Junk Science Targets Backyard Decks

Published June 1, 2003

If you are considering a new deck for your home, act fast. Federal regulators are poised to ban the most popular and affordable decking material: wood treated with the preservative chromated copper arsenate (CCA).

Junk science has indicted CCA, despite the fact that consumers and builders have safely used CCA-treated wood for decades because it resists rotting and pests.

A Consumer Product Safety Commission (CPSC) report released in February claims CCA-treated wood isn’t safe for children because it contains trace levels of arsenic. And the CPSC claims arsenic exposure in childhood might increase lifetime cancer risks for lung or bladder cancer, which occur late in life.

CPSC based its conclusions on two National Research Council (NRC) reports (1999 and 2001), on which the Environmental Protection Agency (EPA) based a drinking water rule. The NRC assessed risks based on studies of Taiwanese populations exposed for decades to relatively high levels of arsenic in drinking water. CPSC assumed that if long-term exposure increases risk, then short-term exposure does the same.

Not All Exposures Equal

CPSC assumed exposure to arsenic for a few years in childhood is equivalent to the same total exposure evenly distributed over a lifetime. The 2001 NRC report, however, concluded cancer risk increases disproportionately with years of exposure, suggesting the CPSC assumption overstates risks.

The Taiwanese data themselves present serious limitations. The researchers attempted to determine at what level arsenic poses a risk based on arsenic levels in drinking water wells. Villages included several wells, with a wide range of arsenic levels. Researchers did not know who drank from which wells, so they developed median arsenic levels for each village. Hence, a village may have reported excess cancers from one well that contained high levels of arsenic, but researchers assumed the cancers resulted from exposures at a lower median level.

Rather than take into account how these data limitations exaggerate both EPA and NRC risk estimates, CPSC moved in the opposite direction. It assumed arsenic is 6 to 56 times more potent than EPA’s risk estimates.

Do any CPSC assumptions hold up in peer review? We don’t know … because the CPSC refuses to release the results of its peer review or the data used in the study.

Junk Science Has Consequences

CPSC’s sloppy research will likely encourage local parks and recreation departments, daycare centers, and other child-focused facilities to tear out playground equipment. Perhaps wealthy communities will be able to rebuild with alternative materials, but what about poorer communities? Will kids in poor, inner-city neighborhoods be better off without safe play areas?

CPSC junk science may also advance bans on residential uses of CCA. Last year EPA announced–but has yet to finalize–plans to ban certain residential uses of the preservative, while asserting it has not found any “unreasonable risk to the public or the environment.” EPA is also considering whether to list CCA-treated wood as a hazardous waste, which could greatly increase disposal costs.

A ban on CCA will cost consumers an estimated 20 to 30 percent for wood treated with alternative preservatives … and the cost may be much higher than this estimate. In comments to EPA, one wood processor noted fence posts made with alternative products cost more than double CCA-treated posts. The alternative posts are expected to last only 10 years, while CCA-treated posts last 30.

In addition, about 350 wood processors in the U.S. would be forced to retool their shops at a very high price (up to $200,000 each) to make wood with alternative preservatives. Any small business that uses the wood will face steeper repair and replacement costs for various structures, as well as increased disposal costs.

Some users will switch to plastic lumber or hardwoods like cedar or redwood. Yet these options are prohibitively expensive for many families and communities, as they can double costs. Regulators might also want to consider whether they’re comfortable with a federal policy that encourages harvesting of redwood forests.

As prices escalate, many people may keep their old decks longer–even when they deteriorate into safety hazards. New decks constructed with alternative preservatives–which are highly corrosive to screws and nails–may also pose safety hazards. Consumers who fail to use stainless steel screws and nails may see their new decks eventually collapse.

CPSC didn’t consider these potential safety perils. In fact, it didn’t even consider whether the alternatives were more or less dangerous than CCA.

CPSC is supposed to be the nation’s consumer advocate. If CPSC officials are serious about uncovering threats to consumer safety and choice, maybe it’s time they looked in the mirror.

Angela Logomasini is director of risk and environmental policy at the Competitive Enterprise Institute.