The materials that pressure-treated wood contains to enhance its durability and protect it from termites and other insects and fungal decay can be hazardous to your health. The old chromated copper arsenate (CCA-C) contains the oxides of chromium, copper and arsenic.
Chromium is the bonding agent that fixes the chemicals to the wood, copper is a fungicide, and arsenic is an insecticide. Water dilutes the mixture which with high pressure is forced into the lumber in a steel tank. As soon as the lumber has soaked up all the toxic soup it can hold, the excess is removed. The wood is either air or kiln dried and then shipped to lumberyards and stores like Lowe’s and Home Depot.
Because of the wetting and drying cycles, the wood is more brittle and apt to crack, check and grain-raise. Checking is cracks occurring on the ends and surfaces of lumber during drying caused by shrinkage differences between the surface and cores of the lumber. Grain-raising is when the grain of the wood is raised and results in a rough surface, appearing as thin knifelike feathers along the earlywood–latewood interface. This degradation leads to a splintered wood surface. Since southern pine is typically the base wood, its characteristics contribute to the problems.
Producers of CCA treated wood claim that with proper treatment and drying, it is relatively harmless to humans, but there are some things you need to know about safely handling CCA treated wood:
- wear gloves whenever you are carrying or moving it
- carefully wash your hands before you eat and drink, especially if you do not wear gloves
- food should not come into contact with any treated wood
- only work with it outside and wear a dust mask
- if you should get a splinter of it, immediately remove it with tweezers. Keep them in your tool box.
- never burn scraps of pressure treated wood in your stove, fireplace or campfire. Burning it releases the toxic chemicals that are bonded with the wood
- every year use a polyurethane sealant or a lacquer paint like would be used on a car.
In recent years, arsenic preservative treated wood received negative publicity and increasing pressure to eliminate it. In 2003, the treated wood products industry voluntarily transitioned from CCA to alternative preservative systems such as ACQ-C (Alkaline Copper Quat Type C), ACQ-D Carbonate (Alkaline Copper Quat Type D, Carbonate formulation), CA-B/CA-C (Copper Azole Types B and C), µCA-C (Azole biocide), SBX/DOT (Sodium Borate) and Zinc Borate preservatives. CCA-C is no longer being produced for residential or general consumer use, but is still found in industrial, highway and agricultural applications in poles, piles, guardrail posts and saltwater marine exposure locations. Some of the alternatives are more corrosive to steel and some protective coatings applied over steel than CCA-C.
Even better than pressure-treated wood, if you are building new construction and can afford to pay more, use Trex® composite decking and railing material where possible or replace old decks with Trex®. In Greenville, South Carolina, you can get Trex® at Home Depot and Lowe’s. See a long list of Trex® contractors who install Trex® in the Greenville area from BKF Builders to Pro Care Services.
The American Wood Protection Association website lists the types of treated lumber and what to use for different applications. The Forest Products Laboratory site posts papers on the kinds of stain or paint to use to protect treated wood outdoors.
Borate pressure treated wood appears to be most environmentally safe, but Trex®, being composed of a minimum of 95.4 percent recycled content, is the environmentally sound choice for decking and railing fencing. The Trex® Company is also a member of the U.S. Green Building Council.