The Frequent Flying Link To Cancer

December 31 2000

A report in The Lancet found higher rates of certain cancers among jet pilots and crew members. Now, the authors of that study report that this increased cancer risk is due to chromosome damage caused by excessive exposure to ionizing radiation from the sun.

The form of cancer found to be most increased among the flight crews is acute myeloid leukemia, which is very often fatal, with an average survival time of 3 to 4 years following diagnosis. Even in patients who experience complete remission, recurrence is common.

The disease develops rapidly, with symptoms including:

  • Anemia
  • Fever
  • Bleeding
  • Swelling of the lymph nodes

Immature leukemia cells continue to divide in the bone marrow, which leads torapid death if left untreated. It affects granulocytes and monocytes, white blood cells that destroy bacteria and some parasites.

In the current report, researchers note that they found damage to chromosome 7 in 4 out of seven (57%) aircrew members with the cancer, in comparison with only 81 of 761 cases (11%) of the cancer among non-flight crew members.

The researchers conclude that “Our results indicate that deletions or loss of the long arm of chromosome 7 in myelodysplasia and acute myeloid leukemia could be an indicator of previous exposure to ionizing radiation”.

This is not the first time that radiation exposure has been linked to leukemia. People in Japan, exposed to the nuclear bomb radiation have been found to have higher rates as well.

The Lancet, December 23, 2000; 356

What is Chromosome 7

Reviewed April 2008

Humans normally have 46 chromosomes in each cell, divided into 23 pairs. Two copies of chromosome 7, one copy inherited from each parent, form one of the pairs. Chromosome 7 spans about 159 million DNA building blocks (base pairs) and represents more than 5 percent of the total DNA in cells.

Identifying genes on each chromosome is an active area of genetic research. Because researchers use different approaches to predict the number of genes on each chromosome, the estimated number of genes varies. Chromosome 7 likely contains about 1,150 genes. These genes perform a variety of different roles in the body.

Genes on chromosome 7 are among the estimated 20,000 to 25,000 total genes in the human genome.

How are changes in chromosome 7 related to health conditions?

Many genetic conditions are related to changes in particular genes on chromosome 7. This list of disorders associated with genes on chromosome 7 provides links to additional information.

Changes in the structure or number of copies of a chromosome can also cause problems with health and development. The following chromosomal conditions are associated with such changes in chromosome 7.


Changes in the number or structure of chromosome 7 occur frequently in human cancers. These changes are typically somatic, which means they are acquired during a person’s lifetime and are present only in tumor cells.

Many forms of cancer are associated with damage to chromosome 7. In particular, changes in this chromosome have been identified in cancers of blood-forming tissue (leukemias) and cancers of immune system cells (lymphomas).

A loss of part or all of one copy of chromosome 7 is common in myelodysplastic syndrome, which is a disease of the blood and bone marrow. People with this disorder have an increased risk of developing leukemia.

Studies suggest that some genes on chromosome 7 may play critical roles in controlling the growth and division of cells. Without these genes, cells could grow and divide too quickly or in an uncontrolled way, resulting in a cancerous tumor.

Researchers are working to identify the genes on chromosome 7 that are involved in the development and progression of cancer.