Academic journal article Environmental Health Perspectives

Mortality from Ischemic Heart Disease and Diabetes Mellitus (Type 2) in Four U.S. Wheat-Producing States: A Hypothesis-Generating Study

Academic journal article Environmental Health Perspectives

Mortality from Ischemic Heart Disease and Diabetes Mellitus (Type 2) in Four U.S. Wheat-Producing States: A Hypothesis-Generating Study

Article excerpt

In this ecologic study I examined ischemic heart disease (IHD) and diabetes mortality in rural agricultural counties of Minnesota, Montana, North Dakota, and South Dakota, in association with environmental exposure to chlorophenoxy herbicides, using wheat acreage as a surrogate exposure. I collected data on agricultural land use and 1979-1998 mortality from the U.S. Department of Agriculture and the Centers for Disease Control and Prevention websites, respectively. Counties were grouped based on percentage of land area dedicated to wheat farming. Poisson relative risks (RR) and 95% confidence intervals (CIs), comparing high- and medium- with low-wheat counties, were obtained for IHD, the subcategories acute myocardial infarction (AMl) and coronary atherosclerosis (CAS), and diabetes, adjusting for sex, age, mortality cohort, and poverty index. Mortality from IHD was modestly increased (RR : 1.08; 95% CI, 1.04-1.12). Analyses of its two major forms were more revealing. Compared with low-wheat counties, mortality in high-wheat counties 2from AMI increased (RR = 1.20; 95% CI, 1.14-1.26), and mortality from CAS decreased (RR = 0.89; 95% CI, 0.83-0.96). Mortality from AMI was more pronounced for those < 65 years of age (RR = 1.31; 95% CI 1.22-1.39). Mortality from type 2 diabetes increased (RR = 1.16; 95% CI, 1.08-1.24). These results suggest that the underlying cause of mortality from AMI and type 2 diabetes increased and the underlying cause of mortality from CAS decreased in counties where a large proportion of the land area is dedicated to spring and durum wheat farming. Firm conclusions on causal inference cannot be reached until more definitive studies have been conducted.

Key words: chlorophenoxy herbicides, clofibrate, coronary atherosclerosis, C-reactive protein, diabetes, ischemic heart disease, myocardial infarction. doi:10.1289/ehp.8352 available via http://dx.doi.org/[Online 6 October 2005]

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A series of International Agency for Research on Cancer multinational studies of workers involved in the production of chlorophenoxy herbicides and chlorophenols indicated excess mortality from cancer, ischemic heart disease (IHD), and possibly diabetes in association with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure (Flesch-Janys et al. 1995; Hooiveld et al. 1998; Kogevinas et al. 1997; Vena et al. 1998). Chemical production workers exposed to TCDD are simultarteously exposed to much higher levels of the commercial chemicals being produced, such as chlorophenoxy herbicides and chlorophenols (Remillard and Bunce 2002). Results from the cancer mortality study among chlorophenoxy herbicide production workers, some of whom were exposed to TCDD or higher chlorinated dioxins (Kogevinas et al. 1997), were similar to those reported in an ecologic mortality study of cancer among residents in rural, agricultural counties of Minnesota, Montana, North Dakota, and South Dakota potentially exposed to chlorophenoxy herbicides and/or contaminants (Schreinemachers 2000). This similarity of results led to the question of whether increased mortality from IHD and diabetes observed among the chlorophenoxy herbicide production workers (Vena et al. 1998) might also be observed among residents of agricultural counties of Minnesota, Montana, North Dakota, and South Dakota, where the major field crops spring and durum wheat have been treated predominantly and long term with chlorophenoxy herbicides (Lin et al. 1995).

The chlorophenoxy herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA) have been widely applied in the United States since World War II and are used for broadleaf weed control in wheat farming and maintenance of home lawns and parks, rights-of-way, and road sides (Short and Colborn 1999). 2,4-D used for home lawn maintenance is likely to be found in residential carpet dust up to 1 year after application (Nishioka et al. 1996). Chlorophenoxy herbicides are present in agricultural and urban streams and in the atmosphere [U. …

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