From the air, England looks as if it is preparing for an emergency. Where once farmers grew wheat and barley, a tide of oilseed rape, bolstered by EU subsidies, has swept across the country. Slicks of Day-Glo yellow lie daubed across the land, cladding the countryside in a protective suit, as if it were caught in an intercontinental crisis. Some people think that is exactly what it is.
There are those who admire the luminous brilliance of the crop, and there are those who complain it has created a garish patchwork which has despoiled the glory of the English countryside. But concern about the spread of oilseed rape is not only aesthetic. This year, with record temperatures and low rainfall in April, it flowered early, releasing its sweet, cloying scent along with sackfuls of pollen. And pollen, to Britain's 13 million hay fever sufferers, spells trouble.
As the flowering season has peaked in what threatens to be a record year for hayfever, so have complaints from people living and working in, or merely passing through, the areas where oilseed rape is grown. Stricken by rasping throats and itchy eyes, some claim the yellow tide is destroying our health as well as our countryside. Others insist it is unfairly blamed.
Two letters, published in The Daily Telegraph last week, encapsulate the dispute. Anna Dickie of Sudbury, Suffolk, described bitterly how the county was "blighted by smelly fields of rape which brings misery to hayfever sufferers and asthmatics". Even the family pets suffered, she added. "We can't hang washing out to dry as clothes become impregnated with rape pollen. My asthmatic cat is particularly affected by this horrid crop and has to be treated with daily inhalers and pills at this time of year."
A couple of days later Chris Clarke from Moelfre, Abergele in north Wales, sprang to the crop's defence. "We consider ourselves blessed by large areas of rape. Our bees are busy now converting its nectar into honey in one of the best and earliest starts to the beekeeping season in memory.
"My wife who suffers seriously from hayfever, wanders among our hives at the rape fields without ill effects. Closer to home she suffers and we think it likely that birch, lilac and other pollen is the cause."
Who is right? Allergy specialists favour Mr Clarke's analysis. In the league table of hayfever triggers, oilseed rape ranks low. True allergy to rapeseed pollen is rare, specialists say. On the other hand they do not dismiss Ms Dickie's view. Even though true allergy to rapeseed pollen may be rare, it can still cause widespread irritation to large numbers of people thanks to the organic compounds it gives off and its garish colour and overwhelming smell. Whether this reaction is correctly labelled "hayfever" or not is immaterial to those who suffer its symptoms.
This year the hayfever season has started earlier and threatens to last longer than ever. Boots, the high street chemists, released figures last week showing sales of hayfever remedies were up 146 per cent compared with the same time last year. In inner cities, where pollution is worst, sales are up even higher at 177 per cent above last year.
Conditions have been ideal for pollen production with plenty of rain in January and February followed by a long hot spring promoting good grass growth. People have been out and about in the hot weather at weekends, exposed to tree pollen, and there is already some grass pollen, the main hayfever trigger, about.
Professor Jean Emberlin, director of the National Pollen and Aerobiology Research Unit at the University of Worcester, said: "We could be facing a record year for hayfever. In 2006 we had enough rain to keep the season going and we saw record amounts of pollen across the Midlands. This year it will depend on how much rainfall we get.
"We had enough rain in the spring to get good grass growth so we are expecting the main grass pollen season to start in the last week of May, a week or 10 days earlier than average."
Hayfever is critically dependent on the weather. As temperatures rise, pollen seasons are lengthening and the pollen itself is provoking a more powerful reaction, especially in cities where pollution increases the irritant effect.
This year, the Meteorological Office says there is a 70 per cent chance of unusually hot weather and a one in eight chance of a heatwave. Global warming was identified as a factor behind rising pollen counts by the UN's Intergovernmental Report on Climate Change in 2001. Last year had one of the warmest summers on record and one of the worst for hayfever.
Professor Emberlin said: "Temperature stress, pollution input and climate change all add up to more pollen, a longer pollen season and pollen that is more allergenic."
The message is that if you think it is bad now, it is bound to get worse over the next few weeks. Most people currently suffering symptoms are reacting to tree pollen, made worse, in towns and cities, by car exhausts. Air pollution from exhaust fumes seems to have an enhancing effect on the release of allergenic substances, particularly from birch pollen. Pollen in cities thus causes more allergy than pollen in the country.
By the end of the month we will be in the peak grass pollen season, which affects many more people, and is the commonest cause of hayfever. Even though this is still a week or two away, there is already a fair amount around, because of the warm conditions.
But when people cough and itch, like Ms Dickie's cat, they look around for the cause and the strong smelling, canary yellow fields of oilseed rape are the most obvious culprit.
An estimated 600,000 hectares of land are covered in the bobbing yellow flower heads, which were practically unknown in Britain 30 years ago. Production last year grew by 17 per cent and is predicted to top two million tonnes next year by the Department for Rural Affairs.
For farmers it turns a healthy profit with unlimited demand for the seed as a biofuel - much of the UK's production goes to Germany to make biodiesel - and to make "extra virgin rapeseed oil", an alternative to olive oil.
Its unhealthy effects on the populace remain a matter of dispute. Until the 1980s, when the acreage under cultivation rapidly increased, there was no public suspicion that it might be harming health. Nor was the anxiety in Britain seen in other countries.
As the crop advanced across the country during the 1980s and 1990s, concern mounted and in 1996 the UK Medical Research Council decided it was time for a closer look. Its Institute of Environment and Health in Southampton launched an investigation which concluded there was "no clear evidence" that oilseed rape has adverse effects on health. Allergy to rape pollen was rare, even in areas of intense cultivation, and those affected tended to be multiply sensitive to other substances with no indication that rapeseed was the trigger.
Rapeseed pollen is sticky and heavy and transmitted by insects (unlike grass pollen which is disseminated on the wind). So it does not travel far and only those within 50 metres or so of a field are likely to be in range. Some experts have suggested that mould which affects the crop during seed ripening could trigger a reaction but the researchers found no evidence for this.
However, oilseed rape does give off volatile organic compounds such as terpenes and aldehydes which could account for its irritant effect on the mucous membranes of the eyes, mouth and throat. Yet the Southampton researchers remained puzzled as to why in other rapeseed-growing countries such as France, Germany and Denmark, there was no public concern.
Specialists today say that in the 10 years since publication of the MRC report, no significant new evidence has come to light to alter its conclusions.
Professor Pamela Ewan, consultant allergist at Addenbrookes Hospital, said: "The amount of allergy to rapeseed is very low. People think they are allergic to it because of its bright colour and powerful smell when they are really allergic to other pollens that they can't see. There could be some adverse reaction to the volatile chemicals the plant produces. But I think the perception is much greater than the reality. Grass pollen is by far the most potent cause of hayfever in Britain, though it is different in other countries. In the US the main cause is ragweed."
Others take a less rigorous approach to the science, preferring to emphasise sufferers' reported experience. Muriel Simmons, spokeswoman for the charity Allergy UK, said: "Rapeseed very rarely triggers an allergic response, but it may be an irritant. For sufferers from rhinitis or asthma it may exacerbate their symptoms through the fumes it gives off. The best way to deal with this is to close the windows of the car if you are driving through an area of oilseed rape. If you are affected, the symptoms disappear in 10 minutes once you are through the area."
She added: "I think it is worrying that we are seeing the yellow tide advancing and the number of fields turned over to rapeseed spreading. Whether it is affecting the immune system or not is irrelevant - it is making a lot of people feel very uncomfortable."Reuse content