The Acreage Cancer Study

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Welcome back! Please note, there will be no Blog postings next week (July 26-30). If there are any updates, they will be posted on the Forum. We apologize for the inconvenience.

Below are several articles that may be of interest to you. We hope you enjoy them.

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Childhood cancer and agricultural pesticide use: an ecologic study in California.

By: Reynolds P, Von Behren J, Gunier RB, Goldberg DE, Hertz A, Harnly ME.

March 11, 2002

Abstract

We analyzed population-based childhood cancer incidence rates throughout California in relation to agricultural pesticide use. During 1988-1994, a total of 7,143 cases of invasive cancer were diagnosed among children under 15 years of age in California. Building on the availability of high-quality population-based cancer incidence information from theCalifornia Cancer Registry, population data from the U.S. Census, and uniquely comprehensive agricultural pesticide use information from California's Department of Pesticide Regulation, we used a geographic information system to assign summary population, exposure, and outcome attributes at the block group level. We used Poisson regression to estimate rate ratios (RRs) by pesticide use density adjusted for race/ethnicity, age, and sex for all types of childhood cancer combined and separately for the leukemias and central nervous system cancers. We generally found no association between pesticide use density and childhood cancer incidence rates. The RR for all cancers was 0.95 [95%confidence interval (CI), 0.80-1.13] for block groups in the 90th percentile and above for use of pesticides classified as probablecarcinogens, compared to the block groups with use of < 1 lb/mi(2).The RRs were similar for leukemia and central nervous system cancers. Childhood leukemia rates were significantly elevated (RR = 1.48; 95%CI, 1.03-2.13) in block groups with the highest use of propargite, although we saw no dose-response trend with increasing exposure categories. Results were unchanged by further adjustment for socioeconomic status and urbanization.

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Childhood Cancer

United States Environmental Protection Agency

Cancer in childhood is quite rare compared with cancer in adults, but it still causes the most deaths, other than injuries and accidents, among children 0-19 years of age.47

Childhood cancer is not a single disease, as it includes a variety of malignancies. The forms of childhood cancer that are most common vary at different ages.

Cancer Incidence and Mortality

The incidence of childhood cancer increased from 1975 until about 1990. The frequency of the disease appears to have become fairly stable overall since 1990. Mortality has declined substantially during the last 25 years, due largely to improvements in treatment.

The causes of cancer in children are poorly understood, though in general it is thought that different forms of cancer have different causes. Established risk factors for the development of childhood cancer include family history, genetic defects, radiation, and certain pharmaceutical agents used in chemotherapy.47 Evidence from epidemiological studies suggests that environmental contaminants such as pesticides and certain chemicals, in addition to radiation, may contribute to an increased frequency of some childhood cancers.32 Some studies have found that children born to parents who work with or use such chemicals are more likely to have cancer in childhood.48 It may be that the chemicals cause mutations in parents' germ cells that may increase the risk of their children developing certain cancers, or perhaps the parental exposure is passed on to the child while in utero, affecting the child directly. Children's direct exposures to such chemicals also may contribute to cancer.

Childhood Cancer by Type

Trends in the total incidence of childhood cancer are useful indicators for assessing the overall burden of cancer among children. However, broad trends mask changes in frequency of individual cancers. Individual cancers often have patterns that diverge from the overall trend. Moreover, environmental factors may be more likely to contribute to some childhood cancers than to others.

Ionizing radiation, such as from x-rays, is a known cause of leukemia and brain tumors.49-50 There is suggestive-but not conclusive-evidence that parental exposures to certain chemicals may be a cause of leukemia, brain cancer, non-Hodgkin's lymphoma, and Wilms' tumor in children.51

A number of studies have evaluated the relationship between pesticide exposure and certain types of childhood cancer, and while the evidence is suggestive of a link, it is still not conclusive.47 Most studies of the relationship between pesticide exposure and leukemia and brain cancer show increased risks for children whose parents used pesticides at home or work, and for children who may be exposed to pesticides in the home.52-53 Evidence is limited but suggestive that non-Hodgkin's lymphoma in children may be linked to parental pesticide exposure and exposure to pesticides in the home.52 There is some evidence linking pesticide use to Wilms' tumor and Ewing's sarcoma.52

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Radiation Environments and Exposure Considerations for the Multi-Mission Radioisotope Thermoelectric Generator

By: Kelly, William M.; Low, Nora M.; Zillmer, Andrew; Johnson, Gregory A.; Normand, Eugene

SPACE TECH.& APPLIC.INT.FORUM-STAIF 2006: 10th Conf ThermophysApplic Microgravity; 23rd Symp Space Nucl Pwr & Propulsion; 4thConf Human/Robotic Tech & Nat'l Vision for Space Explor.; 4th SympSpace Coloniz.; 3rd Symp on New Frontiers & Future Concepts. AIPConference Proceedings, Volume 813, pp. 906-919 (2006).

The Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) is the next generation (RTG) being developed by DOE to provide reliable, long-life electric power for NASA's planetary exploration programs. The MMRTG is being developed by Pratt & Whitney Rocketdyne and Teledyne Energy Systems Incorporated (TESI) for use on currently planned and projected flyby, orbital and planet landing missions. This is a significant departure from the design philosophy of the past which was to match specific mission requirements to RTG design capabilities.Undefined mission requirements provide a challenge to system designers by forcing them to put a design envelope around ``all possible missions''. These multi-mission requirements include internal and external radiation sources. Internal sources include the particles ejected by decaying Pu-238 and its daughters plus particles resulting from the interaction of these particles with other MMRTG materials.External sources include the full spectrum of charged particle radiation surrounding planets with magnetic fields and the surfaces of extraterrestrial objects not shielded by magnetic fields. The paper presents the results of investigations into the environments outlined above and the impact of radiation exposure on potential materials to be used on MMRTG and ground support personnel. Mission requirements were also reviewed to evaluate total integrated dose and to project potential shielding requirements for materials. Much of the information on mission shielding requirements was provided by NASA's Jet Propulsion Laboratory.The primary result is an ionizing radiation design curve which indicates the limits to which a particular mission can take the MMRTG in terms of ionizing radiation exposure. Estimates of personnel radiation exposure during ground handling are also provided.

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