“A few breaths and it’s too late: you’re dead,” warns the Scottish Agricultural College (SAC) about the dangers of toxic slurry gas killing farmers and their cattle.
The new alert was caused by an incident two weeks ago reported by local SAC adviser Basil Lowman, when a beef producer in the Borders, who does not wish to be named, emptied some of the slurry stored under the slatted floors of his beef sheds.
After taking out two or three loads the farmer returned to find four large animals dead, suffocated by hydrogen sulphide gas.
The farm had just started using waste plaster board containing high levels of gypsum to help dry up the straw bedding being used in other buildings. Heavy rain had then washed some of that gypsum into the slatted shed and into the slurry store.
Gypsum, or calcium sulphate, contains high levels of sulphur, encourages bacteria to produce even greater amounts of hydrogen sulphide from the slurry. Hydrogen sulphide, which like hydrogen cyanide stops animals breathing, is so toxic the British army used the gas in chemical warfare attacks during the First World War.
“It is well known that mixing and handling slurry can produce this toxic gas, which is invisible, although it smells like rotten eggs,” SAC spokesman Ken Rundle said. “An important feature is that when you get a good whiff of the gas, it knocks out your sense of smell, so you may be unaware that you are continuing to inhale it, and also be unaware of its concentration.
“In a confined area it rapidly kills both cattle and humans by suffocation. It is also understood that adding silage effluent to slurry increases the risk as the nutrients in the effluent feed the bacteria in the slurry which are responsible for producing the hydrogen sulphide gas.
“SAC warns producers who are using waste plaster board or other gypsum sources to remember this and, as an additional safeguard, ensure that the product is stored and used in a way which completely avoids any potential contamination of slurry supplies. While this use of gypsum sources is relatively uncommon in Scotland it is believed to be more widely used in England where there is more available.”
SAC also said farmers should remember key safety points when emptying slurry stores:
z Before starting take all animals out of the building and open all ventilation, doors etc.
z Never enter the building when the pump mixing the slurry or emptying the store is working.
z Ensure there is always another person present who stays outside the shed and can summon help if needed, but without entering the building and endangering themselves.
z If entry is absolutely necessary, only appropriately supervised, competent persons, equipped with harness, lifeline and breathing apparatus, should enter slurry storage cellars and tanks.
NFU Scotland spokesman Bob Carruth said the union had reports of another nine dairy cattle dying on a Lanarkshire farm last week as a result of toxic gas generated by slurry mixing.
“As we head into spring, this is a very timely reminder from SAC of the dangers to man and beast from mixing slurry in an enclosed space,” he said.
“The dangers to farmers, their staff and their stock from mixing slurry are stark. SAC’s clear advice on removing stock from buildings, providing proper ventilation, staying clear of buildings while mixing is taking place and having staff support should be followed at all times.
“The loss of stock and the threat to human life are avoidable. Even though farmers may be under pressure to get slurry out, their own safety and the well-being of their staff and their animals must remain uppermost in their minds.”
The official who raised the issue, Mr Lowman, from Jedburgh, said: “I wanted to go national because if somebody had died, I would never have forgiven myself. It’s the human lives, not the cattle’s lives, that worry me.
“Suffocation can happen very quickly: two or three breaths and you know something is wrong, but after that it’s too late: you’re dead.
“Deaths have happened before in Northern Ireland: one farmer was overcome by the fumes in his shed, and another guy went in to save him, but neither came out.”
Symptoms of exposure to lower concentrations include eye irritation, a sore throat and cough, nausea, shortness of breath, and fluid in the lungs. Long-term, low-level exposure may result in fatigue, loss of appetite, headaches, irritability, poor memory and dizziness.