Environmental Health
Perspectives Volume 110, Number 9, September 2002
Critical Windows of Exposure to Household Pesticides and Risk of
Childhood Leukemia
Xiaomei Ma,1 Patricia A. Buffler,1 Robert B.
Gunier,2 Gary Dahl,3 Martyn T. Smith,1
Kyndaron Reinier,1 and Peggy Reynolds2
1School of Public Health, University of California,
Berkeley, California, USA; 2Environmental Health Investigations
Branch, California Department of Health Services, Oakland, California,
USA; 3Stanford University School of Medicine, Stanford,
California, USA
Abstract
The potential etiologic role of household pesticide exposures was examined
in the Northern California Childhood Leukemia Study. A total of 162 patients
(0-14 years old) with newly diagnosed leukemia were rapidly ascertained
during 1995-1999, and 162 matched control subjects were randomly selected
from the birth registry. The use of professional pest control services at
any time from 1 year before birth to 3 years after was associated with a
significantly increased risk of childhood leukemia [odds ratio (OR) = 2.8;
95% confidence interval (CI), 1.4-5.7], and the exposure during year 2 was
associated with the highest risk (OR = 3.6; 95% CI, 1.6-8.3). The ORs for
exposure to insecticides during the 3 months before pregnancy, pregnancy,
and years 1, 2, and 3 were 1.8 (95% CI, 1.1-3.1), 2.1 (95% CI, 1.3-3.5), 1.7
(95% CI, 1.0-2.9), 1.6 (95% CI, 1.0-2.7), and 1.2 (95% CI, 0.7-2.1),
respectively. Insecticide exposures early in life appear to be more
significant than later exposures, and the highest risk was observed for
exposure during pregnancy. Additionally, more frequent exposure to
insecticides was associated with a higher risk. In contrast to insecticides,
the association between herbicides and leukemia was weak and nonsignificant.
Pesticides were also grouped based on where they were applied. Exposure to
indoor pesticides was associated with an increased risk, whereas no
significant association was observed for exposure to outdoor pesticides. The
findings suggest that exposure to household pesticides is associated with an
elevated risk of childhood leukemia and further indicate the importance of
the timing and location of exposure. Key words: case-control studies,
child, herbicides, insecticides, leukemia, pesticides. Environ Health
Perspect 110:955-960 (2002). [Online 14 August 2002]
Address correspondence to X. Ma, School of Public
Health, University of California, Berkeley, CA 94720-7360 USA. Telephone:
(510) 643-3958. Fax: (510) 643-1735. E-mail:
xmma@uclink4.berkeley.edu
We thank J. Feusner, K. Matthay, S. Month, V. Crouse, K.
Leung, and V. Kiley for assistance with recruiting patients and M. Does
for supervising fieldwork.
The study was supported by grants from the National
Institute of Environmental Health Sciences (PS42 ES04705 and RO1 ES09137).
X.M. was supported by a grant from the Centers for Disease Control and
Prevention (T01/CCT917644-01).
Received 14 November 2001; accepted 12 March 2002.
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