White Paper Exposure To Arsenic In The Diet Presents A Greater Risk To Human Health Than CCA-Treated Wood

Transcription

1 White Paper Exposure To Arsenic In The Diet Presents A Greater Risk To Human Health Than CCA-Treated Wood I. Background Chromated copper arsenate (CCA) is a wood preservative that protects wood against deterioration due to termites and fungal decay. CCA was invented in 1933 and has been used extensively since the mid 1970s. Since the preservative is a pesticide, its production and use have been regulated by the U.S. Government for over sixty years, first by the U.S. Department of Agriculture, with which CCA was registered in the 1940s, and then by the Environmental Protection Agency (EPA), which was created 1970 and took over the responsibility for pesticide regulation. EPA, which has reviewed the safety and effectiveness of CCA since 1970, has not at anytime determined that CCA-treated wood poses an unreasonable risk to human health and the environment. In fact, in February 2001 EPA said: EPA has not concluded that CCA-treated wood poses unreasonable risks to the public for existing CCA-treated wood being used around homes or from wood that remains available in stores. EPA does not believe there is any reason to remove or replace CCAtreated structures, including decks or playground equipment. EPA is not recommending that existing structures or surrounding soils be removed or replaced. On May 11, 2005, EPA reiterated that it does not recommend that existing structures or surrounding soils be removed or replaced. The U.S. Consumer Products Safety Commission (CPSC) has also looked at the safety of CCA-treated wood and similarly found that no regulatory action was necessary or appropriate with respect to existing structures. II. The Level Of Arsenic Exposure From CCA-Treated Wood Is Significantly Lower Than Daily Exposures From Background Sources Such As Food And Drinking Water Arsenic is a naturally occurring element - found in soil, food and water. Studies have established that the level of arsenic exposure from CCA-treated wood is significantly lower than the levels adults and children are exposed to each day from background sources such as food and drinking water. For example, a recent study from the University of Alberta found that the maximum amount of arsenic on children s hands from playing on a CCA-treated wood playset was less than 4 µg, which is significantly lower than the average daily intake of arsenic from water and food.

2 When compared over a lifetime, the level of exposure from CCA-treated wood becomes even less significant: Mean Lifetime Exposure to Arsenic from CCA-Treated Wood vs. Diet and Drinking Water 6 Inorganic Arsenic Intakes (µg/day) Normal Background Levels From Diet & 1 Drinking Water Playsets & Decks Playsets Playsets (EPA Estimate) (CPSC Estimate) (Actual) Sources (1) Yost, L.J. et al Estimation of dietary intake of organic arsenic in U.S. children. Human and Ecological Risk Assessment 10: (2) EPA A probabilistic risk assessment for children who contact CCA-treated playsets and decks. Draft Preliminary Report. (3) CPSC Staff Report (2003). (4) Kwon E., Zhang H., Wang Z., Jhangri G., Lu X., Fok N., Gabos S., Li X., Le, X Arsenic on the Hands of Children after Playing in Playgrounds. Environmental Health Perspectives, 2004 Oct: 112(14): Thus, when using actual data from a study conducted on playsets, the lifetime level of arsenic exposure from CCA-treated wood is over 200 times less than that from diet and drinking water. The CPSC came to a similar conclusion in its review of CCA-treated wood in 2003: Over a lifetime, arsenic exposures from food, especially certain foods such as rice, other grains and meats; drinking water; and other sources could be much larger than exposures from playground equipment during childhood. Moreover, there is no evidence to suggest that typical background exposures have resulted in adverse health effects, as discussed more fully below

