Risk Policy Report, Adam Sarvana
Published June 11, 2007
An environmental group is pushing EPA to release a controversial agency-funded study on whether children may be exposed to arsenic-based wood preservatives that are tracked into homes from porches, decks and other structures, an issue that could help define the scope of industry liability, activists say.
If walking on arsenic-treated wood is found to lead to tracking the substance indoors, it could present a potential risk to children who play on floors and frequently put their hands in their mouths, according to a spokesman for the Environmental Working Group (EWG) and a letter sent to EPA by the group and obtained by Risk Policy Report.
The findings could be an important test of the treated wood industry’s potential liability for childhood exposures to inorganic arsenic, which is listed as a known carcinogen by EPA and the National Toxicology Program.
However, industry consultants familiar with the study say it has methodological shortcomings and should not be considered a finished product. One consultant, who has seen a draft of the study, says it “may be of academic interest, but I don’t know if it’ll change EPA’s regulatory decisions.” The source says the version of the study he reviewed last year failed to take existing arsenic exposure literature into account or put the findings in context, such as by discussing its finding that the amount of arsenic found on treated deck wood did not strongly correlate with the amount found in tested carpet samples.
A source with EWG says the group has been told the reportedly finished study -- which assesses the potential for tracking arsenic indoors after contact with a wood treatment chemical known as chromated copper arsenate (CCA) -- may not be released by EPA. In its May 31 letter, EWG asks James Gulliford, EPA assistant administrator for the Office of Prevention, Pesticides & Toxic Substances, to “immediately make public the results of this work so that parents can take the appropriate actions to protect the health of their children.” The letter is available on InsideEPA.com.
CCA was phased out by industry in 2003, but EPA estimates that roughly 70 percent of homes nationwide still have arsenic-treated wood decks and porches, according to the EWG letter. It was mostly used to protect wood from rotting due to insects and microbial agents.
The EWG source says the agency should release the new study and let a debate about the results take place in public. “If there’s no liability, then industry has nothing to fear,” the source says. “We’re for having the objective science out there and letting the chips fall where they may. If there’s no reason [for the industry] to compensate for new [non-treated] decks, fine, but it’s not EPA’s job to hide science.”
The source says the question of industry compensating consumers for replacement of treated decks and structures “should at least be on the table. Not litigation, but compensation. We’re neither for nor against litigation on this issue.” A “good result” of releasing the study, the source says, would be “honesty about the risks of arsenic-treated decks. . . . Right now we’re at ground zero with absolutely nothing happening, no information out there.”
But a second industry consultant familiar with the issue says the study should be dismissed, calling its methodology “enormously open to question” and saying EPA publicizing the results as an agency product “would be the height of irresponsibility.” The indoor exposure risk from dislodged wood fibers coated with CCA “is dwarfed by the amounts we get from eating and drinking,” the source says. “Among the risks we should be worried about, it’s not even in the top thousand.”
EPA did not respond to a request for comment, and it is unclear when or whether the study will be released. However, the EWG source says the issue deserves examination and public scrutiny because arsenic’s ability to get on peoples’ hands when they touch treated wood “is rock solid”and suggests a similar risk exists for tracking it indoors.
A third industry consultant, who is not connected to the study, says key issues it should address in order to be valid include looking at an increase over background arsenic levels in homes with CCA-treated decks versus nearby homes without treated decks; focusing on indoor rooms immediately adjacent to outside decks to accurately assess sites where increased arsenic levels are most likely; and whether the indoor arsenic is attached to wood fibers, rather than coming from arsenic dust likely originating elsewhere. “From this kind of study you could [accurately] determine [indoor arsenic] levels with decks and without decks,” the source says.
The EWG source, who is not familiar with the study design, says the report may not show a significant increase from tracking CCA arsenic indoors. “We don’t know what it shows. It might show a million different things.” The bottom line, the source says, is “we think it’s done and we’d like to see it. . . . If we’re going to criticize the methodology let’s get the study out there and do it in public.”
Meanwhile, a panel of EPA’s Science Advisory Board (SAB) reviewing EPA’s arsenic cancer risk assessment is preparing to release a final report as early as this month that will likely support further research on the substance’s health effects while backing a study EPA used to develop its strict drinking water standard.
At issue is a draft report, Advisory on EPA’s Assessments of Carcinogenic Effects of Organic and Inorganic Arsenic, originally released by an SAB panel last October, that affirms the conclusions of a controversial Taiwanese study EPA used to support its arguments in 2001 when the agency tightened its drinking water standard for arsenic to 10 parts per billion (ppb).
The final version of the report will likely inform the agency’s future regulations because it will influence risk assessments provided in EPA’s Integrated Risk Information System, which the agency and state officials use in regulatory decision-making. The report will also be a factor in child health risk assessments for the wood preservatives industry, an industry source says.
The draft report backs the findings of the epidemiological study conducted in Taiwan that indicates a linear, cause-and-effect relationship between exposure to inorganic arsenic in drinking water and serious illnesses, such as bladder cancer. The study allowed EPA to justify its 10-ppb standard.
In the draft, the SAB panel says it supports the agency’s use of a linear model as recommended by the National Research Council for inorganic arsenic and that “the Taiwanese data set remains the most appropriate choice for estimating cancer risk in humans.” The report adds that there “is not sufficient justification for the choice of a specific, nonlinear form of the dose-response relationship,” which would indicate there is an exposure threshold below which arsenic does not present a cancer risk.
The second industry consultant says the SAB panel’s report will likely be released this month and will endorse the Taiwanese study as “the single best data set despite its flaws,” but will recommend that it not be solely relied upon in setting future risk standards. The source says the report will suggest EPA include more recent studies conducted in the U.S. and South America that “tend to indicate there is a threshold below which arsenic is safe,” but adds, “it’s not exactly clear how that will be done.”
The source says some panel members will likely say in the report that arsenic’s mode of action, or method of interacting with the body, is not well understood, and that EPA should therefore use a linear or non- threshold model as a default as outlined in the agency’s 2005 cancer assessment guidelines. “Politically the least difficult way out is for EPA to default to the linear model,” the source says. However, “I don’t think that’s what we’ll be talking about five years from now. Everything I’ve heard says we’re moving away from traditional [linear model] thinking” on arsenic, the source says.
An SAB source says the study “is getting close to being done” but could not give an exact timeline. -- Adam Sarvana
-- Adam Sarvana (703) 416-8516 Fax (703) 416-8543 Associate Editor, Risk Policy Report Inside Washington Publishers
