Sentence:  Surprisingly, this analysis revealed that acute exposure to solvent vapors at concentrations below those associated with long-term effects appears to increase the risk of a fatal automobile accident. Furthermore, this <WSD>increase</WSD> in risk is comparable to the risk of death from leukemia after long-term exposure to benzene, another solvent, which has the well-known property of causing this type of cancer. 
Meaning of the word marked with <WSD> tags:  An amount by which a quantity is increased.