About fluoride and volcanic ash

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About fluoride and volcanic ash

Postby pfpcnews » Fri Apr 16, 2010 4:41 pm

SEE ALSO:
Severe dental fluorosis from volcanic eruption
http://poisonfluoride.com/phpbb2/viewtopic.php?t=612
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Gregory N - "Toxicity hazards arising from volcanic activity"
Surveillance 23(2)14-15 (1996) MAF Biosecurity Authority, Ministry of Agriculture and Forestry, New Zealand

Excerpts:

FLUOROSIS:

Fluorosis is one of the most important livestock hazards during the aftermath of a volcanic eruption. It is believed that it accounted for a high proportion of the 11,500 cattle, 28,000 horses and 190,000 sheep deaths in Iceland following the 1783 Lakagigar eruption.

The fluoride present in volcanic ash is water soluble and is readily leached out by water. So, if it rains or if the tephra settles on wet ground, fluorine soon finds its way into watercourses (within 2 hours). The fluorine is present as an adsorbed outer layer on the tephra particles. The adsorption occurs by condensation of fluoride onto the tephra particles in the plume above the volcano as it cools. The smaller tephra particles have a larger surface area, so carry more absorbed fluoride than the larger particles(5). The smaller particles are likely to be carried further from the volcanic source, and so their greater fluorine-carrying capacity extends the zone of potential fluorine poisoning considerably, even to regions where only a 1 mm thick deposit forms. It is advisable to sample and analyse the tephra or vegetation to identify hazardous regions.

Poisoning in sheep is likely to occur where the fluorine content of dried grass exceeds 250 ppm. In one incident in Iceland in which there were 7,500 deaths, levels reached 4,000 ppm. The most dangerous situations for grazing animals are usually some distance from the erupting volcano where the layer of fine grained fluorine-carrying tephra is so thin that it does not deter grazing. The fine grained tephra adheres to grass and so is more likely to be eaten.

Experience after the 1970 Hekla eruption shows that acute sickness occurred where the tephra layer was about 0.5 mm thick. At 1 mm thickness, 3% of the adult sheep and 8 to 9% of the lambs died. Acute poisoning occurred in the first days after the tephra fall and was accompanied by convulsive seizures, pulmonary oedema and kidney and liver damage. Experimental trials involving NaF intoxication showed that the principal signs of acute fluorosis were depression, salivation, hyperpnoea, nasal secretions, inappetance, blindness, ataxia, coma and death(6). The rumen, reticulum and abomasum showed epithelial necrosis and hyperaemia, oedema and haemorrhage in the lamina propria and submucosa. The kidneys showed necrosis of epithelial cells in the proximal convoluted tubules.

Chronic fluorosis occurred at Hekla where the layer of ash was 1 mm or more thick. Serious outbreaks of volcanic fluorosis have also been reported for sheep and cattle in Chile(7). The ash contaminated 4,000 sq km of grassland, and cattle started showing clinical signs of osteofluorosis after about 4 months. The main clinical signs were weight loss and lameness. Diarrhoea, tinged with the colour of the ash, occurred in many of the sick animals. In some stock there was kyphosis, and exostoses were accompanied by intense pain when the long bones were palpated (especially the metacarpus). There was a high degree of attrition of the incisors with almost total crown loss. The fluoride content of serum and bone were elevated as was serum alkaline phosphatase activity.

In sheep, lesions are found more commonly on the jaws than on the legs. Those on the legs occur in more advanced cases. There are also lesions in the nose and mouth, and the hair around the mouth may fall out, possibly because they are ‘bottom’ or ‘hard’ grazers and are exposing their muzzles to the ash. Similarly, sheep and deer are more prone than cattle to teeth attrition, probably because they take in more ash. Another tooth condition is ‘spiking’, where outgrowths develop on the molars and can make chewing difficult. In Iceland a special type of pliers was used at one time for breaking off these outgrowths in sheep and horses. The teeth may also develop the `ash teeth' condition, with yellow or black spots that may extend over the entire surface before a tooth falls out.

Soluble fluoride is readily absorbed by the gut by a passive rather than active transport process. Attempts to reduce fluorosis with various calcium, magnesium and aluminium salt drenches have met with only partial success. No effective prophylactic treatment is available.
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New Zealand MAF Biosecurity Authority, Ministry of Agriculture and Forestry "Impact of a Volcanic Eruption on Agriculture and Forestry in New Zealand" (2001)
http://www.maf.govt.nz/mafnet/rural-nz/ ... /httoc.htm
Section 4.3 Distal hazards
Pyroclastic Fall Deposits - (Ash)
4.3.1 Impact On Livestock

Excerpts:

Ashfalls may be poisonous to stock resulting in clinical diseases which include hypocalcaemia, fluorosis, forestomach and intestinal damage and secondary metabolic disorders.

Fluorine aerosols attached to fine tephra pose a significant threat to livestock (Gregory & Neil 1996). Poisoning occurs where the fluorine content of dry grass exceeds 250 ppm. Before death, the poisoning causes lesions in the nose and mouth and hair to fall out around the mouth. Fluorine poisoning of livestock has occurred a number of times in Iceland (Thorarinsson 1979). The eruption of Lakuggar in 1783 killed 50% of the island's horses and cattle and 79% of the sheep. In the 1947 eruption of Hekla, only sheep were effected with other animals (cattle, horses, cats, dogs and poultry) unaffected. In 1970 fluorine poisoning occurred in areas of Iceland which received only 1 mm of ash."

As a result of 5 mm ash fall on the Rangitaiki Plain (Taupo) during the 1995 Ruapehu eruption, approximately 2000 ewes and lambs (2.5% of the area's sheep population) were killed as a result of eating ash-affected pastures. Autopsies of the dead animals suggest fluorine poisoning or pregnancy toxaemia was the cause of death (Gregory & Neall 1996). Three Ayrshire dairy cows died at Atiamuri in June 1996 (pers.comm. MAF). It was reported that they stopped eating, showed signs of lethargy before dying after swallowing quantities of ash. Toxic levels of fluorine were found in the dead animals blood. The Department of Conservation also reported the death of a number of wild deer in Kaimanawa Ranges, downwind from Ruapehu, following the two largest October 1995 eruptions (possibly up to 5% of the sika deer population).

Volcanic eruptions inject water vapour (H2O), carbon dioxide (CO2), sulphur dioxide (SO2), hydrochloric acid (HCl), hydrofluoric acid (HF) and ash into the atmosphere. HCl and HF will dissolve in water and fall as acid rain whereas most SO2 is slowly converted to sulphuric acid (H2SO4) aerosols.

Where there is acid rain following an eruption, pastures will be scorched and die (Gregory et al 1996).
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