Children, Cancer, and the Environment
Cancers of the central nervous system are the second most common form of cancer in children and the most common type of solid tumor (1). These cancers may involve both the spinal cord or brain.
Causes of these cancers are largely unknown, though some studies suggest that chemical exposures may be a cause. These cancers are most common in children under age seven (2). Boys are more likely to have central nervous system tumors than girls (3).
Brain cancers are one of the cancers that are increasing in children. From 1973 to 1994, the number of reported brain cancers in children under 15 increased 1.8% per year (3).
Some argue that the increase actually represents improved detection of the cancer, possibly through use of MRI (magnetic resonance imaging) (4, 5). Many other top scientists disagree. They rgue that the increase in cases is real because brain tumors do not go undetected, regardless of the method used (6). Moreover, the increase appears to be continuing and not leveling off (7). If part of the increase were due to improved methods that find cases earlier, one would expect to see a reduced rate later. This does not appear to have occurred.
Unfortunately, the improvements in treatments that have occurred for many childhood cancers have not been achieved for brain cancer. The proportion of cancer deaths in children due to brain cancer has doubled in the last 25 years (7). The quality of life of survivors of central nervous system cancers may also be worse than that of other common kinds of childhood cancer.
Ionizing radiation is considered an established cause of brain tumors in children (3, 8).
Other environmental agents that have been suggested as contributing to this type of cancer include pesticides, solvents, and certain compounds called N nitroso compounds that are found in cured meats such as bacon, ham, and sausages (9).
There is some evidence that exposure to pesticides may be linked to brain tumors, though only a few studies have looked at this.
· A recent review of studies that looked at pesticides and childhood cancer found that nine of the 17 studies reported increased risk of brain cancer to be associated with pesticide exposure (10). Five studies found a positive relationship that was not strong enough to be reported as being statistically significant. Three studies found no excess risk to be associated with pesticide exposure.
· A large study of cancer in the children of farmers in Norway found that children of parents who used pesticides had a three times higher risk for certain types of brain tumors (11).
· A study in Los Angeles interviewed mothers of more than 200 children with brain cancer and close to 300 controls. It reported that use of flea/tick products in the home was associated with increased risk of brain cancer, particularly for children less than five years of age. The odds ratio was 1.7 and 95% confidence interval was from 1.1 to 2.6 (12).
· A study in Europe that looked at 260 children with brain cancer and similar children without the disease found that the risk of disease was higher for children whose parents worked in agriculture or in jobs involving automotive vehicles. This study also found that children with brain cancer were more likely to have mothers who worked in jobs involving use of solvents (13).
· A study in California and Washington interviewed parents of 540 children with brain cancers and parents of more than 800 other children who were similar but did not have the disease. The study found that children with brain cancer were more likely than other children to have had parents who worked in the chemical industry (14).
· A small 1993 study reported an association between childhood brain cancer cases in Missouri children and the use of pesticides in and around the home. Compared to healthy children, brain cancer was nearly five times more likely for children treated with Kwell shampoo, which contains the cancer-causing insecticide lindane, to control head lice; five times as likely if parents used pest strips containing the insecticide DDVP; and five times as likely if they used flea collars on pets (15). Because this was a small study with only 45 cases, the results were regarded as preliminary.
· An early, small, exploratory study in 1979 reported that children diagnosed with brain tumors in the Baltimore area were more than twice as likely to have been exposed to insecticides during household exterminations than children without cancer (16, 17).
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1. American Cancer Society. Cancer Facts and Figures: Special Section on Childhood Cancer: American Cancer Society, 2000. http://www.cancer.org/statistics/cff2000/special.html#categories
2. Ries LAG, Smith MA, Gurney JG, Linet M, Tamra T, Young JL, Bunin GR, eds. Cancer Incidence and Survival Among Children and Adolescents: United States SEER Program 1975-1995. Bethesda, Md.: National Cancer Institute, SEER Program, 1999.
3. Gurney JG, Smith MA, Bunin GR. CNS and miscellaneous intracranial and intraspinal neoplams (ICCC III). In: Ries LAG, Smith MA, Gurney JG, Linet M, Tamra T, Young JL, Bunin GR, eds. Cancer Incidence and Survival Among Children and Adolescents: United States SEER Program 1975-1995. Bethesda Md: Cancer Statistics Branch, Cancer Surveillance Research Program, Division of Cancer Control and Population Sciences, National Cancer Institute, 1999:51-63.
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5. Smith MA, Freidlin B, Ries LA, Simon R. Increased incidence rates but no space-time clustering of childhood astrocytoma in Sweden, 1973-1992: a population-based study of pediatric brain tumors [letter]. Cancer 2000; 88:1492-3.
6. Kaiser J. No meeting of minds on childhood cancer. Science 1999; 286:1832.
7. Bleyer WA. Epidemiologic impact of children with brain tumors. Childs Nervous System 1999; 15:758-63.
8. Preston-Martin S. Epidemiology of primary CNS neoplasms. Neurologic Clinics 1996; 14:273-90.
9. Preston-Martin S, Pogoda JM, Mueller BA, Holly EA, Lijinsky W, Davis RL. Maternal consumption of cured meats and vitamins in relation to pediatric brain tumors. Cancer Epidemiology, Biomarkers and Prevention 1996; 5:599-605.
10. Zahm SH, Ward MH. Pesticides and childhood cancer. Environmental Health Perspectives 1998; 106 Suppl 3:893-908.
11. Kristensen P, Andersen A, Irgens LM, Bye AS, Sundheim L. Cancer in offspring of parents engaged in agricultural activities in Norway: incidence and risk factors in the farm environment. International Journal of Cancer 1996; 65:39-50.
12. Pogoda JM, Preston-Martin S. Household pesticides and risk of pediatric brain tumors. Environmental Health Perspectives 1997; 105:1214-20.
13. Cordier S, Lefeuvre B, Filippini G, Peris-Bonet R, Farinotti M, Lovicu G, Mandereau L. Parental occupation, occupational exposure to solvents and polycyclic aromatic hydrocarbons and risk of childhood brain tumors (Italy, France, Spain). Cancer Causes and Control 1997; 8:688-97.
14. McKean-Cowdin R, Preston-Martin S, Pogoda JM, Holly EA, Mueller BA, Davis RL. Parental occupation and childhood brain tumors: astroglial and primitive neuroectodermal tumors. Journal of Occupational and Environmental Medicine 1998; 40:332-40.
15. Davis JR, Brownson RC, Garcia R, Bentz BJ, Turner A. Family pesticide use and childhood brain cancer. Archives of Environmental Contamination and Toxicology 1993; 24:87-92.
16. Gold EB, Gordis L. Patterns of incidence of brain tumors in children. Annals of Neurology 1979; 5:565-8.
17. Gold E, Gordis L, Tonascia J, Szklo M. Risk factors for brain tumors in children. American Journal of Epidemiology 1979; 109:309-19.
