Bioaccumulation is the process by which an organism takes in chemicals through ingestion, exposure, and inhalation. Bioaccumulation is broken down into bioconcentration (uptake of chemicals from the environment) and biomagnification (increasing concentration of chemicals as they move up the food chain). Certain species of aquatic organisms are affected differently from the chemicals released from creosote preservatives. One of the more studied organisms is a mollusk. Mollusks attach to the wooden, marine pilings and are in direct contact with the creosote preservatives. Many studies have been conducted using polycyclic aromatic hydrocarbons (PAH), which are low molecular hydrocarbons found in some creosote-based preservatives. In a study conducted from Pensacola, Florida, a group of native mollusks were kept in a controlled environment, and a different group of native mollusks were kept in an environment contaminated with creosote preservatives. The mollusks in the contaminated environment were shown to have a bioaccumulation of up to ten times the concentration of PAH than the control species. The intake of organisms is dependent on whether the compound is in an ionized or an un-ionized form. To determine whether the compound is ionized or un-ionized, the pH of the surrounding environment must be compared to the pKa or acidity constant of the compound. If the pH of the environment is lower than the pKa, then the compound is un-ionized which means that the compound will behave as if it is non-polar. Bioaccumulation for un-ionized compounds comes from partitioning equilibrium between the aqueous phase and the lipids in the organism. If the pH is higher than the pKa, then the compound is considered to be in the ionized form. The un-ionized form is favored because the bioaccumulation is easier for the organism to intake through partitioning equilibrium. The table below shows a list of pKas from compounds found in creosote preservatives and compares them to the average pH of seawater (reported to be 8.1).
Each of the compounds in the table above is found in creosote preservatives; all are in the favored un-ionized form. In another study, various species of small fish were tested to see how the exposure time to PAH chemicals affected the fish. This study showed that an exposure time of 24–96 hours on various shrimp and fish species affected the growth, reproduction, and survival functions of the organisms for most of the compounds tested.