Accumulation is the gradual build-up of a chemical as a result of repeated doses or exposure, where destruction or elimination of the chemical fails to keep pace with its introduction into the body. This will result in a gradual increase in concentration in an organism, organ or tissue which may cause toxic effects that can become more marked with successive doses. Factors that can enhance accumulation include selective binding of the chemical to particular types of molecules in the body, the progressive concentration of fat-soluble chemicals in body fat, complete failure or a slowing of metabolism which would otherwise reduce the concentration of chemicals, and slow excretion.