Last year, after federally mandated health-related changes to pressure-treated wood's formula, a new recipe proved corrosive to metal connectors.

Federal studies have since found no unreasonable risk from the original formula and that adequate sealants can further reduce any potential for adverse health effects.

At question was chromated copper arsenate (CCA), a fertilizer compound that also had been used to keep pressure-treated wood from rotting since the 1970s. Unfortunately, along with copper and chromium, the compound also contained arsenic, a known human carcinogen.

Readily available at big box warehouse outlets like Home Depot, Lowe's and other hardware and construction material retailers, pressure-treated wood products are commonly used in many outdoor applications, including children's play structures, decks, walkways and fences.

After the industry voluntarily bowed to pressure from health and safety officials, replacement preservatives included applications of ammoniacal copper quat, or "ACQ," copper azole and borate -- a new recipe that proved more corrosive to metal than the old formula.

That's of particular concern in hurricane, earthquake and other regions where a home's structural integrity is paramount. Pressure-treated wood also has long been commonly used to provide a base or sill plate for a home's framing. The framing is attached to the base with metal connectors and fasteners.

Experts say well-coated galvanized metals, including zinc coated products give greater protection than uncoated metals, but stainless steel is best used with the new engineered wood products because stainless doesn't corrode.

That takes care of potential structural problems.

But this month, in it's ongoing research, the Environmental Protection Agency said it "has not concluded that CCA-treated wood poses any unreasonable risk to the public or the environment."

Given arsenic's known status as a carcinogen, however, any lessened use of the toxin is desirable, the EPA reported. In use since the 1970s, dimensional lumber used in home building treated with CCA has been illegal since December 31, 2003.

Now, after one year of interim studies that began in 2003 and are scheduled for completion later this year, the EPA, along with the Consumer Product Safety Commission (CPSC) found that properly sealing the outlawed pressure-treated wood would help keep arsenic from dislodging. Given the EPA found no "unreasonable risk" in CCA-treated wood, sealing it should render it even more harmless.

The EPA study is evaluating 12 commercially available products, both paints and stains on outdoor "mini-decks" comprised of older CCA-treated wood at Research Triangle Park, NC. The CPSC study in Gaithersburg, MD is examining eight stains and sealants (most of which are the same as those tested by EPA) on new CCA-treated wood.

In early May, the EPA said of all the coatings, "They all showed an ability to reduce exposure to arsenic, but further data is needed to identify more defined clear trends with respect to product type or characteristics."

The EPA said the tests favored non-film forming products (as opposed to paint) and the top five products were:

• Clear, water-based, acrylic tint base stain (no tint added)

• Oil-based deck toner base deck stain (no tint added)

• Semi-transparent, oil-based, sealant with UV blocker

• Clear, oil-based penetrating sealant with alkyd and acrylic

• Clear, oil-based, acrylic stain

The EPA is currently concerned that paints (film-forming coatings) used on exposed outdoor surfaces are subject to chipping or flaking. Removing paint by sanding or power washing, to prep the surface for a new coat, could also increase the potential for exposure to arsenic. An elastic vinyl product designed to encapsulate CCA wood, performed well, but has the same chipping potential as paint.

The EPA says a second round of studies will provide a clearer picture about the longevity of the treatments. Meanwhile, the EPA recommends an annual application of oil or water-based coatings (rather than paint) to decks or other residential components comprised of CCA-treated wood.

The Environmental Working Group, a public interest watchdog for environmental issues has long warned about CCA-treated lumber and offers online "Ten Safety Steps to Reduce Your Family's Exposure to Arsenic From Arsenic-Treated Wood."