A COUPLE of years ago it would have been as fantastical as some of David Icke's prophecies to suggest a connection between those tasteless out-of-season strawberries and the Antarctic ozone hole.
That connection is now becoming a global issue: methyl bromide, a highly toxic gas used for a vast range of purposes, including the sterilisation of soil in greenhouses, appears to be outstandingly effective at destroying the Earth's ozone layer.
Methyl bromide is likely to be the most intractable issue at the meeting of Montreal Protocol nations in Copenhagen next week.
The United States leads in wanting to phase out methyl bromide by the year 2000 - propelled partly by vice-president elect, Al Gore ("Mr Ozone"). The EC has just agreed a freeze at 1991 levels by 1995. Britain is prepared to go further, with a 25 per cent cut by 2000 if other countries do likewise. Environmentalists want a phase-out by 1995.
Doug Parr of Friends of the Earth said: "This could be one of the most powerful chemicals involved in ozone depletion, and we have to phase it out as soon as possible. We shall be pressing for an application of the precautionary principle."
According to the latest scientific assessment for the United National Environment Programme (UNEP), chaired by American Dr. Bob Watson, bromine derived from methyl bromide is 30 to 60 times more efficient than chlorine at destroying ozone. Model calculations indicate that man'semissions of methyl bromide may have accounted for up to 10 per cent of the current global loss of stratospheric ozone, the thin layer of molecules that shelters the Earth from the Sun's harmful rays.
Since 1973, when Dr Sherry Rowlands discovered the ozone depletion potential of CFC's
(the chlorofluorocarbons widely used in spraycans), the battle has raged over chlorine-based compounds. Although bromine comes from the same chemical family, it was thought to languish low on the list of nasties, since only a quarter of the Earth's emissions of methyl bromide come from man-made sources - algae in the sea have been making the stuff for millennia.
A recent re-evaluation of bromine has shown that its high ozone-depletion potential in polar and middle latitudes has been overlooked. Bromine also appears to act faster when chlorine is present. Since the UNEP report in June, the world has been faced with a problem potentially even more difficult than it faces in phasing out CFC's, halons, methyl chloroform and carbon tetrachloride: how to stop using a chemical on which the world's food trade depends, and the use of which, in many countries, is specified by law as a quarantine measure.
Methyl bromide is described by users as a unique chemical, able to kill everything from nematodes in soil to fungus in vines and from rats in airliner cargo holds to weevils in wheat. It has been in widespread use for at least 30 years. Since it is highly toxic in the short term, extensive safety precautions are essential. The user must wear a respirator.
Of the 66,000 tonnes of methyl bromide used worldwide each year, 80 per cent go to sterilise soil so that crops may be grown continuously under glass. The other 20 per cent find a wide range of applications: quarantine purposes, fumigating ships and containers, flour mills, art collections and stored commodities such as rice, coffee, tea, nuts, coconuts, spices, dried fruit, fish-meal and potatoes.Many developing countries are dependent on the fumigation of products before export: $16 billion-worth of goods exported to Japan have to be fumigated with methyl bromide. The United States insists that the Chilean grape harvest is fumigated before reaching its shores. Australia insists on fumigation of timber products to prevent the importation of wood-boring wasps.
Methyl bromide has given pause for thought in agricultural circles, where the assessment of pesticides has often, notoriously, overlooked important environmental effects. The Ministry of Agriculture's Advisory Committee on Pesticides gave methyl bromide a clean bill of health as recently as April, but this applied only to its residues on food.A ministry spokesman defended this oversight: "Whether methyl bromide is safe for use as a pesticide is distinct from whether it is environmentally safe." A glib distinction.
With so many people relying on methyl bromide for food, can application be limited? Industrial users at UNEP's Washington meeting in June estimated that between 30 and 90 per cent of its use in soil sterilisation could be substituted by 2000.
Emissions from fumigation chambers could be recycled or destroyed.
In the Netherlands, methyl bromide is already banned for soil sterilisation after a scare 12 years ago in which it was found to contaminate ground water. Now the Dutch glasshouse industry uses a mixture of steam sterilisation of soil and hydroponic methods of cultivation.
In Britain, the big users are more positive than were the chlorine manufacturers a decade ago. The British Pest Control Association has said that it will phase out methyl bromide as soon as possible if it is shown to destroy ozone - there are many scientific uncertainties to clear up in a new 18-month study by UNEP.
Colin Smith of Rentokil, who is a spokesman for the association and a member of the Government's Montreal Protocol Advisory Group, points out that methyl bromide is the only known rapid treatment for a wide range of infestations in perishable foodstuffs or of rats in aircraft. Other fumigants, such as phosphine, are available, but in low temperatures take 10 days to be effective.
"The whole of Western civilisation is geared to the fast movement of food through the chain," Smith said. "Stop fumigation overnight and world trade could grind to a halt." He claimed that in Africa the effects of not fumigating food could be tragic.
The manufacturers are resisting a ban altogether. David Box, whose company Bromine and Chemicals makes its bromide from the Dead Sea, said: "There is no single alternative to methyl bromide in its wide applications"
Clearly many industries will need time to adapt, but time is precious if we are to prevent significant ozone depletion in the Northern hemisphere. Joe Farman, the British scientist who discovered the ozone hole, reflects: "Why can't we go back to eating what we grow ourselves, rather than carryingit half way round the world and eating it out of season when it is utterly tasteless?"
