion of water containing a sufficiently high concentration of sodium cyanide can result in classic poisoning symptoms, i.e. nausea, weakness, aches, and potentially a loss of consciousness – but that is entirely dependent on how much is ingested and the concentration of the chemical.

“Numerical and analytical modelling is being carried out as quickly as possible, in order to estimate the speed and direction in which the cyanide plume might spread. These predictions will be benchmarked against measurements of toxicity, dissolved oxygen levels, and cyanide concentrations.

“The cheapest remediation technique is simply to dilute the contaminated water until cyanide levels drop to safe limits, such as bringing in fire engines to pump copious amounts of water into the river; however, filtering and other energy-intensive techniques like reverse osmosis might be locally applied in the case of severe spills.

“When it comes to the ecosystem, poisoning of higher-order aquatic life will be affected, such as the fish rather than plants.

“Unlike some pesticides, cyanide doesn’t accumulate up the food chain so won’t affect the entire aquatic ecosystem, as it breaks down much more quickly.”

Declared interests

Alastair Hay: I have no conflicts of interest.

For all other experts, no reply to our request for DOIs was received.