Bioaccumulation is the increased concentration of a pollutant from the environment that effects the first organism in the food chain. Depending upon the pollutant, bioaccumulation can effect a human if levels of the pollutant reaches a toxic state.
For instance, if a large portion of fish in an area were contaminated by a pollutant, and the humans in that area consumed this species of fish regularly, the pollutant would negatively effect the inhabitants in that area that consumed the contaminated fish. Because pollutants in fat are retained and not excreted as easily as water soluble contaminants, the contaminated fish could cause negative heath effects.