Those two findings are coherent and both, taken together, add more weight to conclusions drawn from either taken separately. Exposure pathways are the various routes by which a risk agent may travel through an environmental system to reach an individual. They result in a state of the environment. Intake pathways are the various routes by which the risk agent can enter the body once the state of the environment has been established. The major ones are ingestion, inhalation and dermal absorption.
Variability refers to the actual variation of exposure conditions, intake, etc, in a population.
It is a characteristic of the situation. Uncertainty refers to the lack of complete confidence in characterizing this variability. In an exposure assessment, I may want to know how a the environmental state varies across a population so I can look at the degree of risk equity in that population. I may also want to characterize the uncertainty in my claim that no individual has an exposure above some level. I would use these to determine the epistemic status of any claims made in exposure assessment.