3 III. No Adverse Health Effects Are Associated With Exposure To CCA-Treated Wood The reports and studies discussed below, from a wide range of scientific and medical sources, offer compelling evidence that no adverse health effects are associated with exposure to CCA-treated wood. A. A Recent UC Davis Study Found No Increase in Arsenic Associated Cancers from the Use of CCA-Treated Wood A study recently completed by Dr. Daniel West of the Department of Pediatrics at the University of California-Davis (West et al., 2004) concluded that: the incidence of cancer known to be associated with arsenic exposure is either unchanged or decreased in age groups that would have been exposed to CCA-preserved wood structures during childhood. The rate of arsenic-related cancers has been the same or decreasing over the time in which CCA preserved wood has been sold in the United States. Thus, these data provide preliminary evidence suggesting that there has not been an increase in arsenic associated cancers during the period of extensive use of CCA-preserved wood in the United States. B. A Panel of Florida Physicians Found No Demonstrated Risk from Exposure to CCA-Treated Wood The Florida Department of Health appointed a panel of six physicians to investigate the issue of CCA-treated wood playground equipment. On June 14, 2002, a report was submitted by the panel. The report stated that: The available data have not demonstrated any clinical disease associated with arsenic exposure from this use of the CCA-treated wood. In addition, there have been no reported clinical cases of arsenic-induced manifestations that would be concordant with an excessive exposure to arsenic contaminated soil resulting from use of CCA-treated wood at playground and recreational facilities. Used since the 1960s, CCA-treated wood has never been linked to skin diseases or cancer in children exposed during recreational use. the Physicians Arsenic Work Group agrees with and supports the United States Environmental Protection Agency's directive that "EPA does not recommend consumers replace or remove existing structures made with CCA-treated wood or the soil surrounding those structures." - 3 -

4 C. Studies on Elevated Arsenic Levels Levels That Far Exceed Those That Could Potentially Come from Exposure to Treated Wood Find No Evidence of a Meaningful Increased Risk of Lung or Bladder Cancer The best available data from studies of U.S. and European populations exposed to elevated arsenic levels in drinking water - levels far exceeding those that could potentially result from contact with CCA-treated wood - show little or no evidence of increased risk of lung and bladder cancer. Lamm, et al. (2003). The Lamm statistical analysis demonstrates that there is no increase in bladder cancer risk from drinking water from wells that contained less than about 300 µg/l (Lamm et al., 2003). Chen et al (2004). This recently published analysis of the dose-response relationship between ingested arsenic and lung cancer as well as the impact of smoking in Taiwan shows that at arsenic exposure concentrations of µg/l there is no increased risk for developing lung cancer. This additional analysis demonstrates that when exposure and cancer risk are properly stratified, lung cancer incidence is only elevated at arsenic concentrations much higher than 100µg/l. Bates et al. (2004). The data in this paper demonstrate no increased risk of bladder cancer at drinking water exposures under 200 µg/l and then only in cigarette smokers. Steinmaus et al. (2003) found no increase in bladder cancer risk associated with arsenic in drinking water except for a group of smokers exposed at greater than 200 µg/l. Lamm et al. (2004) found no increase in bladder cancer mortality at drinking water arsenic exposures of up to 60 µg/l. This study observed 133 counties in 26 states for 30 years for a total of 75 million person-years of observation. Tollestrup et al. (2003) followed a cohort of over 3,000 children (aged 2 to 14) who lived in close vicinity to the ASARCO Ruston copper smelter between the years 1910 and The cohort was evaluated for an association between arsenic exposure and cause of death, occurring 30 to 80 years after exposure. The authors used the number of years lived in a one- mile radius (i.e., designated categories of 0- < 1.0 year, years, years, and >10 years) of the smelter stack as a surrogate for arsenic exposure. Earlier studies reported that urinary arsenic concentrations in the children living in close proximity to the smelter averaged 81 µg/l, and roughly correlated with distance from the smelter, indicating relatively high arsenic exposures (Polissar et al., 1990; Harter et al., 1993; Milham, 1978). The study found no evidence of increased bladder or lung cancer mortality rates, even in the three highest arsenic exposure categories. Additionally, in a separate study - 4 -

