Children who have been exposed to household insecticides and professional extermination methods within the home are three to seven times more likely to develop non-Hodgkin lymphoma (NHL) compared with children who have not been exposed to pesticides.

These are the results of a study published in the December 1 issue of the journal CANCER, an international publication of the American Cancer Society.

The study indicated that a child's risk of developing NHL was similar for both maternal exposure to pesticides during pregnancy (in utero) and direct (postnatal) exposure to pesticides.

Significant variations in risk were associated with various NHL morphologies. For instance, the use of household insecticides increased the risk of lymphoblastic lymphoma by 12.5 times.

The term "pesticides" refers to a group of chemicals that have in common their ability to kill insects, plants, mammals (particularly rodents), or fungi.

"A limited number of these compounds may be capable of inducing lymphoma, particularly when used around the home," comments chief researcher Jonathan D. Buckley, M.B.B.S., Ph.D., from the Department of Preventative Medicine at the University of Southern California in Los Angeles.

Lymphoma, the third most common childhood malignancy, occurs at a rate of 21.7 per million in children age { 15 years. Approximately 60% of these cases are NHL.

In the current study, the Children's Cancer Group evaluated the correlation between home pesticide use or occupational exposure to pesticides and the incidence of NHL in a pediatric study sample.

The study included children and adolescents age { 20 years who were diagnosed with NHL between February 1986 and June 1990. Tumors were classified according to cell type (predominantly B-cell or T-cell).

Telephone interviews with the participants' mothers included questions regarding occupational and home exposure to pesticides around the time of pregnancy and direct exposure of the child to pesticides.

From a total of 268 NHL pediatric cases examined, 49 of the patients had lymphomatous leukemia, whereas the other 218 patients were diagnosed with various NHL morphologies, including lymphoblastic subtype (38%), Burkitt lymphoma (28%), undifferentiated (non-Burkitt) lymphoma (12%), and large-cell NHL (19%).

Frequency of household insecticide use by the mothers around the time of the pregnancy (in utero) was associated with a 2.62-fold greater risk of NHL for limited applications (1-2 days per week), compared with a 7.33-fold greater risk for regular use (on most days).

Professional home extermination was related to a 3-fold greater risk for developing NHL. Direct (postnatal) exposure of the child to pesticides was associated with a 2.4-fold greater risk, whereas occupational exposure and the use of pesticide sprays in the garden demonstrated an increased risk, although not statistically significant.

When the researchers focused their analysis on the association between different types of pesticide exposure and the development of different NHL morphologies, they observed the risk for developing lymphoblastic lymphoma was 12.5 times greater after a child's exposure to household insecticide use.

The risk of developing Burkitt lymphoma was observed to be 9.6 times greater after occupational exposure to pesticides. The risk for developing large cell lymphoma or Burkitt lymphoma was 6.7 and 8.0 times higher, respectively, after professional insect extermination.

The authors note that the most statistically significant correlation between exposure to pesticides and the risk for developing NHL were observed for those children who were directly exposed to pesticides.

The risk for developing lymphoblastic subtype lymphoma and large cell non-Hodgkin's lymphoma was 10.9 times and 6.5 times greater, respectively, for these children compared with children who have not been exposed to pesticides.

The researchers also noted a 7.1 times greater risk for Burkitt lymphoma among these children. Overall elevations in the risk associated with pesticide exposure were present for both the younger (age { 6 years) and older (age } 6 years) study participants.

Due to the small number of cases studied and the difficulties in accurately determining the duration and intensity of pesticide exposure, the investigators stress that the findings of this study should be interpreted with caution, and should be further examined in subsequent studies involving larger study samples.

"Pesticide Exposures in Children with Non-Hodgkin Lymphoma," Jonathan D Buckley, M.B.B.S., Ph.D., Anna T. Meadows, M.D., Marshall E. Kadin, M.D, Michelle M. Le Beau, Ph.D., Stuart Siegel, M.D., and Leslie L. Robison, Ph.D., CANCER 2000; 89:11.

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11/26/01