The Food Standards Agency (FSA) has reassured the Environment Agency that they found no cause for concern in test results from fish samples taken recently from the River Derwent following the silt incident at Glebe Mines in January 2007. This is the second batch of fish samples to be checked and cleared by the FSA since the incident.
Having assessed the results of tests on fish samples for the presence of heavy metals, the FSA concluded that the food safety risk from consuming grayling and trout from this site would be minimal. None of the results gave cause for concern.
They found that the levels of lead, copper, zinc, and arsenic in the Derwent fish samples were not significantly different from levels normally observed in fish. Concentrations of lead, mercury and cadmium were below permitted limits. They assessed that consuming three 140g portions of the fish in a week would contribute to only 8% of the safety guideline for cadmium.
Mark Cunningham, the Team Leader who led the investigation said, "There has been some speculation about the safety of the fish and I hope the outcome of the FSA’s assessment will help to put minds at rest. We will continue to monitor the river for as long as it takes."
Jillian Spindura from the Food Standards Agency said: “The results of our tests showed there is no cause for concern for consumers. As a precaution we have also recommended that fish are tested later to monitor the levels of metals in fish caught here.”
The silt that escaped from the Glebe Mines lagoon was formed from naturally occurring rock which, due to the local rock formation, contained background levels of some metals, such as lead. As part of our monitoring programme, we have taken chemical, biological and plant samples, as well as fish tissue samples, to determine whether there was any impact on the food chain. The FSA results confirm that there has been no impact .
Immediately after the incident the Environment Agency began a detailed investigation. This was split into three phases:-
- The formal investigation, looking into the cause of the incident, which has now been completed. The case file has been sent to our legal team for a decision on whether further action should be taken.
- The recovery phase, concerned with the removal of the silt. We have assessed the best method of removing the silt without causing harm to the environment and work is underway.
- The monitoring phase, looking at the short and longer term impacts, which is ongoing.
Our monitoring programme began immediately after the incident. As well as any possible impact on the food chain, we were concerned about the physical effects of the silt on the stream bed. The incident left a blanket of sludge which covered the stream bed and deposits could be seen in the river at Calver. This blanketing had an immediate effect on the invertebrates (the small water creatures that fish feed on) but our tests have shown that they recovered rapidly.
We were also concerned that the silt could have settled into the river gravels, damaging the habitat for invertebrates and making the gravels unsuitable for fish to spawn in. We took samples of the bed of the stream for analysis. The initial tests did show some local impact, so we have recently repeated the work. This will help in determining how successful the clean up will be.
We will continue to monitor the river for the foreseeable future and modify our programme in light of our understanding of the effects of the pollution. However, to date we have not found anything which causes us concern.