Why worry about VOCs?

Question

Why should we be worried about the production of volatile organic compounds (VOCs) when trees have been emitting them for millions of years?

homework question...need a good answer

Answer 1

Each VOC is a unique chemical and will enter chemical reactions in a fashion unique to that chemical. Trees emit large amounts of VOCs especially isoprene and terpenes. However, these particular VOC's are not important air pollutants themselves. NO2 reacts with some VOC's to form ozone. NO2 is itself a man made pollutant and was not common in the atmosphere prior to the widespread use of internal combustion engines by humans.

You make an important point as well. The VOC's that trees emit have been part of the environment for millions of years and life has evolved to tolerate these chemicals. On the other hand common artificial VOCs such as paint thinners, dry cleaning solvents, and some constituents of petroleum fuels have only become common over the past 100 years or so. Evolution has not had the time required to adapt life to these chemicals nor their byproducts such as tropospheric ozone.