Birch trees now asthma villains
Christchurch mum Genevieve Radley knows all too well the health problems silver birch trees can cause.
For two years she rented a house in Springfield Rd, St Albans, which had a huge, old protected silver birch tree planted directly outside it. She suffered from poor health throughout her stay there.
"I needed two asthma inhalers and a nose antihistamine spray just to survive and breathe easily. My eyes were constantly streaming and itchy."
A scratch-test done by Radley's GP confirmed her suspicions the towering silver birch outside her property was at the root of her health problems and she eventually moved, but the months of constant irritation left her sinuses permanently damaged.
Bruce Knapp lives two doors down from a large silver birch tree and suffers from a persistent cough. When he goes on holiday the cough magically disappears, but as soon as he is back home it returns.
"I would love to have it [the silver birch] cut down so I could stop using my inhaler," Knapp told The Press.
Christy Ballantyne "literally did a happy dance" when her neighbours cut down their silver birches. She suffers from Oral Allergy Syndrome, a condition in which birch pollen and proteins from some fresh fruits, such as apples, cross-react, prompting an allergic reaction.
"The allergy is beyond your normal hay fever. It means I have to avoid silver birch trees, take strong antihistamines and limit diet during the hayfever season," Ballantyne explained.
The trio are among many allergy sufferers in Christchurch who can relate strongly to Canterbury rugby boss Hamish Riach's four-year battle to get the silver birches outside his Merivale home chopped down because of their detrimental impact on his family's health.
For them the exotic silver birches that can be found in many Christchurch streets, parks and gardens are an unwelcome addition to the landscape and a source of suffering.
But are they right to blame the humble silver birch for their ills?
According to University of Otago respiratory medicine and allergy expert Professor Julian Crane very little research has been done in New Zealand on birch pollen levels and how they impact on people's health, but birch pollen did appear to trigger hay fever and asthma in some people.
"Pollens can cause lots of symptoms and problems in the season," Crane said. Nasal problems were common among those with allergies to birch pollen, but they could also suffer from respiratory problems.
"Not all people with hay fever will also have asthma but they do commonly go together. When people do suffer from both they often find that when their hay fever flares up, so too does their asthma," Crane said.
Canterbury Medical Officer of Health Dr Alistair Humphrey said silver birch trees were known to cause allergies "slightly more frequently" than other trees, but the removal of silver birches on public land was unlikely to reduce the overall burden of allergic reactions as so many silver birches existed on private property.
Allergic reactions could be very debilitating but they were hardly ever lethal.
"Our best evidence suggests that grass allergy remains the major cause of respiratory allergic reactions in Christchurch," Humphrey said
Poor air quality caused by wood fires killed more people than either grass allergy or silver birch pollen.
But Lincoln University Emeritus Professor Ian Spellerberg is convinced silver birches are a menace and should be removed from urban environments.
"Some tree species are not suitable for urban environments for all kinds of reasons. That includes silver birch because, of all trees in New Zealand, silver birch pollen is the main cause of allergic symptoms including hay fever, asthma and food allergies," said Spellerberg.
It was frustrating that despite the wealth of evidence pointing to the health problems caused by silver birches, the trees were still widely found in public places.
"What makes me particularly concerned is whenever I see silver birches in school playgrounds. It's one of the worst scenarios we could have because we know what the dangers of silver birch pollen are," Spellerberg said.