Pressure-treated wood is no longer a simple issue due to the various chemicals being used. The main question is if the wood in question is treated with Chrominated Copper Arsenate (CCA), due to the multitude of hazards related to those specific chemicals. The Environmental Protection Agency banned the use of CCA treated lumber in residential capacities in March of 2009 and by 2013 all chemical plants need to have converted to newer chemicals for treating all lumber (mainly industrial and marine usage).
Pressure-treated wood is now treated with Alkaline Copper (AC) and Quaternary Ammonium Compounds (ACQ). These compounds are much less toxic and have shown to not leach into soils the way CCA and Creosote have. This does not eliminate health risks but significantly minimizes them.
The largest issue with health associated with ACQ pressure-treated wood is the toxicity of the wood dust. Having been permeated in chemicals that are designed to withstand water and elements, the toxic chemicals can have significant effects if large amounts are ingested or topical exposure is extreme. Wood dust not only allows for the chemicals to be inhaled but for ingestion and long term skin exposure. Repeated, chronic, or long term exposure to wood dust from pressure-treated lumber can cause significant health effects.
Ingestion of Pressure Treated Wood Dust
Though the ingestion of pressure-treated wood dust is rare, and the ingestion of the chemicals in large enough doses rarer still, it is important to never eat, smoke, drink or consume any products in the areas surrounding a working project. Ingestion of wood dust can cause permanent damage to the stomach, digestive tract, intestines, liver, and kidneys. The average consumption of pressure-treated wood dust usually results in extreme abdominal discomfort and mild intestinal issues.
Skin Exposure to Pressure Treated Wood Dust
Copper is a highly corrosive substance, this combined with the alkaline can make for a large degree of skin irritation when in contact with not only the wood dust but also prolonged skin exposure to the wood itself. The Boric Acid used to temper the wood during treatment can be absorbed into the skin causing serious sensitivities and allergic reactions. Monoethanolamine is another chemical used in the treatment of ACQ wood which can be absorbed through the skin and cause highly corrosive reactions. Didecyldimethylammonium chloride is a chemical used in the Quaternary Ammonium Compounds which has shown to be permanently harmful to both the eyes and skin of animals due to its caustic nature.
Inhalation of Pressure Treated Wood Dust
Inhalation of wood dust which has been permeated with ACQ chemicals can result in extreme inflammation. Repeated exposure can cause permanent irritation to the bronchial tubes resulting in asthma, greater likelihood of upper respiratory tract infection, or prolonged colds. In some cases, bronchitis can become chronic even after exposure to the dust is minimized. Monoethanolamine is a highly corrosive substance which if inhaled in larger quantities can create damage to the lungs and nervous system. Didecyldimethylammonium chloride is dangerously caustic in significant doses and can scar lungs, throat, and cause ongoing respiratory issues.