Research note: Increasing Amb a 1 content in common ragweed (Ambrosia artemisiifolia) pollen as a function of rising atmospheric CO concentration.

Although the impact of increasing atmospheric carbon dioxide concentration ([CO]) on production of common ragweed (Ambrosia artemisiifolia L.) pollen has been examined in both indoor and outdoor experiments, the relationship between allergen expression and [CO] is not known. An enzyme-linked immunosorbent assay (ELISA) was used to quantify Amb a 1, ragweed's major allergen, in protein extracted from pollen of A. artemisiifolia grown at different [CO] values in a previous experiment. The concentrations used approximated atmospheric pre-industrial conditions (i.e. at the end of the 19th century), current conditions, and the CO concentration projected for the middle of the 21st century (280, 370 and 600 μmol mol CO, respectively). Although total pollen protein remained unchanged, significant increases in Amb a 1 allergen were observed between pre-industrial and projected future [CO] and between current and projected future [CO] (1.8 and 1.6 times, respectively). These data suggest that recent and projected increases in [CO] could directly increase the allergenicity of ragweed pollen and consequently the prevalence and / or severity of seasonal allergic disease. However, genetic and abiotic factors governing allergen expression will need to be better established to fully understand these data and their implications for public health.