Silver Birch (Betula pendula) Pollen and Human Health: Problems for an Exotic Tree in New Zealand

Silver birch (Betula pendula) is commonly used as a street tree in temperate climatic regions. However, the medical literature contains a wealth of reports on the health effects of pollen from silver birch. In many countries such as New Zealand, silver birch is the main tree that causes allergic symptoms, including seasonal hayfever, asthma, and other health conditions such as food allergies (the oral allergy syndrome). Exposure to pollen from silver birch is more likely to occur in cities because of the numbers of the trees and the human population density. Even if there were doubts about the extent of the problem and the costs associated with the problem, the precautionary principle should apply. The health-related problems of silver birch should be promulgated and trees should be removed.