Foot-and-mouth pyres in the UK are releasing more potentially cancer-inducing chemicals than all its hazardous factories, but scientists say public health risks are low.
Official UK figures indicate that in six weeks of the crisis, up to April 6th, the pyres had released 63 grams of dioxins. This compares with 88 grams released by all of the UK's biggest, most dangerous factories in a year.
Dioxins are carcinogens and may cause other health effects, such as reduced fertility, impaired development in infants, and possible organ damage, according to the US Environmental Protection Agency.
While some dioxins are formed naturally, most are the by-products of human activity.
They can be released in air or water and can eventually enter the food chain.
Scientists say the foot-and-mouth pyres in the UK would not burn at a sufficiently high temperature to eliminate dioxins. However, the health risk from the dioxins emitted from pyres is "abysmally low", said Prof Emer Colleran, of NUI Galway's department of microbiology.
Prof Howard Sidebottom, of UCD's department of chemistry, said the areas in the UK where there was a high concentration of pyres - Devon and Cumbria - had a low population density. Current weather conditions would also disperse the dioxins.
As regards the possible health risks, Prof Sidebottom said a similar situation has occurred before, during the UK's last foot-and-mouth epidemic in 1967. The outbreaks were then concentrated on a region around the Welsh border, where some 433,987 animals were culled.
Prof Sidebottom said there did not seem to be any evidence of harmful effects on people in the area.
A spokesman for the British Ministry of Agriculture said it is working within current Ministry of Health guidelines for the disposal of the carcasses. He emphasised there were no disposal options which were without risk.
The Ministry of Agriculture also quoted a report which said the dioxin emissions from the pyres were equivalent to the emissions from two bonfire nights.
But Mr Adrian Bebb, food campaigner with Friends of the Earth, described this comment as a "pathetic spin".
He said the dioxin risk was "very, very worrying. These are big burnings in concentrated areas, which are very different to lots of small bonfires. The practice of burning and burial should be stopped immediately".
Farmers could be doubly hit by foot-and-mouth. Not only would they would see their stock being culled, but they might not be able to sell products in future because their land had been contaminated.
Friends of the Earth believes the preferred options outlined by the Environmental Protection Agency - the use of rendering plants, controlled incinerators and landfills - should be fully used before burning or burying on farms.
The EPA's guidance on emergency disposal of animals recommends rendering as the preferred method of disposal for animals culled to try and limit the spread of the disease.
Prof Colleran said she was concerned the uplift of hot air from the pyres themselves may spread the virus.
Prof Jim Bridges, professor of toxicology at Surrey University, said: "I am always concerned when we have uncontrolled burning of any kind that we probably don't know enough about what is happening in that process."
Dioxins form at high temperatures in the presence of carbon, hydrogen and chlorine. Pyres contain chlorine because they are built with creosote-soaked railway sleepers and tyres. The dead livestock contain hydrogen and carbon compounds, and the fires are lit with hydrocarbon fuels such as kerosene.