5 conducted in the same area, no evidence of increased lung cancer risk was identified in women living in proximity to the smelter (Frost et al., 1987). Thus, recent studies conducted in the US (e.g., Bates et al., 2004; Lamm et al., 2002; and Steinmaus et al., 2003) find no dose-response relationship between arsenic concentrations in drinking water and cancer mortality, even when exposure is above typical US levels. Furthermore, studies conducted outside the US, such as in Taiwan, where exposures are significantly higher, show no evidence of increased cancer mortality until arsenic concentrations reach several hundred micrograms/liter - levels far exceeding those that could potentially result from contact with CCA-treated wood. IV. The CPSC And EPA Risk Assessments On CCA-Treated Wood Do Not Incorporate The Latest Science EPA and CPSC have both performed preliminary risk assessments on CCA-treated wood, but those assessments were performed prior to much of the recent science on CCA and arsenic. The EPA preliminary risk assessment for existing CCA decks and play structures is based upon the National Academy of Sciences Report in Similarly, the CPSC s preliminary risk assessment was performed in Since that time, several new studies have been published which indicate that the CPSC and EPA risk assessments significantly overstate the risks of CCAtreated wood exposure. For example, Dr. Kwon of the University of Alberta and others measured the levels of arsenic residue on children s hands following play on CCA-treated wood playsets, and found the residue levels to be approximately times less than the exposure estimates used in the CPSC and EPA preliminary risk assessments. (Kwon et al., 2004). These data are significant because cancer risk values are calculated from exposure values, and the lower the exposure estimates the lower the potential risk. In addition, recent studies conducted to examine the bioavailability of the arsenic removed from treated wood structures clearly demonstrate that less than 50% of the arsenic ingested is absorbed. The CPSC preliminary assessment, however, assumed a default value of 100% because it did not have this data. If the CPSC had instead used the 50% bioavailability data, the level of arsenic exposure from CCA-treated wood structures would have been approximately 5-10 fold less than from dietary sources. Furthermore, recent peer reviewed and published reports suggest that the cancer potency values for arsenic used in the EPA and CPSC preliminary risk assessments significantly overestimate the toxicity of the element. (e.g., Bates et al., 2004; Lamm et al., 2002; and Steinmaus et al., 2003). The new data demonstrate that there is no evidence to indicate that there is an increased incidence of cancer until arsenic concentrations reach levels far exceeding those that could potentially result from contact with CCA-treated wood. Thus, EPA and CPSC s preliminary risk assessments are out of date, and they likely overstate risk by a significant margin

6 V. Conclusion In summary, studies have established that people are exposed to greater levels of arsenic from food and drinking water each day than from exposure to treated wood. In addition, two federal agencies have assessed the safety of CCA-treated wood and found that no regulatory action is necessary. Seventy years of safe use and the body of scientific and medical evidence demonstrate that CCA-treated wood is safe when used as recommended. References Baraj, L Exponent: Summary of CCA Exposure Analyses Using Data From the University of Alberta Study. Bates MN, Rey OA, Biggs ML, Hopenhayn C, Moore LE, Kalman D, Steinmaus C, Smith AH Case-Control Study of Bladder Cancer and exposure to Arsenic in Argentina. Am. J. Epidemiol.; 159(4): Chen, C.L. et al Ingested Arsenic, Cigarette Smoking, and Lung Cancer Risk, A Follow- Up Study in Arseniasis-Endemic Areas in Taiwan, JAMA (24), Frost, F., Craun, G., Brown, K.G Detection of excess arsenic-related cancer risks. Environ. Health Perspect. 110(1), A12. Kwon E., Zhang H., Wang Z., Jhangri G., Lu X., Fok N., Gabos S., Li X., Le, X Arsenic on the Hands of Children after Playing in Playgrounds. Environ. Health Perspect., 112(14): Lamm SH, Byrd DM, Kruse MB, Feinleib M, Lai S Bladder cancer and arsenic exposure: differences in the two populations in the SW Taiwan study. Biomedical and Environ. Science 16: Lamm SH, Engel A, Kruse MB, Feinleib M, Byrd DM, Lai S, Wilson R Arsenic in Drinking Water and Bladder Cancer Mortality in the United States: An Analysis Based on 133 U.S. Counties and 30 Years of Observation. J Occup. Environ. Medicine; 46(3): Michaud DS, Wright ME, KP Cantor, PR Taylor, Virtamo J, Albanes D Arsenic Concentrations in Prediagnostic Toenails and the Risk of Bladder Cancer in a Cohort Study of Male Smokers. Am. J. Epidemiology, 160: Steinmaus C, Yuan Y, Bates MN, Smith AH Case-Control Study of Bladder Cancer and Drinking Water Arsenic in the Western United States. American Journal of Epidemiology 2003;158: Tollestrup, K, Frost, F.J., Harter, L.C., McMillan, G Mortality in children residing near the ASARCO copper smelter in Ruston, Washington. Environ. Health, 2003 Nov: 58 (11):

7 West, D Health Effects Of Preserved Wood: Relationship Between CCA Treated Wood And Incidence Of Cancer In The United States. Unpublished report, U.C. Davis Medical School, Dept. of Pediatrics