Aldehydes, which are present within the air as well as food and beverage sources, are highly reactive molecules that can be cytotoxic, mutagenic, and carcinogenic. To prevent harm from reactive aldehyde exposure, the enzyme aldehyde dehydrogenase 2 (ALDH2) metabolizes reactive aldehydes to a less toxic form. However, the genetic variant of ALDH2, ALDH22, significantly reduces the ability to metabolize reactive aldehydes in humans. Therefore, frequent environmental aldehyde exposure, coupled with inefficient aldehyde metabolism, could potentially lead to an increased health risk for diseases such as cancer or cardiovascular disease.Here, we discuss the environmental sources of reactive aldehydes and the potential health implications particularly for those with an ALDH22 genetic variant. We also suggest when considering the ALDH22 genetic variant the safety limits of reactive aldehyde exposure may have to be reevaluated. Moreover, the ALDH22 genetic variant can also be used as an example for how to implement precision medicine in the field of environmental health sciences.