The U.S. EDA Data

Creosote is a wood preservative used for commercial purposes only it has no registered residential uses. 

Creosote is obtained from high temperature distillation of coal tar (itself a mixture of hundreds of organic substances). Over 100 components in creosote have been identified. It is used as a fungicide, insecticide, miticide, and sporicide to protect wood and is applied by pressure methods to wood products, primarily utility poles and railroad ties. This treated wood is intended for exterior/outdoor uses only. Its commercial uses include railroad ties (70%), utility poles (15-20%), and other miscellaneous commercial uses (10-15%). 

Creosote penetrates deeply into and remains in the pressure-treated wood for a long time. Exposure to creosote may present certain hazards. Creosote is a possible human carcinogen and has no registered residential uses. Therefore, precautions should be taken both when handling the treated wood and in determining where to use the treated wood. It should be noted that such exposure usually occurs only when one comes in contact with railroad ties and/or utility poles. 

MICROBIAL DEGRADATION OF WOOD-PLASTIC COMPOSITE MATERIALS 

Unlike wood, composite materials do not need to be dipped or pressure-treated for preservatives, or biocides, to be easily incorporated into their matrix. Biocides as pellets or powder are mixed with other ingredients, compounded, and extruded into shapes. 

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