Children, Cancer & The Environment Main Page Common Causes The Most Common Cancers Protecting Your Children Q&A

Leukemia

Leukemia is a cancer of white blood cells. It is the most common cancer in children, responsible for more deaths than any other form of childhood cancer. From 1977 to 1995, U.S. rates of childhood leukemia rose about 1 percent each year. In recent years, however, improved treatments have greatly reduced deaths from this disease.

Because it is so common, childhood leukemia has been extensively studied. The research points to these environmental factors as likely to be the most significant:

• Ionizing radiation: Ionizing radiation is a known cause of childhood leukemia. The association with X-rays is particularly strong. Today, prenatal exposure to X-rays has been drastically reduced, as pregnant women receive ultrasound screening instead. However, exposure to X-rays after birth has been shown to increase the risk of childhood leukemia. Radiation from nuclear power plants has also been linked to leukemia.
  
  
• Pesticides: Several studies link parents' and children's exposure to pesticides to childhood leukemia. Studies have found correlations with household use of pesticides, especially when multiple products were used. For instance, a study by the National Cancer Institute found that the risk of childhood leukemia increased nearly four times when household pesticides were used at least once a week. The risk increased more than six times when pesticides were used in the garden at least once a month. Links have also been found with the use of weed killers in the yard and insecticides and pest strips in the home.
  
  
• Solvents: Maternal and paternal exposure to solvents has been linked to childhood leukemia, with the risks especially strong when parents work at certain jobs, including metal work and painting, as well as in motor-vehicle repair and the personal-care and chemical industries. Elevated risk of leukemia has been reported among children of parents exposed to mixed solvents, chlorinated solvents, and three specific chemicals: benzene, carbon tetrachloride and trichloroethylene (TCE). With benzene, the link is particularly strong.
  
  
• Electric and magnetic fields (EMFs): There is contradictory evidence about the role of EMFs in childhood leukemia. But there are many ways to measure these fields, which could account for the discrepancies.
  
  
• Radon: Radon is a naturally occurring radioactive gas that gets into homes from materials underneath houses, such as soil or rocks, or from water piped into the houses. Evidence is contradictory about its role in childhood cancer.
  
  
• Smoking: Again, there is conflicting evidence about whether smoking by parents is linked to childhood leukemia.

Cancers of the brain and central nervous system

Cancers of the central nervous system are the second most common form of cancer in children. These cancers, which may involve the brain or the spinal cord, are most common in children under seven. Childhood brain cancers have been increasing: from 1973 to 1994, the number of reported brain cancers in children under 15 increased 1.8 percent each year. Although some argue that the increase results from improved detection, possibly because of increased use of MRI (magnetic resonance imaging), others believe the increase in cases is real, since brain tumors do not go undetected for very long, regardless of the method used.

Sadly, the improvements in treatments that have occurred for many childhood cancers have not been achieved for brain cancer. In fact, the proportion of cancer deaths in children from brain cancer has doubled in the last 25 years. Moreover, the quality of life of survivors of central nervous system cancers may also be worse than that of other common kinds of childhood cancer.

We know less about causes of brain and central nervous system cancers than we do about leukemia, although one cause -- ionizing radiation -- has been established. But many studies have implicated pesticides. For instance, one study in Los Angeles found that household use of antiflea or -tick products on dogs or cats was associated with a 70 percent increase in the risk of brain cancer, particularly for children under five. A smaller study in Missouri found that children with brain cancer were nearly five times more likely than healthy children to have been treated with lindane shampoo to control head lice, and also five times more likely to live in a home where pest strips were used to control insects or have a pet with a flea collar that releases insecticides.

In addition, parents who work in the following areas have been shown to have a higher likelihood of having a child who develops a brain tumor: agriculture, automotive repair and the chemical industry, as well as any field that involves the use of solvents. Some scientists believe that N nitroso compounds, which are formed in the stomach when people eat meats that have been preserved with sodium nitrite, may also contribute to brain cancer. Bacon, ham, bologna, salami and hot dogs often contain sodium nitrite.

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last revised 4.10.02