bioaccumulation

Bioaccumulation is the gradual buildup of chemical substances in an organism as a result of ongoing uptake from the environment or diet, with losses through metabolism and elimination being insufficient to balance intake. It often affects persistent and lipophilic compounds, such as heavy metals and certain organic pollutants. Bioaccumulation is distinct from bioconcentration, which describes uptake from water alone, and from biomagnification, which refers to increasing concentrations of a substance at higher trophic levels through feeding.

Uptake can occur via multiple routes, including gills or lungs, ingestion of contaminated food, and dermal absorption. Once inside the body, substances may be stored in fatty tissues or bound to bones, and metabolic processes may not fully break them down, leading to slow elimination. Factors influencing accumulation include the substance’s persistence, solubility, and affinity for biological tissues, as well as the organism’s growth rate and metabolic capacity.

Common examples include mercury in aquatic organisms, and organochlorines such as polychlorinated biphenyls (PCBs) and DDT. Risk assessments often use metrics such as the bioconcentration factor (BCF) and the bioaccumulation factor (BAF) to quantify uptake relative to exposure. Bioaccumulation underpins many regulatory concerns because it can extend exposure to predators, including humans.

Environmental and health implications arise from chronic exposure to accumulated contaminants, including neurotoxicity, developmental effects, and reproductive harm. Because many accumulating compounds are persistent and hard to remediate, policy measures—such as restrictions on production and releases and international treaties like the Stockholm Convention—aim to reduce environmental levels and protect wildlife and human health.