Increased carbon dioxide in the air may also lead to ragweed pollen that is stronger, or more allergenic.

空气中二氧化碳增多还可以使豚草花粉变得更强，或更具过敏性。

He and another USDA researcher, Frances Caulfield, looked at the effects that rising carbon dioxide levels were having on the production of ragweed pollen.

他和美国农业部研究员弗朗西斯·考菲尔德研究了上升的二氧化碳水平对豚草花粉产量的影响。