Treated wood waste

Chromated copper arsenate (a combination of chromium, copper, and arsenic) is one of the most common chemical formulations found in treated wood. Specific uses and disposal of this type of treated wood have raised safety issues, primarily because of arsenic.

Coal tar creosote is the most widely used wood preservative in the United States. Creosote is the name used for a variety of products (wood creosote, coal tar creosote, coal tar, coal tar pitch, and coal tar pitch volatiles). These products are mixtures of many chemicals created by high-temperature treatment of beech and other woods, coal, or from the resin of the creosote bush.

Creosote-treated wood is a source of polycyclic aromatic hydrocarbons (PAHs). 

Pentachlorophenol was once the most heavily used pesticide in the United States. It was used as a biocide and wood preservative. It's now only used on power-line poles, railroad ties, cross arms, and fence posts. 

As of 2022, the Environmental Protection Agency (EPA) banned further use of pentachlorophenol due to the health risks this chemical poses to workers.

Arsenic (and lead)

Exposure to large amounts of arsenic can lead to serious illness or death. Ongoing exposure to smaller amounts over a long time can cause many different adverse health effects.

The EPA has also found that arsenic-treated wood is often contaminated with lead.

Chromium metal

Exposure to chromium metal (Cr) can be harmful to the skin, eyes, blood, and respiratory system. Potential health effects depend on dosage and routes of exposure.

Copper

Small amounts of copper are necessary for good health. However, large amounts can cause dizziness, headaches, abdominal cramps, and liver and kidney damage. Copper is also toxic to salmon and other fish.

Pentachlorophenol

Exposure to pentachlorophenol happens mostly to workers at lumber mills and wood-treatment facilities. Pentachlorophenol can harm the liver, kidneys, blood, lungs, nervous system, immune system, and gastrointestinal tract. It can also irritate the skin and eyes.

As of 2022, the EPA has banned pentachlorophenol due to the health risks this chemical poses to workers.

The only type of treated wood you can burn is creosote-treated wood, and you may only burn creosote-treated wood in a commercial or industrial incinerator or boiler in accordance with state and federal regulations.