Alternative heavy-duty preservatives include creosote and pentachlorophenol. Tar, creosote, and disinfectant kept the smell down. Polycyclic aromatic hydrocarbons are primarily found in natural sources such as creosote. Longer exposure to creosote vapours can cause irritation of the respiratory tract. The vegetation consists mostly of black sagebrush and creosote bush. The simple phenols are not the only active element in wood-tar creosote. This chemical is a product of creosote, a type of tar. The native vegetation is dominated by high and low desert shrubs such as creosote bush. Later poles were treated instead with creosote or copper sulphate for the preservative. Deterrents such as creosote, diesel oil, or ammonia can be used. Many native species have been replaced with creosote shrubs. The following reactions are alkylations of soluble compounds found in creosote preservatives with methanol. These animals now contain concentrations of hazardous chemicals which were secreted from the creosote. Traced southward the depressions increase to ~5 m in width with scattered creosote shrubs. Certain species of aquatic organisms are affected differently from the chemicals released from creosote preservatives.