Residential trees and allergic outcomes
Other studies on trees and allergic outcomes did not observe an
association with AR. 35,36 This contrasts with our
analysis where this association was the strongest and the most
consistent. Yet, Lovasi et al. 36 reported increased
risks of asthma and allergic sensitization in 549 7-year-old residents
of New York, which was partially in line with us. Both studies used tree
cover extracted from aerial images. Tree cover does not capture
differences between trees.
We used data from a tree registry to distinguish between allergenic and
non-allergenic trees. Our results for AR and to a lesser extent for
aeroallergen sensitization suggest that in Leipzig having any trees
close to home has about the same negative health effect as having
allergenic trees close by. This might not be the case for other study
areas. Future research might show that comparisons of findings
concerning trees and allergic outcomes are only valid between cities
with similar tree patterns, air quality and urban climate.37
No epidemiological study so far had enough information to adequately
deal with the problem that pollen loads as well as allergenic potentials
may vary between tree individuals and for the same tree individuum, also
across years. 38 For most allergenic tree species this
phenomenon has not yet been explored let alone been understood.