Volunteer Water Information Network |
Arsenic in CCA Pressure-Treated LumberLumber that is treated with chromated copper arsenate to resist insect and fungal decay has been used extensively world-wide over about the past three decades for use in outdoor structures. It was recognized from the onset that arsenic would be leached from the wood over time resulting in some level of either relatively direct exposure from skin contact, or from more indirect exposure from arsenic in soil, groundwater, or surface water contamination. While arsenic was already a well recognized toxin with various chronic health effects even from low level exposure (e.g., skin lesions, cardiovascular effects, lung, skin, bladder, kidney, and liver cancers), during the mid-1990's epidemiological evidence began to surface which indicated that arsenic was a far more powerful bladder, lung and kidney carcinogen than previously believed. In response to these recent findings, many countries of the developed world including the United States, the entire European Union, Japan and Canada have either discontinued or announced decisions to phase out production of CCA-treated lumber for residential uses by mid-2004. The risk estimates of four recent studies are as follows: Roberts and Ochoa estimates 502 per million population for skin cancer only; Gradient Corporation estimates 1 per million population for skin cancer only; Sharp et al. estimates 2000 per million population for lung and bladder only; and the US Consumer Products Safety Commission estimates between 2 and 100 cases of lung/bladder cancer per million population. In a preliminary study published in the New Zealand Journal of Chemistry, researchers at EQI found from a survey using wipes of US households with CCA pressure-treated lumber that the mean arsenic wipe transfer calculated across all surface types, service ages, geographic areas, and treatment types, is 63.6 µg/100 cm2. The corresponding median arsenic transferred to wipe is 12.5 µg/100 cm2. We found that there are higher levels of arsenic associated with samples taken from the northwest, samples taken from locations receiving more sun, and samples recently treated with water-sealant, paint, stain, or other covering. We found that the water-sealants appear to work for approximately 6 months while other treatments may be effective for two years or more. We did not find any differences between arsenic levels for different ages of wood. We also used the average amount of arsenic from the survey and converted it to what would be expected to occur if a hand contacted the surface instead of a wipe. We then calculated the excess risk for lung or bladder cancer using a methodology similar to the CPSC approach for persons under various scenarios of contact with CCA lumber. For a toddler averaging 7 kg from the ages of 6 months to 18 months, playing on a deck three days per week for 40 weeks a year, making 50 hand contacts at 40 cm2 contact per day of contact we estimated the risk to be 6.6 cases per 10,000, For a young child averaging 16 kg from the ages of 3 years to 6 years, playing on a CCA playset and sometimes a deck making 30 hand contacts at 60 cm2 contact per day, 3 days a week, 40 weeks a year we estimate the risk to be 7.2 cases per 10,000. For an older child averaging 32 kg from the ages of 7 years to 13 years, playing on a CCA playset and sometimes a deck making 20 hand contacts at 80 cm2 contact per day, 2 days a week, 40 weeks a year, we estimate the excess risk to be 1.6 cases per 10,000. For a adult weighing 70 kg who has 5 hand contacts at 100 cm2 contact per day, 5 days a week, 40 weeks a year we estimate the risk to be 1 case per 10,000. To obtain a more precise estimate of risk and ways that it may be reduced, we need to have more samples. As part of this study, conducted in collaboration with the Environmental Working Group, individuals receive a low-cost test of their wood or soil and a letter explaining their results. In addition to providing the participant with information that can be used to reduce their individual arsenic risk, it also helps us to better understand the complex phenomenon of the risk from arsenic due to exposure to CCA lumber.
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