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MORTALITY FROM ACUTE MYOCARDIAL INFRACTION IN SPRING AND WINTER WHEAT PRODUCING U. S. STATES
Citation:
SCHREINEMACHERS, D. M. MORTALITY FROM ACUTE MYOCARDIAL INFRACTION IN SPRING AND WINTER WHEAT PRODUCING U. S. STATES. Presented at International Society for Environmental Epidemiology Annual Meeting, Paris, FRANCE, September 02 - 06, 2006.
Description:
Introduction: Chlorophenoxy herbicides are widely used in the U.S. for maintenance of home lawns, parks, road sides, and for broadleaf weed control in wheat farming. Approximately 90% of spring wheat acreage is treated with predominantly chlorophenoxy herbicides, in contrast to winter wheat with only 30% of its acreage treated. Chlorophenoxy herbicides are present in the atmosphere. Their concentrations are the highest at time and location of application. Residents of high-wheat counties may be exposed to higher environmental levels than residents of low-wheat counties. Previously increased mortality from acute myocardial infarction (AMI) was reported for high-wheat counties in spring wheat producing states. In the present study AMI mortality in spring and winter wheat states is compared, with emphasis on differences among age groups.
Methods: Information on AMI deaths during 1979-88 and 1989-98 in rural agricultural counties of four spring wheat states (Minnesota, Montana, North Dakota, South Dakota) and two winter wheat states (Kansas, Nebraska) was obtained from the CDC website. Chlorophenoxy herbicide use by county was not available. Therefore, percent of a county¿s land area dedicated to wheat farming during 1970-1979 (obtained from the USDA website), was used as a surrogate exposure measure. AMI mortality rates in combined high-wheat and combined low-wheat counties with respectively ¿25% and <25% of their land dedicated to wheat farming, were compared using age-standardized rate ratios (SRR) and 95% confidence intervals based on the Poisson distribution.
Results: Increased AMI mortality was observed for most combined high-wheat counties during 1989-1998, as indicated by the following SRRs: Kansas, men 1.20 (1.11, 1.29), women 1.00 (0.91, 1.10); Nebraska, men 1.36 (1.02, 1.81), women 1.44 (1.01, 2.06); combined spring wheat states, men 1.30 (1.22, 1.37), women 1.27 (1.18, 1.37). SRRs for 1979-1988 mortality were lower. Although AMI mortality rates decreased for younger ages, the SRR increased as shown for the 1989-1998 mortality among men in the combined spring wheat states: age 65-85+, SRR 1.27 (1.19, 1.35); age 45-64, SRR 1.35 (1.18, 1.55); age 25-44, SRR 1.72 (1.12, 2.65).
Discussion: Given that chlorophenoxy herbicide use started after World War II, prenatal exposure, age at first exposure, and lifetime exposure, estimated from age and year of death, may contribute to interpretation of the results. More definitive studies should verify that low-dose, environmental exposures to chlorophenoxy herbicides and/or contaminants can cause an increase in AMI mortality.
Disclaimer: This is an abstract of a proposed presentation and does not reflect EPA policy.