Pollen Predictors

Allergic disease is a major public health problem with an annual economic burden of up to €151 billion in the EU alone.

Pollen allergy has increased rapidly in recent decades but climate change could see hay fever misery set to increase for millions more across the globe.

Hay fever or Allergic rhinitis is a common allergic condition that is estimated to already affect 40 per cent of Europeans at some point in their life.

Whilst climate change has clear implications for human health - with warmer climates and higher sea levels potentially increasing infectious disease and causing freshwater or crop shortages - until recently it was unknown what the effect of climate change on production of allergens and therefore allergic disease might be.

Scientists at UEA, in collaboration with several European institutes, are now able to predict how climate change could see incidences of pollen related allergic disease rise.

Prolonged exposure

Originally called ‘hay fever’ from the incorrect assumption that symptoms were brought on by the smell of new hay, Allergic rhinitis is now one of the most common allergies in the world affecting up to 1 in 5 people.

It is caused by an allergy to pollen – including tree pollen (released during spring), grass pollen (released during the end of spring and beginning of summer) or weed pollen (especially released during late summer and early autumn).

When the body is exposed to allergens (such as pollen, dust mites or animal dander) it can become sensitive to it, believing itself to be under attack and producing antibodies to flush the substances out – hence the classic symptoms of sneezing, watery eyes and runny nose. This causes irritation and inflammation of the nose, eyes and throat and can also aggravate asthma.

Occurrences of hay fever are already increasing in many parts of the world. Climate change could affect the length of growing seasons for many pollen producing plants, and increased levels of CO_² cause plants to grow more vigorously and potentially produce more pollen.

You are more likely to become sensitised to an allergen the longer you are exposed to it so with more plants producing more pollen over longer periods of time it is highly likely we will see incidences of pollen related allergic disease rise.

Dr Iain Lake, the lead researcher on the project, said: “Until now it hasn’t been known what sort of an impact climate change will have on pollen allergy – already a major public health problem.

Our work forms one of the first studies to predict what the consequences of climate change on pollen allergy may be.

Invading allergens

The research team focused their efforts on common ragweed (Ambrosia artemisiifolia), investigating plant distribution, productivity, pollen production and dispersal and the resulting allergy impacts across Europe.

The work was carried out as part of the EU-funded ‘Atopica’ project, which sought to understand how climate, land use and air quality changes will impact human health. The team of scientists decided to look at ragweed because of the high rate at which it is spreading through Europe and the high frequency at which Europeans are becoming allergic to it.

The ragweed species was first observed in the mid 19^th century and has since spread rapidly, progressively exposing more and more people to its highly allergenic pollen. Methods to control the plant are intensive and costly.

Ragweed is a highly invasive plant and its pollen is a common allergen: a single plant may produce around a billion grains of pollen per season which are carried on the wind with high potential to cause allergies.

Longer seasons of discontent?

The team created maps of estimated ragweed pollen counts over the pollen season and combined them with data on where people live and levels of allergy in the population.

Researchers found that the number of people suffering hay fever from ragweed pollen could double from 33 to 77 million people by as soon as 2050, believing climate change will be responsible for two thirds of this increase.

Higher ragweed pollen concentrations and a longer ragweed pollen season may also increase the severity of ragweed symptoms, with populations across most of Europe likely to be affected.

"Our research shows that ragweed pollen allergy will become a common health problem across Europe, expanding into areas where it is currently uncommon."

- Dr Iain Lake

According to the scientist’s projections, incidences of sensitisation will increase in countries with an existing ragweed problem such as Hungary or the Balkans but the greatest proportional increases will happen where sensitisation is now relatively uncommon, for example in Germany, Poland or France.

"Higher ragweed pollen concentrations and a longer ragweed pollen season may also increase the severity of symptoms," Dr Lake said. "France and the north west of Italy are likely to see airborne ragweed pollen earlier in the season from mid-July to mid-August. Our projections suggest that ragweed pollen will persist from mid-September to mid-October across most of Europe."

"The annual economic burden of allergic disease in the EU is already estimated at between €55 billion and €151 billion so increases on this level will bring a hefty price tag."

What’s the forecast?

Scientists believe that the control of ragweed is important for public health and as an adaptation strategy against the impacts of climate change.

Dr Lake suggests that "whilst very rapid plant invasion could increase the amount of people affected to around 107 million, improved management strategies could reduce the amount of people affected to about 52 million."

"It is important to add that climate change consequences will not be restricted to ragweed" Dr Lake urges. "A range of other pollen-producing species are likely to be affected. Our methods provide a framework for investigating the impacts of climate change on pollen allergy for other species."